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therealpinto GRM+ Memberand Reader
11/18/18 10:07 a.m.

Does it make sense to make a car slower?

Usually not. But this time there is - I hope - reason to do just that. Maybe not a 100% sound and valid reason, but nonetheless, a reason.

Well actually maybe two reasons. The first is that this might be the single most important car project I have ever gotten into. It might prove to be the most important one I'll ever be involved in. Why? It's my daughters car, and my chance to invite her into the fantastic world that the auto hobby is. 

Some background, unless that bores you...she's born in 2004 so when I write this, she has quite recently turned 14. But she has always joined me on different car events, from before she could walk. She's been helping out at shows, handing people entrance passes, you know the stuff. A very strong memory is from when she was about 3 years old, and had been the entire day at a car show with me. Later the same night we were running a "run what ya' brung" dragrace, but my wife picked Kajsa (yes, that's her name) up earlier to get to bed in time. When she realized she was missing the race, she was devastated. Of course, my wife turned the car around so they both got to watch the race.

In Sweden the legal driving age is 18, so that's a long wait for someone young, that wants to get into cars. But there is a loop hole, you are allowed to take a moped license at 15 and that license also gives you the right to drive a tractor.

After the 2nd world war, there was a shortage of farm tractors, and there were rules developed to allow farmers to convert old cars into tractors. It is explained here:


In the 1970's or so, the A-tractor was adopted by youngsters, as a means of transportation. The rules have evolved a bit but the same basics apply. It has a maximum speed of 30 km/h, it has to have a really low range first gear and it can not have a rear seat. 

That is what me and Kajsa are building.

Now, the usefulness of a transport that crawls at 20 mph or so can be debated. But in the cold winter it is a nice alternative. And it's a great chance to learn how to work on cars. 

We have been planning this build for quite some time now, with a number of options. Kajsa, being my daughter, has been very single-minded in demanding that is has to be based on a Ford. The easiest build is based on a pickup truck. Sweden is not a big pickup-country, with small Japanese trucks being the most popular ones. The Ford Ranger is a rebadged Mazda, not that much fun.

The downside with basing the build on a "car car" is that generally it's quite involved. Most people use dual gearboxes to get the low range, and convert the car to something similar to a truck (there are rules stipulating a small truck bed to give enough weight on the driven wheels). Cutting the car up like that means quite a lot of body work. While I need to practice doing that, I would not want to end up with a stranded project like many others.

Next thing, the base car should be reasonably cheap, and not too rare to modify. We had a lead on a 4 cylinder Fox body Mustang - but the rules say the car needs to have a rated towing capacity of at least 1000 kgs. A late Thunderbird felt like the best bet for a long time but Kajsa, for some reason, has always had a soft spot for the Sierra. Probably because of the XR4x4 I had when she was little.

She really wanted to build on something like that. With the XR4x4 long gone (yes, another one of those "I should have kept it"), and the prices of decent Sierras moving up we did not have great hope.

But still I decided to ask around a bit. And an old friend got back to me, saying he had a car, that he could let go of. He warned us that it was quite ratty, not a nice car at all, but available.

So we went out in the woods, hunting for a Sierra, and was greeted by...

...a 1992 (second-to last model year) GT (GT meaning nicer seats and marketing mumbo jumbo). Some dings and dents (the bonnet seems to be attacked by someone with a ball peen hammer), some rust, and obvious signs of someone tracing a fault somewhere, since the interior and ECUs were halfway out. But hey, I had seen worse.

As we asked about the price, it was a no-brainer. 500 SEK or around USD50, not much to loose there. So the deal was struck!


mazdeuce - Seth
mazdeuce - Seth Mod Squad
11/18/18 10:11 a.m.

This should be cool. I love this loophole in the laws that lets younger people drive. 

therealpinto GRM+ Memberand Reader
11/19/18 1:17 a.m.

Thanks Seth! 

We closed the deal in the beginning of the summer, with other obligations demanding their fair (or un-fair) share of life. But we promised to take the trailer and go get the car "some day".

While waiting, me and Kajsa started throwing ideas on the design around. We looked for inspiration from other Sierra builds and came up with two design sketches.

The rules say that the truck bed must be centralized over the rear axle, and must not be covered. The first pickup like sketch is the easiest to build. The lower sketch would mean that the rear window would have to be in the C-pillar with the rear part of the cab being open.

Much thinking went on but Kajsa really wanted us to go for the second version so that was the plan.

At one point of the summer the seller (my buddy) dropped me a line saying he had ad empty trailer going from where the car was stored, and offered to load it up and drop it off at our house. Cool!

As we got it home, first step was to wash it off and assess the canvas a bit more.

We found a decent car but a very soft/mushy clutch, an engine that would light up the oil pressure light at idle and all brake warning lights (ABS and low brake fluid/brake fault) were on. There was no brake servo assistance, this car uses the Teves system with an electric booster. With ABS ECU halfway removed, it was quite obvious that someone has been chasing the brake problem - possibly the cause for parking the car.

The engine didn't bother me too much - I have Pintos to swap in if need be. And the drive train would need work anyway to meet the speed limit requirements.

But it would be nice to know if the brakes would work. ABS would be nice to have, but if all else fails I do have a non ABS brake booster and mastercylinder for a Sierra (I think!).

I gave Kajsa the basics on chasing electrical faults, and aided by some Teves manuals and how-to's we spent some hours working our way into the system. All electrics seemed to check out and that pointed to the possibility of a seized pump motor for the electric brake booster. Sure enough, the terminals measured out as a short.

Years ago I was planning use this kind of brake booster in the Capri so I had gotten some parts. Quite recently I tried to clear out the garage and decided that these old ABS parts were gonna go. But they only made it as far as to the "going to be recycled bin". Still there, so we had an extra master cylinder with booster to work with.

Swapping just the motor seemed to be the easiest way, and it worked!

The best thing about all that work, was that Kajsa helped through all the steps, I don't think I spent 5 minutes on the car without her. That's really nice.


BirgerBuilder Reader
11/19/18 2:20 p.m.

Love this plan. I really hope my kids want to build stuff like this in a few more years. 


dculberson UltimaDork
11/19/18 2:32 p.m.

This is great. I have a 4 year old at home that I hope is interested in projects with me at 14!!

therealpinto GRM+ Memberand Reader
11/20/18 2:33 a.m.

It's a blessing! What has worked for me is to include my daughter in the activities - not so much the wrenching up until now, but going to car shows, races etc.

With the brakes dealt with it was time to have a look at the engine.

First swap out the flat tire...

...then  drain the oil for a simple oil and filter change. 

The old oil was quite thing and the numerous empty oil cans in the car pointed to possible oil consumption problem. I just wanted to get a new filter on it and get some thicker oil in the engine so we wouldn't risk it seizing when moving in and out of the garage.

It got a mix of my old leftovers, you know the deal - there is often som oil left in the can after an oil change. It was a cocktail of 10-40, 15-40 and 20-50 just to see if the oil light would go out.

It did. That meant we could go around the block (sort of) to see how it all worked. The blue smoke screen is probably a tell tale that the engine is not too happy, and it also has the typical DOHC/I4 slurping sound in the heater, that usually means the head gasket is leaking too. This engine type is known for dropping valve guides so either way, the head needs to be lifted.

But there were more thoughts to be thought. We needed to firm up the plan on the conversion to a tractor.

The rules are quite involved. The thing can do maximum 10 km/h in the lowest gear, at 2/3 of the engine max rpm. And it has to be limited to 30 km/h (+10%) in all gears. The traditional solution has been to use two gearboxes in a row, with one locked in 1st gear, and the other one usually with only first and second. But this means you crawl at 30 km/h at top rpm - that's not nice.

Quite recently the use of electronic speed limiters has been accepted, a device that measures speed and cuts spark or fuel when 30 km/h is reached. This means you can use more gears and keep the rpms down.

I whipped together an Excel sheet to make calculations on different ways to solve this. One goal was trying to avoid using two gearboxes, since it is quite bulky and you tend to run into shifting problems. A pickup truck gearbox with a low range gear seemed quite good, but most low ranges are around 2:1 and that means you need a really low rear axle ratio.

However, when looking at those gearboxes, and the rules, something dawned;

"Unless at least 60% of the curb weight is on the driven wheels, a ballast bed is mandatory"

What if all four wheels are driven? No bed, no need to cut the body. I am far from the first one to think of this, I will admit.

Now, as evidenced by the red beast (!) above, the Sierra was available with 4wd. That would be a sweet solution!

The Sierra 4wd gearbox is quite similar to for example the Mazda B2600 4wd gearbox so we thought about just taking the engine and gearbox from one of those. It would still need axle ratios around 4.3:1. Now...the newer Ford Scorpio (1995-98) has the same kind of rear differential as the Sierra, but with larger wheels, Ford lowered the ratios. I have two of them...with a 4.27:1 ratio. That leaves the front diff. The Mazda trucks are available with a 4.3:1 ratio. Should work.

Now we had to think a bit. Do we look for another car, a Sierra 4x4, to build on? Just days after we closed the deal on this one, a 4x4 had been for sale locally (well, a 2hr drive away). But it was gone. 

As usually is the case, I had the feeling that when we weren't looking, the 4x4s were everywhere. Now we started asking around and after a couple of weeks we had a car lined up. At the same time, someone said I should ask one of the dragracers (Hemi Demons anyone?), who might have stuff laying around.

The complete car looked pretty good but Kajsa objected. It's not a GT, and she already was a bit in love with the blue car.

So we decided on the hard way, collect 4x4 parts shattered around the Dodge sheds (not the cars, wooden sheds filled with Dodge parts), and try to convert the GT into a 4x4. The entire front end (engine cross member, steering rack, track control arms, spindles and struts are different).


therealpinto GRM+ Memberand Reader
11/21/18 1:39 a.m.

With the 4x4 route pretty set, I returned to my thoughts on drive train.

Some boundary conditions were in my head;

- gasoline engine (more fun, I don't like the smell of diesel, I don't like the sound of a diesel)

- preferably a Ford engine

Not too limiting perhaps but there also was the issue of the front diff. All Sierra 4x4s have the front diff attached to the oil pan (alloy), on the right hand side, with a drive shaft running through to the left hand side. Using a complete oil pan with diff would make thinks loads easier and that basically leaves 4-ish engine choices;

A. Sierra Cosworth 4x4 (yeah, right)

B. Pinto (same block as the YB from the Cosworth, I have 2-3 blocks...and heads...and...)

C. Cologne V6 (2.8 or 2.9, or versions of those)

D. I4 DOHC 2.0, the engine already in the car

At first I was well set on building a Pinto and using my tuning experiences to make something low revving, with good low speed torque. But it has the exhaust on the right hand side over the diff. And I would need a Cosworth 4x4 oil pan.

As the pile of parts we collected from the MoPar guy contained an I4 sump and front diff (actually, the pile contained a "complete" engine in parts but we forgot to take the head), I started thinking about that one again. I can't say I really like that engine, mostly because it's rather low revving, and boring. But hey, this is a tractor.

Instead of converting a Pinto into that, maybe we might bite the bullet and try to rebuild the I4.

This also meant that using the Sierra front diff seemed very tempting. The 4x4 version has a 3.9:1 ratio, can we find a 4x4 gearbox or transfer case with a low enough low ratio to make it work?

I almost wore out my fiber connection researching transfer boxes - something I had never given a thought before. I used our national U-pull it scrapyard site to search for transfer boxes and gearboxes. The database has a neat feature where you can search for a part regardless of make, very handy. Scrolling through 50 pages of transfer boxes is fun. In a way.

The Suzuki Samurai seemed like a candidate, if fitted with a crawler kit. Or the Lada Niva, where you can build our own crawler kit, using some parts from another Lada gearbox (and possibly some Russian witchcraft). Both of those solutions are great for those having parts all around but what would I do with another second hand Lada gearbox missing 3rd gear?

Finally, Land Rover may have delivered the solution. The LT230 transfer case is available with a low ratio of 3.2:1 or thereabouts (and the high is also low, 1.21:1 for later models). With a 3.9:1 final drive ratio, it would just work, according to my calculations. 9.52 km/h at the required engine speed in 1 st gear low.

Of course, the LT230 is designed to be attached to various Land Rover gearboxes. Not Ford gearboxes, not separated from the gearbox. Now I learnt a new term in the 4x4 world, "divorce mounting" a transfer box.

For some time, I was a bit worried that Mrs therealpinto would be worried with me searching the Internet using the word "divorce". Then I remembered, I am the car crazy guy here and if someone would be looking for that, it's probably her - not me. :-)

As always, there are people who have done this so there are some options. 

At this point in time, the LT230 should be delivered tonight.

But there's more. We need to sort the electronic speed limiter. More on that later.


RossD MegaDork
11/23/18 8:08 p.m.

Neat project. One thing that came to mind is using a FWD gear box and engine, welding the diff, turning everything sideways so its longitudinal again and send the axle shaft back as a driveshaft. Rock climbing buggy style.

fiesta54 Reader
11/24/18 10:26 a.m.

Wow, this is interesting.  As far as the body design goes, maybe consider removing the center section of the cab and sliding the rear forward.  That was you can reuse the glass that is already there. 

therealpinto GRM+ Memberand Reader
11/28/18 7:36 a.m.
RossD said:

Neat project. One thing that came to mind is using a FWD gear box and engine, welding the diff, turning everything sideways so its longitudinal again and send the axle shaft back as a driveshaft. Rock climbing buggy style.

Yeah, I had that in mind. But it is also vital to be able to drive 30 km/h at low revs and my calculations showed that top gear would be around 10:1 in total ratio, meaning we would need to do around 2700 rpm at 30 km/h. Not crazy high but still a bit higher that I wished for.

With the 4x4 plan, our idea is not having to redesign the body at all. While it would be cool to do a good looking "ute" it will probably save a lot of time not having to.

Back to the speed limiter for a bit of background. As I said above, the use of an electronic device to limit speed is generally accepted now. There are some ready made solutions available, that measure speed from a wheel or the propshaft, and then cut the power to either the coil or the fuel pump to limit speed.

But as you know, riding a rev limiter is a bit tiring. Pops and bangs are cool for a short time but in the long run, something we would like to avoid.

For years I have been in contact with a guy developing the MaxxEcu engine management system, something that started off as a Megasquirt alternative but in recent years has moved in a somewhat different direction. We chatted about other things when we drifted over to what their more recent systems can do. It now has drive-by-wire (or throttle by electric wire?) capability, and it has a lot of settings for working with that. We spoke about the possibility to limit speed with a DWB throttle - should be perfectly doable, and also should give a very soft limiter (if mapped correctly).

Now, swapping to an aftermarket ECU is probably one of the biggest overkills ever, but it sounded fun. So we decided to give it a try.

So far, I have the ECU with wiring harness, and I have a throttle pedal and throttle body from a Volvo V70 to try to adopt to the Sierra.

Will it work? Not sure. There are hurdles to jump, but if all else fails we can just use a regular regulator :-)

A free-standing DBW controller may be way easier but in most cases is not cheaper that what I have here. We'll see what works.

But before we start on that, we need to do some work to the body. If nothing else, for motivation!


therealpinto GRM+ Memberand Reader
11/30/18 1:03 a.m.

Bodywork, yes...

That tends to take time for me so I wanted to get that started and mostly finished as soon as possible.

While we decided not to make it into a pickup truck, we still had some crusty wheel arches to deal with.

And then an ad for some wheels popped up. Sometimes I am a sucker for new wheels...especially Compomotive, they usually have that "thing". The first plan for this car was maybe to use the Escort Cosworth wheels I had on my Capri, before I swapped to the XXRs. But EsCos wheels are starting to gain a bit in value and I was not sure I wanted them to possibly degrade a bit here. Now there was an ad for Compomotive MO, five spokes, 8x17" in ET15. By chance, the perfect fit on the Capri for the future?

They would also suit the image Kajsa had in mind for the Sierra. And when the guy selling (a hardcore Cosworth fan) agreed to take my EsCos wheels as part exchange, I couldn't say no. I could have gotten more money for the EsCos wheels in other places but simplicity should not be understated.

So trial fit.

Rears are almost there, front...not so much. Rolling the arches, or flares? Flares, or rolling the arches?

I am a flared arches guy, have always been...but rolling may be easier. Or not... We debated for weeks before we found pictures of a Sierra with "JDM" flares, that looked nice. The helpful guy shared the part numbers so we could order the same parts.

That's more like it! Some lowering and it will be fine.

The rears might possibly need a spacer to fill the arches properly but that's for later. Now we need to clearance the sheet metal under the plastic too.


FunkyCricket New Reader
11/30/18 8:19 a.m.

This is super cool, and I see your daughter has MazDuece's taste in safety foot wear.

therealpinto GRM+ Memberand Reader
12/3/18 1:15 a.m.


Yeah, we went out and bought her some leather boots for the real wrenching and just yesterday she did her own shopping list;

- brake fluid
- safety goggles
- ear protection
- bondo
- flap disc

She has been using a set of goggles and ear protection from my shelf but they are not good enough any more. We really should get her a welding mask too...


FunkyCricket Reader
12/3/18 1:07 p.m.

I hope my boys are as interested at her age. Keep us updated! 

therealpinto GRM+ Memberand Reader
12/3/18 2:30 p.m.

With the flares marked we could turn our attention to sorting the rusted rear arches, as seen above.

Conveniently, the flares cover most of the rust, it will be cut away to make room for the wheels. But the right "dog bone" behind the rear door needed sorting. I got some repair panels before we decided to go for flares so we might as well use them.

Marked for cutting.

Child labour cleaning it up :-)

We had to make a bit for the rocker/sill too, and Kajsa enjoyed working with sheet metal. "I might be a panel beater!"

This was her first real work with an angle grinder and the finger sander, but she's getting the hang of it.


therealpinto GRM+ Memberand Reader
1/16/19 2:24 a.m.

Work is sort of progressing in bursts, not huge ones but all progress is welcome.

The right rear arch is mostly fixed, new metal welded in, the arch modified for clearance and the bad part of the sill replaced. 

Kajsa did try some welding too but really, starting with body panels is a bit tough. We need to start practicing on some scrap metal first.

We still need to remove a spring to see if the clearance for the wheel is anywhere near enough but that's for next time. We also fixed a strange rust hole in the right front fender, and then added some filler (because I am still not good enough at getting the metal really smooth).

In parallel I have been looking more into the mechanics. I got a kit from the UK to divorce mount the LT230 transfer box (really only an input shaft with flange), and prepared that. I started looking for possible clearance issues in the transmission tunnel. We may need to make some room behind the gearbox, we need to remake the transmission cross member but that was expected.

One thing I had omitted though was starter location. On rwd Sierras it is on the right side, 4x4 Sierras have it on the other side (since the front drive shaft passes exactly where the starter lives). The bellhousing is not removable and the starter of course sits in the bellhousing.

The Sierra 4x4 gearboxes have the transfer case as integrated casting so it's not really easy to use the LT230 transfer box with one of those. Probably not impossible with some machining though. 

So I looked back at the regulations and as it is stated, you need 60% of the curb weight on the driven wheels in order not have the pickup bed. How is the weight distribution for starters?

The floor is maybe not 100% level but it's not that bad. Look at this! That's the car with almost no fuel, no driver and some boxes of small stuff in the boot. The driver is 75 kg (standard weight used), around 40 kg of fuel, the transfer box is 50 kg. That would add up to around 1410 kg, so I'd need 60% of that on the rear wheels - 846 kg.

The fuel tank is behind the rear axle so that 40 kg, if I place the transfer box far enough rearwards and guess that the driver weight is split 50/50, I should reach something like 730 kg rear. Move the battery back and it should be around 750 kg. The 100 kg that is missing could well be the divider wall that is needed to make it a 2-seater, and a really, really nice bass speaker enclosure.

So in theory I could keep the car rwd and save some work. 

The transfer box is still needed to lower the gear ratios enough (although an inline reduction gear would be better . but I can't seem to find one with around 3.3 ratio) but it saves a ton of work with the front end.

I need to run the idea by my registration officer though.


Floating Doc
Floating Doc GRM+ Memberand Dork
1/16/19 11:19 a.m.

Fascinating. I'm looking forward to following.

therealpinto GRM+ Memberand Reader
1/17/19 2:14 a.m.

Thanks, a bit stunned by someone thinking it is "fascinating" :-)

The registration officer was not immediately a fan of the weight plan - the Sierra has a maximum rear axle load of 900 kg and he thinks that putting curb weight at 846 kg gives too little room for additional weight. I don't necessarily agree since the only thing the car is allowed to take on as load is one passenger - and that weight will be divided front and rear.

I know the estate versions had a way higher axle load, but I would need Ford to make a statement saying I could use that figure for the combi coupé, if I use estate springs. I will check that but the other option is to just try and lower the overall curb weight.

The plan is to replace both broken bumpers with fibreglass (because Kajsa wants that look), and we might be able to reduce some other stuff. If I could reduce the overall weight by 30-35 kg I think that would suffice. The problem of course is that I need to remove that from the front end of the car, not the rear. 

Moving the battery and the washer fluid tank to the boot is one step. Then maybe remove the air filter box, the headlight washer/wipers, bonnet insulation... A fibreglass bonnet would be a costly option too. We'll see about that.

The 4x4 option is not completely dead either, I might have an older 4x4 gearbox laying around, the type 9 with a removable bellhousing. It could be used to graft the Land Rover transfer box onto with a special bellhousing. But the amount of work, compared to moving weight around, is giganormous!


TED_fiestaHP Reader
1/17/19 6:41 a.m.

   If  you are close on the weight requirements, what would happen if you moved the rear axle forward just a little.   There is some room between the tire and the front of the fender well, little things can start to add up.  Move the battery to the trunk, with heavy cable.  Lighten stuff at the front, and do the opposite at the rear.  Battery mount will need reenforcement, so that is more weight. 

TED_fiestaHP Reader
1/17/19 6:41 a.m.

   If  you are close on the weight requirements, what would happen if you moved the rear axle forward just a little.   There is some room between the tire and the front of the fender well, little things can start to add up.  Move the battery to the trunk, with heavy cable.  Lighten stuff at the front, and do the opposite at the rear.  Battery mount will need reenforcement, so that is more weight. 

therealpinto GRM+ Memberand Reader
1/17/19 7:16 a.m.

That's an interesting idea but more work than I am willing to take on.

I made some research and the V6 Sierra 5-door has an extra 50 kg axle load, and that is the exact same body, rear suspension (except perhaps for springs) as we have. The estates are at 1050 or 1060 kg so I do think we can sort it by just getting the right documents to support that change. If not all the way to 1050 kg, so at least to the 950 of the V6. 


therealpinto GRM+ Memberand Reader
5/22/19 2:29 a.m.

During the winter I managed to get a Ford garage to write a statement on axle weights. I hope it will be enough...

We have moved on with some more body work and as of now, all fenders are cut and roughly shaped.


Front wheel fitment looks good - also with the very 90's body kit temporarily fitted :-)

Last night we removed the rear bumper and the tow bar...

The mounting brackets are properly toast. Not brain surgery to rebuild put I have put the word out for a better tow bar, and have some leads already. The tow bar is a must for the tractor registration, unfortunately.

If we want to get this thing done by September we need to speed up, let's see how that goes. The race car has been taking some time but after the next race (May 25th) we have all the time until August until we race again. In June I am working at the big race here but then things should slow down a bit #famouslastwords


Patrick GRM+ Memberand MegaDork
5/22/19 6:28 a.m.

Make trailer hitch/tow bar out of 1/2” thick steel for weight?

therealpinto GRM+ Memberand Reader
5/22/19 7:45 a.m.

The thought has struck me!

Another option is just filling a standard tow bar structure with concrete. Far easier :-)

With all the things left to do my primary option is to buy a "new" tow bar, trying to spend time wisely. But we'll see.



FooBag GRM+ Memberand Reader
5/22/19 11:56 a.m.

I'm glad to see the update on this project as I had been wondering what was new with it.  I find the whole " car into tractor"  thing highly amusing.

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