The Complete Guide to Ford 8.8 Gear Swaps, or How Do I Put 3.73 Gears in my Foxbody? 

Thanks for your glowing feedback, and thanks for watching!

It’s probably the lowest hanging fruit on a car like this which came with such anemic gears.

Thanks for your affirming feedback. I strive to provide accurate technical info on this channel and it is always nice when a viewer confirms that for other viewers.

Thanks for your kind words. When I get one that needs a clutch rebuild I will make a video showing that.

@@tecmotiondyno It was a great video even without that part. This will really help guide a lot of people to tackle this job and complete it correctly. You have the hands on working knowledge to confidently give facts that many other content sources leave out. Keep up the great work and leaving a lasting knowledge database for people getting into the foxbody.

You are welcome. I’m just glad some of you guys are actually watching this feature film length technical video!

@seeunow44, thanks for the complement. When I started editing this video I realized that there was no way to really show you how to do the job in a 15 minute quicky, but I thought no one would watch what amounts to a feature length film, so it has been a pleasant surprise to see guys actually watching it. I did chapterize it to make it easier to find key parts of the job if you just need a little help or a review while you are doing it. Good luck with your project!

Thank you, when I see it helping guys it makes the effort to produce it seem worthwhile. Thanks for watching!

This car didn’t have a Coyote, but I am with you on that. I have a Coyote aluminator in my street rod and a drive a blown Coyote convertible every day in the summer!

Glad it helped. I’m actually stunned that anyone watched this feature film length DIY video given the attention span people have today, so it’s great to get feedback like this. Feel free to pass it around to anyone else you know that could use it.

I have 4.10’s in my Mark VII and in my Coyote street rod. The Tecmotion Coupe has 4.88’s. Gears should be one of the first changes on cars like this for sure.

You are welcome. Thanks for watching!

Yes, and if you are building a hard hitting drag car, using a 9” style solid spacer is a good idea because really hard launches will further crush that collar, take the pinion preload out, and can result in a failure of the gear set. I actually tore all the teeth off an 8.8 pinion in a drag race because of this problem. It’s not necessary for the average street car though. If you look through this channel there is a video of that pinion failure on here, including in-car from when it happened.

Tecmotion Coupe Breaks the Pinion at Mega Ford Weekend V ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-zyPC9U0Dc0Y.html

Thanks, and thanks for watching!

I hope it helped, and thanks for watching!

I’m glad you liked it. Honestly, when I edited it and felt like I couldn’t cut any more out without omitting important parts of the job and I still had essentially a feature length film, I thought no one would watch! It’s refreshing to see people actually watching it and getting something out of it.

@@tecmotiondyno I totally understand the long video dilemma. But I watched the whole thing and it was great! So don't worry so much about the length of it. As long as it's good, we'll watch 👍

Thanks for watching! Feel free to share it with your friends if you find it useful.

Thanks for your nice feedback, and thanks for watching!

Thanks! When I saw how long this video needed to be in order to be comprehensive I thought no one would watch it, so it is great to see it serving as a legitimate resource.

again, so well done. not rushed and 'hack-ish'. a jewel. @@tecmotiondyno

You are welcome. Hopefully it is proving useful!

If you take your time and have the right tools and facility, you will get a good job.

It is generally easier with the housing out on jack stands, but sometimes you need another guy to sit on one end of it while you crush the crush collar because you can actually lift one end right off the stands if you aren’t careful. When you pull the housing out of a V8 Fox, make sure you have a plan for the brake banjo fitting - you will need a new copper washer at the minimum and sometimes the whole fitting has to be replaced.

@@tecmotiondyno thanks for the tips. This is a 94 so it has rear discs, so I was thinking I can just hang the caliper up out of the way with the rear end out and not have to crack any lines loose.

You’ll be fine with that. The 5.0 Foxbodies run the brake lines down the middle of the car and then to the housing, but yours has the lines on the sides. You are totally going about this the right way in my opinion.

@jasonmiller4279 If you can, try to put 500 miles on it before really abusing it, but it probably doesn’t matter that much. I have literally installed one track side, drove up to the start line, and won an event with it. Thanks for watching and good luck with yours!

Lots of turbo guys run a taller gear like 3.55 with a modular like that. I’m not sure that I would change it, though I usually recommend 4.10’s for a naturally aspirated modular. As far as the differential itself, the stock unit is ok, or the GT500 traction lock with the carbon fiber clutches is a nice 31 spline replacement that is really reasonably priced.

It’s redundant for sure. Occasionally you think you got a nice mark and after you clean everything up you can’t see it or distinguish it from some other mark that appeared after cleaning, so it is a good policy to do both.

Do you mean of the traction lok or doing the gear job with the housing out on the ground?

Yes, the gear setup is the same, though the later ones use a different pinion bearing. The IRS in the Terminators use the same gear setup too, but it is a lot easier to get at the housing if you pull the subframe out.

A transmission swap on jackstands is no fun at any time, and I’m a big guy so I hate working under the dash, so the pedal box swap is also no fun. You’ll still have some of those problems with a gear swap on jackstands, but the gear job requires a wider array of specialized tools and attention to tolerances that are absent from the transmission swap job unless you also did the transmission rebuild. I have a hard time actually recommending that guys do this or any job themselves because there are all kinds of people out there and not everyone should be doing mechanical work. As an example, in the kit car world as shocking as it sounds, the typical guy who attempts a kit car bought his first socket set in conjunction with the project and has almost no real experience. Some of those guys are careful thoughtful workers and get a successful project done, but a lot of them abandon their project and make terrible mistakes that result in junky builds, which is why kit cars have a bit of a bad reputation. There is a stronger sense of accomplishment in doing it yourself, and if you spend your money on tools rather than services you will have something besides the car to show for the job. I’ve tried to give an honest comprehensive look at the job here but ultimately YOU will have to decide if you can do it successfully. There’s no shame in farming this job out to someone who is experienced and well equipped if you decide you can’t handle it. I typically charge $1500 Canadian parts and labor for a Foxbody gear swap, and I typically have the car for three days total if you are shopping the job around and wonder what it should cost. Good luck, and thanks for watching!

@tecmotiondyno right on Matthew! 🙏 ❤️ thank u so much for the response and your input. It's funny because I was going to have a performance shop do it this week rebuild the whole rear ie gears, traction lock seals and axle bearings and the gentleman canceled on me 😔 as I contemplated tackling it myself because I agree with u! 💯 the satisfaction u get after putting the sweat equity in is an amazing feeling! I had no idea what I was capable of after that aod to t5 swap by myself no help and first time. I am going to see if my local auto zone does tool renting and possibly face this one head on! I hope to see u make a video on the traction lock rebuild and axle bearings and seals on the next rear end u do. That is on my list as well just as preventative maintenance! You my friend are awesome 👌 👏 and I thank u kindly!!!! Izzy 🇺🇸

The axle bearings are not a big deal when you have the housing empty - just use a long bar to drive them out like I discuss here, and installation is straightforward with a seal and race driver, just be careful not to drive them in too deep.

@tecmotiondyno right on! I've been at it 3 days now lol haha. It's definitely no fun on jackstands. I honestly wish I would of just removed the whole rear as opposed to working on the concrete ground underneath the car. So far got the new rear axle seals and bearings installed, and trying to tap in the new races with a junky parts store bearing seal kit. They are being stubborn and I noticed the new races are a bit smaller in thickness than the factory ones I punched out. I'm running the Ford performance kit from lmr going from 273s to 355s.. going to replace the clutch packs for the t lok while I've got it out. I would rather be hit with a dead blow hammer 🔨 than pull all this back out again in the future 😆. Did u get lucky with the old pinion shim on the new pinion? And did u use the old shims on the side for the carrier? I'm hoping I find a shop to press on the new bearings for me. Thanks again 🙏 I learn so much from watching your vids. Had no idea how much work was involved in this project.

If you swap ford gears for ford gears and you use the same style pinion bearing, you can normally use the same thickness pinion shim as was used on the set you took out. In fact, that is a Ford Racing procedure, not just a shortcut. The original side bearing shims are a good starting point but they are almost never correct for the new gear set. Figure on adjusting them 3 or 4 times before you get it right. Make sure you turn it over a few times before you take your backlash measurements. Pulling the whole housing is not a bad plan but you will need new copper washers for the brake to body banjo fitting and will have to bleed the brakes after you put it back in.

I have always thought that 3.55 was too timid, even for the highway myself. I am generally biased toward more gear than your average guy out there.

Pretty sure that’s going to happen

Yes, Tecmotion is based in Calgary, Alberta.

That’s what I put in my Lincoln mark VII because it was heavier and an auto. If you are going to be driving it on the highway at 80 mph for an extended amount of time, 4.10 is almost too much though. Otherwise, it was a good choice.

@@tecmotiondyno 80? Lol. 65 here or u get a big tickee

There are places in the western US where 80 is the posted limit. Alberta highway 2 is 70, but that’s more of a suggestion than a hard limit in reality. You can get passed by a heavy truck if you are driving 70!

@@mistersecret88 in NY if your NOT driving 75 + your getting your doors blown off on any hiway here..

@@AwakeDude911 No doubt.

Believe it or not, I edited this video for brevity! I broke the bolts loose “off camera”, though it was done with a 12mm combo wrench.

yeah at the bone yard youll say prayers with a wrench trying to break theses bolts freeeeeee

Here’s something funny about those bolts. One of the most common problems I see in a pre-dyno inspection is the driveshaft bolts actually loose - like remove with fingers type of loose!

@AwakeDude911 Sometimes the thing that is in the way is the mid pipe mount, and that can be removed. I’d have to get a look at yours, but I did a car with a 3550 in it a year or so ago and I’m sure it had the speedo cable installed. I might have some pictures or video of that car if I started digging.

I don’t think I ever promised that! Thanks for watching!

If you were watching, I have the safety glasses in my hand and put them on right before cutting the inner race off the bearing, but thanks for your concerns about my safety. As for work benches - fair enough. All my work benches are covered in junk and bench based power tools, but I have lots of floor space to work on something like this and it is closer to the car.

@sleathers1551 While a full pinion depth setup is part of a comprehensive from scratch gear change, in the special case where you are swapping one properly set up Ford gearset for another, Ford themselves suggest simply measuring the pinion shim that was installed and using a new one of the same thickness. Ford pinions are not marked with a pinion depth like aftermarket ones, and if you choose to do the full setup, like you will need to if replacing a non-Ford gear set, using a non-Ford gear set, or starting with an empty unreferenced housing, you will need special service tool T79P-4020-A or equivalent. The procedure outlined in this video is for replacing one properly set up Ford gear set with another, and is as described in Ford publication IS-1850-0239, Page 7: "Pinion Shim Selection Overview Ford Racing and Ford OEM gears do not use the same pinion depth method of setup as aftermarket gears. Shimming is done to compensate for differences in the machining of the axle housing. If you are removing a Ford OEM gear, the use of the same thickness pinion shim on the new Ford Racing gear, most times will allow you to achieve correct tooth contact pattern with only minor adjustments."