[DiMora]

The Eaton Detroit TrueTrac is installed.

Lots of detail here, so grab a beer if you really want to know how it went. This will be a long one.

It wasn't too bad, but I did have a couple of snags along the way, which I'll detail in case anyone else wants to DIY this mod.

Big Picture: There are two variables one must account for when overhauling a rear end. One is pinion gear depth and the other is backlash. Both settings are changed by using shims between the gears and the bearings and these directly affect how your gears mesh together...AKA your "tooth pattern". Done incorrectly, you can have gear whine or even fluid overheating and gear failure.

Based on what I have learned, I believe it would be a really bad idea for someone to attempt to overhaul a rear end without having seen it done before. For this reason, I spent $40 for a two- DVD instructional video specific to Ford rear ends and I watched it twice:

Video here: Bad Shoe Productions How To Video Series - Ford Transmissions & Rears

The scary "VooDoo" that makes people fear rear ends is reading the "tooth patterns". The video I purchased came with pictures that explain how to "read the patterns".

When you pull your True-Trac out of the box, it will have no carrier bearings on it. You have to order those separately (Just buy a rear-end rebuilding kit). I paid $90 for mine online. I went to a friend's shop who has a hydraulic press and he pressed on the new bearings for me.

Since I was using my original 3:55 gears, I didn't have to pull the pinion gear, so that meant my only variable would be backlash (Pinion depth and shim remained untouched at factory setting)...and I would adjust backlash with the carrier side shim thickness.

In my video, the mechanic used a special shim knocker tool to friction fit his final shim choices into the diff housing. I made a steel shim knocker tool with some steel stock I had, my Roto-Zip, and a bench grinder. Without a knocker tool, you will likely break your shims.

First I raised the car with twin hydraulic jacks, then put in back-up jackstands, and chocked the front wheels so it would bit roll. Safety first - my car is lowered, so falling off the jacks would likely mean my death. Please don't trust your life to Chinese built hydraulic floor jacks only if doing this:



I completely removed my rear sway bar and dropped the pass. side panhard bar down to the floor. I noted my panhard bar was installed backwards by Modular Powerhouse. This is why I don't trust anyone else to work on my car. I'll save that rant for another thread. Grrrrrhhhhhh! You can see the sway bar and panhard bar would be in the way if not removed:



Next, I pulled the differential cover and let the fluid drain. Whew, stinky! My assistant Megan laughing at me after I pried the diff. cover and had a miniature Deepwater Horizon incident:





I then removed the bolts and support straps holding the drive-shaft to the pinion, but first I marked the orientation with a marking crayon. You want to re-install it in the same orientation to avoid vibration.





I removed the rear wheels and the two brake caliper mount bolts from each wheel, and I slid the calipers off, making sure the parking brake was off first. Air power and an impact wrench are your friends on all these bolts...lots of red LoK-Tite is present. I set the calipers on top of the drive shaft:



I then removed the center pin holding bolt off the stock carrier housing and slid the center pin out. I'm probably speaking Chinese if you haven't ever seen the guts of a diff before, but these pics should
help. The bolt I am referring to is at the 3:00 position on the carrier:



The bolt:



Once that bolt is out, you can remove that big one-inch diameter steel pin you see in the above picture which is in the middle of that S-Spring.

Then I pushed the axles in and slipped the C-Clips off with needle-nose pliers. I slipped the axles out partially.

C-clips:



Axles slipped out:

[DiMora]

Next, I hooked up my Harbor Freight dial indicator with magnetic base to check the factory gear backlash. It was .0105 Spec is .008 to .015 with .010-.012 preferred. I had read I should set my backlash spec with the True-Trac on the tighter side to minimize noise, but as a novice I was going to be excited just to get it close without too much hassle:

http://www.youtube.com/watch?v=oW5J67IfYmY&feature=player_embedded

http://www.youtube.com/watch?v=oW5J67IfYmY&feature=player_embedded

With factory backlash noted, I impacted the carrier bearing end caps off, then I took a BIG pry bar and started pulling the carrier housing out. There is a notch at about the 10:00 position you can use to get the left side shim out. You can see the dark area just INSIDE of the left side of the diff housing...just to the right of where there is residual rubber sealant. The bearing caps have arrows that MUST point to the outside, and the caps must go on the same sides from which they came:



The whole carrier will then fall out - be careful - it is heavy and slippery with all that gear oil. You could Brakleen it all before removal, but I didn't:



I cleaned out the differential housing with paper towels and removed the fill-plug:



I impacted the bolts off the ring gear and then used a synthetic mallet to knock the ring gear off the old carrier. It is a friction fit so you have to get kind of "Mel Gibson" with it:





Next, I installed the ring gear onto the True-Trac carrier housing. I ended up starting one bolt on the ring gear and then pushing the opposite side on in my vise with lots of cardboard in the jaws to keep from marring anything. Don't you hate it when you learn techniques after the fact? Well after struggling with that part, I ran across a technique on the net: put the ring gear in the oven at 300 degrees and the carrier housing in the freezer...wait 30 minutes...and they say it slips right on. Oh well. I got mine on with no damage nevertheless. If I was really smart I would have remembered putting Carmen's pulley in the oven when I had my M90. I put red Lok-Tite on the bolts and torqued them to 77 lb-ft:





Next, I set the True-Trac carrier in the diff housing along with new bearing races and I started shimming. I tried my original shims and immediately broke one while hammering on it with my homemade shim knocker tool. Waaay too tight- the True-Trac is evidently wider than my OEM carrier housing. Ford says to start with a .265 shim on the left. I did, and then shimmed the right side by hand until I had a tight friction-fit. I installed the carrier bearing caps and torqued them to 77 lb-ft and checked backlash. It was .0085 at three locations - right where I wanted to be.

Then I pulled the bearing caps off and added a .010 shim to the left and changed my shim stack
on the right to get an extra .005-.010 on the right. Pounded the last shim in on the right with my homemade tool. Bolted back up, torqued, and then I again triple-checked backlash at three different locations - again I was right at .0085:

http://www.youtube.com/watch?v=wRwdoSk7E8A&feature=player_embedded

http://www.youtube.com/watch?v=wRwdoSk7E8A&feature=player_embedded

I then put marking compound on the gears and checked my tooth pattern. I took pictures and compared them to the pics I was supplied in the how-to video, and also had the gentlemen that sold me the video give his opinion. Once I was confident my tooth pattern was fine, I buttoned it back up. Final pattern:





I had a problem getting the axle spacer installed. Per Eaton's instructions, after installing the carrier housing (True-Trac unit) you put the C clips back on the axle inner ends, then pull the axles outward, then slip in the spacer. Put the cover on and a big snap ring and you are done.

Well, my axle spacer wouldn't slip in- so I tapped on it with a metal rod and hammer. Bad idea. It wouldn't go in. It also wouldn't pull out. Crap. I thought I was screwed. Well, I was for a short while. I brainstormed...drill it and tap it? Nope...hardened steel...plus metal shavings in the unit made that a bad idea....weld a slide-hammer bolt onto it? Pull the whole rear end, admit defeat, and go to a machine shop?

Then I thought of another idea...I put a bolt on my slide hammer and made a 90 degree hook on the bolt and shaped it on my bench grinder... I then hooked my little contraption behind that spacer, and about 20 blows later it popped out. Not a mark on it or the True-Trac. Hardened steel. Whew!

Here is the spacer...I am holding it above where it goes inside the differential:



So why didn't the damn spacer slide in? I called Eaton and they said "Oh yeah, Ford changed their rear axle dimensions on the Mustang, and that spacer is too big...you need to take off .037" and it will fit".

Not trusting the guy on the phone, I decided to actually measure the distance myself. I used a 16mm socket and a .008 feeler gauge and had a friction fit between the axles. I put a micrometer on that socket / feeler combo and also mic-ed the spacer, and the spacer was .008" too wide. Off to my buddies' machine shop...I decided on shaving .007 off each side for a total of .014" off...giving me .006" slop which should allow for lubrication between the axle ends and spacer. We ground .007" off each side of the spacer on a surface grinder so as to avoid compromising the hardness of the spacer.

http://www.youtube.com/watch?v=qrajMPVUpYY&feature=player_embedded

http://www.youtube.com/watch?v=qrajMPVUpYY&feature=player_embedded

After grinding, it slipped right in. I then installed the cover and snap-ring.

I cleaned the OEM diff cover with some Brakleen and then used some Yamabond semi-drying gasket maker in lieu of the rebuild kits paper gasket to install the cover. I'll upgrade the cover to a racing girdle when I do Steeda Big Brakes. The cover bolts were torqued on to spec, and I gave it 5 hours to dry...then I filled it with Lucas non-synthetic 85W-140 gear oil (NO Friction modifier!), put PTFE plumbers putty on the fill plug and snugged it in. With a 3/8 drive extension and ratchet.

It took about 2 and 1/3 of these:



Brake calipers and wheels were re-installed and I was done.

Off to test drive...

Low speed corners no longer have that groan (my OEM diff and clutch packs were shot and making noise as described in a TSB).

Accelerating through a corner is now nice and smooth, and I don't hear any noise at all.

I took it in the highway and accelerated to 60 and decelerated...no whine noted.

I need to get the car on a very twisty road or a racetrack to really see what it can do...I might go to the Cherohala Skyway this week to wring it out...but initial impressions are that cornering feels more balanced and smooth with the True-Trac. I'll post an update in this thread when I have more time behind the wheel with it. So far, I am pleased.

[06RedfireGT]

Very nice write up.

Just go back and paste the video URL in there, not the embed code.

[DiMora]

Originally Posted by 06RedfireGT Very nice write up. Just go back and paste the video URL in there, not the embed code.

Fixed. I think. Is it working on your end now? Looks good on mine.

[06RedfireGT]

Yep. +reps

[king_Ahmet]

wow bro... Great post! I would never have the balls to do that myself... props...

[Redfire427]

Shane,

You are my hero. Another fantastic write-up. Great photography too. This is something I may tackle some day down the road. It will be great to have a source like this for some guidance. I will interested in reading about your long-term experience with this new piece of hardware.

Carmen

[stanglifemike]

Nice work bro!! Congrats!!

[brianm]

nice, this should go into a stickey without a dought.

[scottee]

Originally Posted by brianm nice, this should go into a stickey without a dought.

Agreed!

Very nice post! Thanks a ton! (The spacer info is extremely helpful)

Does Eaton sell/include this spacer with any of their kits or sell it individually?

Scott

[DiMora]

Originally Posted by scottee Agreed! Very nice post! Thanks a ton! (The spacer info is extremely helpful) Does Eaton sell/include this spacer with any of their kits or sell it individually? Scott

The spacer comes with the True-Trac, but I don't know if they will sell it individually.

Give them a call and ask:

800-328-3850
Eaton Auto division X# 379

[Anthony05GT]

Nice job. Gotta give you credit for jumping into that. Takes balls the first time and some guys (even techs) never do out of fear. Cute kid too.

[RetroGT2006]

I give you credit man, that is not an easy job!! Very nice write up! + reps