TruTrac setup

Hi all,

Looking at (finally) installing my TrueTrac high preload LSD in my DD. I'm changing to a 3.73 gear ratio from the 3.31 that are in the car now.

Looking for anyone else's experience setting one up.

1. Did you measure pinion depth?
2. If you did, what tool did you use?
3. When installing your TT, did you swap gears?
4. Did you have to adjust your shims or did you get lucky and the factory shims were bang on?
5. Did you use a crush sleeve, or did you go with shims on the pinion?
6. Who did you get your install kit from (bearings, shims, etc.).

thanks!

You will want to play with the shims to get the pinion depth right and the backlash right. Fortunately, the greenbook has a revised setup for the pinion...the factory shim between the bearing and gear is removed, that thickness of shim goes between the race and housing on the inner bearing.

For the carrier, get a spare set of bearings, open them up a tiny bit with a die grinder to use as setup bearings so you can easily reshim, adjust your backlash that way and make sure the contact pattern is good. I don't recall my wagon or the 140 having a crush sleeve.

I do have a how-to thread on here that has part numbers in it for the install kit I used, all from Summit.

In my case, no I didn't swap gears though.

I've always done ratio changes via replacing the housing with one that already has the desired ratio.

Installed a number of limited slips in Volvo rear ends. Never needed to change a shim.

They drive so much better with a TrueTrac.

JohnLane said:

I've always done ratio changes via replacing the housing with one that already has the desired ratio.

Installed a number of limited slips in Volvo rear ends. Never needed to change a shim.

They drive so much better with a TrueTrac.

Click to expand...

This. BTDT several times now on DANA and GM rearends..... if you can avoid the pinion remove/replace by purchase of a complete rearend with the desired R&P installed, you will be HOURS ahead. The process of pinion setup is iterative.... there is no single set of measures and X marks the spot. It is done sans crush sleeve and you can use a "setup bearing" at the nose, but you will never get the pinion depth right until you read the pattern.

I just went thru this on my DD to convert to a 4.10 ratio.... bought a 95 NA rearend "axle to axle" from the local Pullapart, and then the only challenge is centering your TruTrac with carrier bearings & shims so you get proper preload and backlash. This again is an iterative process, as each time you must use a bearing puller to change shims. I think there were some slick OEM tools from DANA that adjusted the shim thickness but you won't find a set of those.

Find a 3.73 rear to start with and save yourself hours/days of toil.

When we did it we went from 3.73 to 4.10 in a 1031. 4 new bearings. Swapped the pinion shim coming out of the housing onto the 4.10 pinion, almost 100% of the time it's dead on as the shim is for variances in the housing. Used a crush sleeve out of an older GM 7.5/7.625 rr end. PN on the sleeve 9785792. Doesn't fit perfectly but it works correctly. Side shims were good. A LOT of race miles later still perfect. Drives awesome.

Beware of backwards pinion depth instructions. I have seen several that give the wrong direction.

If the pattern is too far out on the ring gear, you move the pinion toward the outside (remove shim between the pinion and the large bearing).
If the pattern is too close to the center of the crown/ring gear, add shim to push the pinion toward the center of the ring gear.
It’s all about the curve of the hypoid teeth. The pattern moves opposite of the pinion change.
(I typed it wrong just now and had to edit)

Also, the drive side is the small face that is more perpendicular to the mounting surface on the ring gear. Both are important, but the coast side is easier to read, but less important.
I use prussian blue if possible. I like it better than the yellow indicator.

JohnLane said:

I've always done ratio changes via replacing the housing with one that already has the desired ratio.

Installed a number of limited slips in Volvo rear ends. Never needed to change a shim.

They drive so much better with a TrueTrac.

Click to expand...

+1 same.

Truetrack itself swaps over easily.

To replace the carrier bearings I did some precision angle grinder work to weaken the inner bearing race. Just keep removing metal on one side and the race snaps. used the same shims, fresh Timken bearings. Lash between ring-pinion was back to middle-tight end of spec (was on the large side, but within spec). Those carrier bearings looked quite abused too. Wheel bearings and seals were fine, just some fresh grease and they were good to go.
So far so good. Changed the oil after about 6K miles. Some noise from the rear axle area but i suspect its a worn U-joint coupled with bad adjustment of diff nose angle..

For the rest, me happy. Its annoying now to drive modern cars with traction control now, some form of limited slip is so much better since it doesn't cut power (and yes I know plate type is better - we have that in the E30).

I'm about to do this with a rear axle I have. It has a 3.73 gears in it already and I was going to replace all the bearings and seals.

Is it worth the effort to replace the wheels bearings and seals or just slide the axles back in and reuse them?

probably not unless they look bad. I've never seen em look bad (though I'm sure it's possible)

Yeah I know it had a leaky pinion seal but the the axles looked fine.

Reuse your bearings, especially your carrier bearings. Otherwise you will need to set backlas and preload, which is great unless you need to have a shop do it for you, and that is always very expensive.

My biggest issue with axle bearings is usually the seal, not the bearing. I've had hit or miss luck getting them off so I just cut them and throw new bearings on when it's time for a seal.

Harlard said:

Reuse your bearings, especially your carrier bearings. Otherwise you will need to set backlas and preload, which is great unless you need to have a shop do it for you, and that is always very expensive.

Click to expand...

This is incorrect. Re-use the shims. The bearings are all identical.
(Unless you got wrong ones, no-name ones, your junk is worn out, whatever)

mikep said:

This is incorrect. Re-use the shims. The bearings are all identical.
(Unless you got wrong ones, no-name ones, your junk is worn out, whatever)

Click to expand...

my man. I called mike when I was setting one up, he talked me off the cliff...


what helped me was making a set of test bearings for the carrier so I could play with the shims ahead of time. For whatever reason, the shims that were on the old rear end weren't quite enough and I ended up playing with it (TWSS) for a while.

Harlard said:

Reuse your bearings, especially your carrier bearings. Otherwise you will need to set backlas and preload, which is great unless you need to have a shop do it for you, and that is always very expensive.

Click to expand...

Every limited slip I have put in a Volvo rear end.... Clutch type, TrueTrac, ZF.... All of them. New carrier bearings with shims in same position as original. I always check gear pattern... All were perfect.

The few pinion bearings I have done all turned out fine with just doing bearings...

The rear ends that creep me out use crush sleeves.

Ahhhhh. That's what all axle shops told me. Good to know it's not actually the case.

On the crush sleeve topic, I put a Turbo 1031 in my ****pile to have some peace of mind.

Bearings, as long as they are from a legit manufacturer, have some pretty damn tight tolerances to design spec so they should be swappable on the same carrier. I did have to reshim installing the TT in my wagon and the 140. The shop that swapped a new gearset and the TT in the 140 used the original shims. Pinion was way deep, preload was WAY high, bearings were trashed in the process. I have the OE setup tool for the diff which has adjuster sleeves, really helps, but a set of testfit bearings with the ID just enough to slip onto the carrier or pinion works just as well.

For my install I went with the cheap route. $70 complete JY rear end 3.73 ratio G80 and $500 TT trutrac from Summit. Had a hard time sourcing a shim kit for the Volvo Dana 30 so I opted to reuse everything. Backlash was within spec and gear mesh was identical to G80 after install. Re-used bearings and put the spacers in the same location as the G80. Bearing preload was a hair tighter but I could still install the unit without the use of a case spreader. Cut my 44 tooth tone ring down to 12 and welded it on the case. Spaced the speedo pickup and called it a day. 3,000 miles later it has been a lot of fun with the wet weather and this car's second M46. I did not mess with the pinion as that is a can of worms...

Only issue I can say is the high preload version is set up TIGHT. I cannot spin the wheels in opposite directions on jack stands by hand. I posted a video of this awhile back and had concerns of long term use but it has been fine so far. Only complaint while driving is that on a slight bend in the road, say 75 mph on a curve in the highway, the car wants to 'push' forward and it takes more steering effort to direct the car off its straight line than with an open diff. It also returns to center with more force than before. I have an international scout with a TT unit and it is not set up this 'tight.'

Other than that enjoy your new found traction!

Funny yours changed the car that much Wil. I definitely notice the tight preload with the 588 being a little tighter than the 410 it seems but it really doesn't push at all. I will say, swapping to Ben's camber plates and -1*, it changed the entire car, making turn-in buttery smooth. My only issue is I don't have enough tire for 1st anymore, or part of second. lol

One “gotcha” on the tru trac, there are two different diameter holes for the ring gear. The Volvo ring gear uses the smaller diameter holes. Use red loctite on the bolts. Harlard had some... issues... from the shop that set the diff up the first time. If your car makes enough torque, the ring gear will rotate back and forth on the diff when using the large holes.