I'm in the middle of dropping in a T-2R into the racecar. It previously had an auburn, that I swapped out for a T2 before I started racing. I simply swapped the ring gear onto the "new" diff and dropped it in reusing the factory diff bearing shims, didn't even check the gear pattern. This has lasted me a few seasons and the gears look great.

I now bought a used T-2R, and am in the process of doing the same thing. I swapped out the ring gear (even tho it had a 3.42 on it already) to keep my ring/pinion 'matched'.

This one went into the rear end a little tighter than I remember the last one doing. Again, I just used just the thick factory shims. It still moves freely, and 'tinks' forward and back after a few thousands of movement. Since I'm not replacing the gears (especailly the pinion), how critical is it to find some gear marking compound (can't find any locally) and checking the pattern? Everything I read is about setting up a rear end with new gears, and I'm really not wanting to buy the whole setup to meaure.

Also, I don't remember what I did last time, but are you supposed to use loctite on the caps and the small small bolt on the diff? Ring gear, red of course. Caps, blue? I seem to remember reading you not wanting to use anything on that small bolt.

 

You really need a factory service manual
Back lash, pinion depth(with new gears) and pattern should always be checked. There is a backlash spec you want to shoot for but you can tighten it or loosen it depending on what your doing.
I have setup 300 ish rearends..

 

Setting it up properly is the difference between your gears lasting 30 miles, and 300,000 miles.

 

So basically, it doesn't matter if the exact same gears are used, gotcha.*

I do have a factory service manual, didn't look at it because I just don't have the dia indicatorl/mag base/shims/compound etc which I KNOW it will tell me to use. Guessing it says the backlash spec is ~.004-.010

That said, the pinion shouldn't need to be adjusted, right? If anything, only the diff bearing shims will need changed?

*edit to clarify. It shouldn't matter if they're used, I should still check the pattern and backlash

 

If you're not disturbing the pinion, then all you gotta do is make sure the backlash is OK.

Standard method of doing that is a dial indicator.

Spec is something like .006" - .012", .004" - .010" is plenty close enough. I like to leave em a little on the loose side, up in the .010" range or slightly beyond, especially for "heavy-duty" use; reason being, gears (and anything else made of metal) "grow" when they heat up, and while I don't like slop in my drive train, I like what happens when 2 moving parts attempt to occupy the same volume EVEN LESS.

The carrier SHOULD fit tight. I don't have a "case spreader" to bend the case out wider for installation, so I usually use a couple of C-clamps to compress the bearing races onto the cones to get it to fit. I like to see about .010" of preload on the carrier bearings if I can get it and still put the thing together.

As a gauge of distance, a business card is about .016", and a piece of copy paper is in the .0015 - .002" range. Those should give you a fair idea of how much backlash you should shoot for... about, most of a business card.

In case you can't tell, a certain amount of precision is ABSOLUTELY REQUIRED doing this; then beyond that, it's a bunch of "measure with micrometer, mark with chalk, cut with axe". Save the "precision" for where it REALLY MATTERS.

 

I forgot my father in law did gears in his mustang once and has the gauge. Should be able to borrow that and get a good reading on the backlash as you guys say. May even pull it back out and measure the shims and compare them to the shims from rear end the T2-R came out of since I didn't think to do that while I had them both out.

I'm still questioning if I even can do the pattern check. The install guide for Richmond Gears mentions "An accurate evaluation can not be obtained on a used set."

Thanks

 

Screw richmond they're just covering their own butts.

Put the gear marking compound on it, watch the pattern. If it's okay, check backlash, if it's okay continue on with your life.

And I find it interesting sofa likes to set his up loose. i've always heard the opposite, in racing applications you want it a little tigther so that there's less impact during launches or sudden applications of power. Too much slop and the gears work like impact hammers against each other. But honestly sofa, your way makes just as much if not more sense. Honestly I've gotten so fed up with distinguishing hot rodder superstition from reality at this point that nothing surprises me anymore. You just gotta take things on faith...

 

Something else to add. I picked up the dial indicator from the FIL the other day, and he mentioned that you want it one way (he thought tight) for drag racing and the other way (he thought looser) for roadracing, so you both may be right. It makes sense as you say for drag racing wanting less impact, and like sofa says looser for the heat generated for road racing.

Mine ended up being .005 for the racecar/T2-R, and .006 for the 4th gen rear(that the T2-R came out of)/T2. Patterns were ok, but not really really consistent, I'm guessing due to worn in gears. They were centered on the teeth side to side, so I called it good 'nuff.

Thanks

 

One race weekend down, no problems so far.

One more question tho. Since I upgraded to a T-2R, should I do anything to the rear spring rate to keep the car balanced? If so, which way do I go, soften or stiffen up the rear? Currently running 1000lb front/200lb rear.

 

I would listen to the car. If everything is working well I probably wouldn't touch the springs.

How do you like the T2R? I am putting one in a Dana.

 

The car felt good at the last race, but the three tracks (out of six) where I think it will make a big difference we won't race on for a while (June, Oct, next Jan).

 

You're still going to tune w/ swaybars after it's sprung. Too much bar = oversteer. (duh, duh, duh)

Since you're coming from a T2 and the T2R is a semi-aggressive pre-load friction pack on top of a more aggressive torsen spiral gearset, it may make a difference and you should provide updates. Hope I remembered all that correctly.

 

That spring combo is a nice starting point. Listen to your butt for sway bar changes.

I had a t2 in my old car, and a T2R in the current car. My setup is not yet optimized, and i have a bit different powerband that before, but I *like* the T2R a LOT. It takes a little time to get the balance at corner exit, as you can jump from push with rear grip to throttle looseness quickly, but still progressively. I can still spin the inside tire when i apply too much stupidity at once, but not nearly as easily as with the stock T2.