Rebuilt my Rear End and installed TrueTrac

[Bad70sbchevy]

Hey everybody, just wanted to show off what I've been working on these past two weekends. School has been keeping me busy from doing too much with my truck, but I got an "excuse" to go work on it about three weeks ago when this happened. I was doing an italian tuneup on the truck doing a 1-2 shift at 6000rpm when I heard a loud bang, the kind that makes you sick in the stomach. Anyways pulled the truck over, didn't see any fluids leaking on the asphalt but I limped her back to the house. Sure enough when I pulled the differential cover a tooth came out. From what it looks like, please feel free to chime in, that a tooth must have broke on the ring gear (its the stock 3.07s) and jammed the gears, thus breaking the bearing caps completely pulling apart the bottom grade 8 bolts in half and bending the driver side bearing cap. Its never good when some of the gear oil looks like never-cease from all the ground metal.

[Bad70sbchevy]

Anyways knocked out all the races which came out fine except for the wheel bearings, which I ended up persuading them out with hitting them with a long steel pipe running through the axle housing. I bought the Richmond Mega kit and replaced all the bearings and seals. Since the bearing cap was bent on the driver side I had to buy a replacement bearing cap from Mark Williams. Luckily I have access to the student machine shop at UF so I got to mill the caps down myself. By the way I highly recommend these caps. I attached a comparison between them and the stock ones.

[Stepside Jim]

I know nothing about the Mark Williams replacement caps but most anything has got to be better than the original caps.

I recently rebuilt my 8.5 Gm axle in my 57, first thing I noticed was the weak looking caps. I like your caps but I at least ordered a Perfect launch cover that will provide some strength as it has the bolts that will apply pressure to the caps to keep them from moving as yours did.

I have to ponder.....did the tooth break, then got wedged and broke the bolt, or did the bolt break allowing the ring and pinion to flex thous breaking the tooth?

Jim

[Bad70sbchevy]

For mocking the pinion gear for shimming I took the two old pinion bearings and ground the inside of them so they fit freely on the new one. By the way, an air hammer works great for pulling the old bearing off the pinion if you don't have access to a bearing puller. Also freezing the bearing races make it a lot easier to install.

As far as prepping the carrier, if you drop the ring gear in water and get it hot enough just before it goes to boiling before pulling it out, it will drop right on the carrier. As far as the carrier bearings go, if you heat them on a grill or oven set at 200F for ten minutes, you can pull them off and tap them in using the old carrier bearings and a punch once they get past the lip on them (sorry for not having pictures). By the way I used an air hammer again to "pull" the bearings off the old carrier. You can tighten down the ring gear bolts, but its better to torque the bolts down to spec after everything installed since all you have to do is place the vehicle in park (or set the emergency brake for manual trannys) to hold the carrier as you tighten them down.

As far as getting the pattern right, I just used the richmond instructions to compare the pattern too and set the backlash to what they recommend. To get a real good pattern, put down a lot of the yellow marking compound and when rotating the carrier put some resistance on the ring gear and rotate in both directions. You just have to tighten the bearing caps down, but you don't have to tighten them down to spec just yet. You'll do this during final assembly. As you can see here I set mine where the drive side pattern (first picture) is to the middle/slightly inside and the coast to the inside (second picture). Having the drive side slightly to the inside is better for street/strip applications as what this truck is intended for. By the way my backlash is set to 0.008".

[Bad70sbchevy]

Yes Jim, those factory cast bearing caps are real weak. I really like the cover girdles and I'll probably get one if this truck starts seeing more track time, but I figure between the replacement cap and the stud kit it shouldn't budge right now. I've been pondering that myself which broke first as well, I just suspected it was the tooth since it was the original gears.

[Bad70sbchevy]

Once I got the pinion shimmed for the right pattern and shimmed the carrier for the right amount of backlash, I pulled everything out. I went ahead and got the inner bearing pressed on, but the outer bearing I went ahead and sanded the inner race on the pinion gear where it sits so that the outer bearing just starts to slide in (but not all the way). Then I took a wire wheel and hit the splines on the pinion gear so that the old yoke can slide on just enough so that the pinion bolt can thread on. Once I did this I put the pinion in the freezer and left the outer bearing at room temperature. While I let the pinion chill over night, I went ahead and pulled the wheel bearings I had stored in the freezer and knocked them in using the old wheel bearing to drive it in, then installing the wheel seals after that using a block of wood making sure they were driven in straight.

Then I put the outer pinion bearing into its race and then knocked the pinion seal in to keep the outer bearing from falling out, once again driving it in using a block of wood. Once I did that I pulled the pinion out and installed it. If all goes well the pinion should just slide right through the outer bearing. Make sure to install the crush sleeve at this point. Make sure to go ahead and put some thread locker on at this point. I used an impact wrench to snug the bolt down just to the point where there is no play in the pinion. My impact wrench did not have enough to drive the nut all the way in so I had to clamp the yoke with a pipe wrench and wedge it against the concrete floor and then put my 1/2" drive on the nut and put a cheater bar on it sliding it between the control arm and the wheel well. Basically you have to tighten it down till it requires 16-17 in-lb. to rotate it (for a 12 bolt truck). I didn't have a dial type torque wrench that does it so I balanced a 2.5lb weight on the end of a wrench to figure out the torque. (figured out the distance I had to balance the weight from the center of the wrench that corresponded to the required torque). Once I got it right I attached the drive shaft and proceeded to install the carrier, tightened down the studs (I used the Moser stud kit which uses ARP fasteners) to the specified torque, and then put the truck in park to torque down the ring gear. Finally I checked the pattern and backlash once again, put RTV on the cover and screwed it down. Only have to wait 1.5hrs before it was ready to pour gear oil in it.

[Bad70sbchevy]

As far as break in goes for 3.73s and up, I drove the truck for 10 miles and then let it cool for 30 minutes. Do this three times and then its ready to go. The differential does get hot but its normal. After 500 miles I'm going to change the fluid and put the good stuff in it. A lot of people complain about the noise from Richmond gears, but I didn't hear them at all unless you listen hard for them. The TrueTrac worked really well and it felt like I still had the open rear end in it until I got on it and there were two black streaks. I highly recommend it.

[Houston Ben]

Hey Bad70, I am in the middle of a true trac install and have a question for you. With the tires off do your axles move in and out approximately 1/8"? Looking at the cylinder that goes between the axles, mine seems to be too thin creating the "play" on the axles. I also had a squealing/screeching noise at first but not anymore, looks like you didn't have that problem. I took my diff cover back off tonight and there was nothing wrong, no shavings or anything. Any thought would be appreciated.

[Bad70sbchevy]

I do have that 1/8" play as well, I think that is just a typical tolerance for it. As far as the squealing noise, I'm thinking its either something in the pinion bearings or the wheel bearings, because if it was the gears you would hear more of a whining/racheting noise. Another thing it might be is the carrier shims might be too big, causing the carrier to be too tight against the shims. For mine I could not use the factory shims with the truetrac because it was too tight and the truetrac just would not fit with both in. Also the backlash would not have been correct as well. I think this is caused from the Truetrac being a hair wider than the factory differential.

[Houston Ben]

Ahhhhhh, got ya! Disregard my other post on mine, u just answered it! Thanks for your help man!

[Bad70sbchevy]

No problem, your welcome.

[Ironangel]

Well done! You encourage me to tackle my 3:08 12-bolt single spinner and drop in a Posi unit with a 4:11 ring and pinon gear...I've been researching and educating myself...Fear of the unknown is the biggest hurtle it seems...

[Bad70sbchevy]

Thank Micheal, thats exactly what I did when I did mine. Spent a week looking at a bunch of online articles and what others did before I touched mine. Its not a bad job at all as long as you don't get in a hurry and spend some extra time on mock up to get things right.

[68post]

I'd like some info on the bearing cap installation. It is my understanding that they are to be align-bored after installation. I see your found the correct diameter by milling the cap face only , or is this the recommended procedure from the mfgr. ?

Thanks, Tim

[Bad70sbchevy]

Yes, this is the procedure suggested by the manufacturer. All you have to do is mount the bearing cab as is, take the current diameter, then subtract that diameter by the desired diameter (which is 3.062" I believe, it in the included instructions) and that is the distance you need to mill off the end.

Alignment-bore is not needed since the cap does have a very small amount of play to move up and down relative to the floor, thus when you tighten it down on the carrier race, it will center itself thus the only thing that needs to match up is the "depth" of the circle center of the new bearing cap so you create a smooth transition from the housing to the bearing cap on that inside face.

Also note that this is just a clamping face to hold the carrier race, thus a very high tolerance is not needed like a journal bearing, but I still say take as many measurements as you can to get it to close as right as possible.

[68post]

Thanks, I didn't know it could be so easy and will probably need a couple/few of these in the future.