I have a 71 8.5 that has (I think, going from memory) a 2.56 r&p. I am putting a factory posi(recon'd by Monzaz) and a good used 3.08(also from Monzaz) in it. My question is on the pinion depth. Is there a starting drop dimension from carrier c/l to start with, or would it be easier(or better?) to use the pinion shim from the 2.56 pinion and go from there? Or maybe take a drop dim to the 2.56 pinion and then match the drop to the 3.08 pinion? I plan on using the old pinion brg(with id enlarged for slip-fit) to set-up the 3.08 pinion with. Thanks for any help...
Trial and error. I am about as inexperienced as you get with experience, having now set up two rear gear sets in a GM 8.5". One new richmond 3.70 set and a second used 3.08 set. I just used the pattern grease and made changes accordingly. I started with the shim that came with the original gear set to the axle. The 3.70's were completely silent in all forms of operations. The 3.08's whine just a little on hard de-accel, but are quiet otherwise.
STart with the original bearing under the 3.08 I sold you IF it is on there. Bolt t all together and see where you are. YOU MUST keep the backlash in check everytime you do a pattern check. ALSO you must have the carrier bearing preload snug enough that you CAN NOT pull the carrier out with a hand tug. You must have to pry the carrier out for a proper fit. NOT TOO tight either that you have to hammer the crap out off the shims to drive them in and metal starts getting ripped from the case and or shim. THIS is one of those areas that EXPERIENCE is KING. NOT to say you can not do it just use logical knowledge IF it seems wrong it probably is. :3gears: :3gears: :3gears: :3gears: :3gears:
POST pictures each time you do a swap and tell us the shim being used and your backlash. Use the marking compound on about 7-10 teeth coast and drive side and sin the carrier around completely 4-5 time. MAke sure you snug up the pinion nut with out the crush sleeve so you get a good drag that will help the pattern come out better too. LETS SET_UP A REAR!:beer
Yes, I posted pattern pictures a half dozen times on my first time setting up gears. After the picture is taken, go into a picture editting software (I just used the basic Microsoft picture editor with Vista) and adjust the contrast and saturation to "highlight" the pattern to make it easier to see.
I won't be able to get to it until at least this weekend, if even then. Just getting together a game plan before I start and hope I have all my bases covered. BUT, I will try to post(with pics) when I do start putting it together. Hopefully sooner, rather than later. I've had the parts for almost a year now, but I need to quit procrastinating and just do it. If anyone else has anything else to add, keep the ideas and encouragements coming. I will definitely need them. Everything that I got from you, Jim, is pretty much still boxed up, so I will have to check and see if there still is an old pinion brg on the 3.08 pinion you sent me. I do remember that you installed the carrier brgs already, though. Thank you for your help, Jim, and everyone else's as well.
OK. Back to the top. FINALLY getting around to this. Here's what I've got. Backlash is .008 . Carrier bearing shim ring gear side is .248 Other carrier bearing shim is .242 The carrier bearing shims were the shims that were with the original open carrier. The pinion shim and bearing are the ones that came with the 3.08 ring and pinion that I got from monzaz.
.020 maybe little more that will tighten the backlash a good bit too. Brian or Jim could tell you better. I like backlash at .004 to .006 myself , to allow for wear but up to .012 is fine for a cruiser will run cooler and quieter with mor lash
Update... Added .020 to pinion brg(had .034, now .054) Backlash is .006-.007 Carrier bearing shim ring gear side is .235 Other carrier bearing shim is .255 I think I need to take some shim away from the pinion. Looks too deep to me. What do you guys think? edit...one more difference...new pinion bearing in now, old one trashed getting it off to add the extra .020 shim.
Why would you add .020 to .034 that is .054??? That is WAY too much, anything over .040 in a 8.5 you have to start asking questions. if you had a .034 in there... That pattern is almost dead on. so .036 .037 .038 are the most popular 10 bolt 8.5 factory shims. I would go with .036- .038 shim and get that backlash to .008-.010 for USED gears. Have fun. Jim J D
Thank you for looking at this. Nice talking to you earlier. I will try .036-.038(whatever combination of shims that will give me something in that range) and adjust the carrier brg shims accordingly to get the backlash where you recommend. Won't be able to get to it tonight or tomorrow, but will try to do something Weds night and I will post pics of results Weds night sometime. Thanks again.
You don't need to jump that much in shim selection. You'd be surprised much .004" difference can make. Try a .038",reset the backlash,and see what you get.
Be also prepared for the pattern to slide down the face...If it goes too far you may have to go back to the .034...lol. I know it sounds weird ...BUT this is the only way to determine what the gear face is looking for. Your dealing with used gears and your trying to find where it was riding to get the best set up you can. JIm
Update #3... Pulled inner pinion bearing off of original 2.56 pinion gear. It had a .041 shim under it. So... I installed the .041 shim on the 3.08 pinion and put it all back together. Backlash is .010. Carrier bearing shim ring gear side is .242 Other carrier bearing shim is .248 Basically everything set as the original 2.56 r&p except now it's the 3.08 r&p. Here's the pics...whadya think now?
OK. Just as a quick refresher if this is the final setup before finish assembly. I know the backlash on used gears should be about .010. As for the pre-load on final assembly with crush sleeve and seal installed, what should the pre-load be both without and with the carrier installed? Also, at about around what point(torque foot/lbs) does the crush sleeve start to collapse? And one last question, I can't seem to find the bolts that hold the brake backing plate and axle bearing/seal on. What size and length will I need, and I'm assuming the bolts and nuts are both flanged? Lock washers or lock nuts? Or can someone post a picture of said nut/bolt combo which may help me find mine that I might just be overlooking them. Thanks to everyone for your help!
So I'm assuming that under load, the pinion will go deeper into the ring gear? or vice versa, whichever the case may be. Is that why you're suggesting to get the pattern out farther? Not questioning to be difficult, just trying to learn. I will put the .038 in and post some pics later. I really appreciate all the help.
