I'm installing a new posi unit with used 3.42 gears and new bearings in a 72 8.5" 10 bolt. I have the pinion bearing preload drag set at 16 inch lbs. Once I shim the side bearings on the posi carrier and get a correct pattern, how much should the preload drag increase on the pinion? I read about an additional 3 inch lbs. I want to make sure I preload the side bearings correctly. Thanks
I'm at 16 inch lbs with just the pinion installed and 20 inch lbs with the carrier bolted down. Carrier side shims were snug getting them in. I then added a .005" carrier side bearing shim to one side and the drag jumped to 25 inch lbs and my backlash went from .006" to .002".
They don't measure it that way, when you set the carrier up working towards you proper pattern and backlash, you need to pry the carrier side to side to get olsy measurement......you will want .008 preload on the carrier bearings......so if you have the pattern and backlash you want....say you have a side to side measure of .004 you will need to increase a total of .012, but by putting .006 on each side to not change the pattern and backlash. It might be easier to set preload first, then move shins side to side to get backlash.....just remember whatever you take from one side it has to go into the other to keep preload. Depending on your pattern you might have to adjust the shim under the rear pinion bearing which will require tearing it down and resetting preload. New bearing specs 15 to 20 inch pounds of rotating torque......I like to go on the mid to upper on new bearings cause they will loosen up some
Thanks. With backlash at .006", my pattern on the drive and coast side are both a little to the toe side from center. Not by much though. If i increase the backlash a little it should center, correct?
This is the first pattern. I'm at work now and didnt take any other pics. I wonder if I need to shim the pinion up a little from these pics. Started out with .033" on the pinion.
Those are bad pictures, sorry. I know what a correct new gear pattern should look like, but I'm not sure about used yet. Need to do some research.
Are you sure that you have the bearing race seated all the way into the housing? You do NOT need a crush sleeve during mock-up. Once you feel some drag,you are good to continue with the mock-up. You just want to make sure the race is seated all the way,and the bearing is seated on the pinion,so you don’t get a false reading. A used pattern can be a little more finicky to get it where it was before,and that’s if it was correct before.
Man it's hard to get a good pattern on these used gears. Pinion now shimmed to .041", backlash set at .009". Alot of contact on the coast side but not much on the drive side. Pinion was shimmed to .037" in its original housing. I'm just showing updates in progress is all.
Where’s Jim M when you need him lol. Used gears don’t pattern well. Backlash seems a little heavy. What’s the spec?
Ok - first off...you do not need to worry so much about all these pre-loads and torques etc. Do not use the crush sleeve and do not have a seal...they will just be in the way. What you need to do when your sending us pictures is tell us what pinion shim your using and the backlash of the ring to pinion. Pre-load on the pinion bearings just snug it up so it has a nice swish sound do not want to here roller bearings rattling around and you do not want the pinion so tight it is tough to spin the carrier in the housing by hand forward and reverse. So from the pictures you supplied it looks like the drive side (convex side ) needs more backlash... the coast side does look like it is getting a good swipe from top to bottom. used gears will always take more backlash to see what is going on. An 8.5 can be from .033 - .041 on normal set-ups. .038 is a very very common shim for 8.5 The carrier is critical to get snug ...you can not (CANNOT ) have the carrier loose in the saddles and be sure the carrier is always SEATED in the saddles by installing the caps ...you do not need to torque the caps just install them... So IF you can pull the carrier in and out by grabbing the ring and pulling, THAT is not tight enough. YOU have to pry the carrier in and out each time. SORRY if this is an inconvenence BUT if you want the changes to actual show you how your doing this is critical. ONCE you have the correct shims left and right all you need to do is add and subtract equal from each side to change your backlash. This should help you clean up that pattern ... hopefully Remember we need the pinion shim ... and the backlash always with the pictures. Thanks, Jim J D
Thanks. I put the shim and backlash info in the comments above. Pinion shimmed .041", backlash set at .009". I read that specs are .006 to .010 on backlash. Am I ok to go above .010 on backlash with a used gear set? Thanks for the ingo guys.
Change that shim to .038 and see what it looks like. with .010...Try to get that hard drive side toe hit more to the center of the gear...It is biting too hard in the toe. Jim J D
I do not know why this is so wacky unless the drive side has been compromise in its life and got a funny wear pattern from a loose pinion nuts or carrier bearing etc. Pictured are some of the concerns. Green coast side (not so bad you can see the swipe from top to bottom and left to right in the close up picture....the other one it is way too high on the coast side gear tooth. ) (toe to heel ) red drive side (not so great)
Just remember most used gears do not tell how good they are till you get them in and try to pattern them up. Sometimes it is a pot luck. Some stuff you can see right away...others are slight angle wear and hard to see with the naked eye till you start patterning it up. Jim
It will sing with the drive pattern that is on it now. Try a .036-.038 pinion shim,like Jim suggested,and the .010 backlash. Post pictures of the coast and drive when you do.
I'm not as familiar with rear ends as Jim or brian, but I think they will agree the specs for backlash and pinion shims are general area to aim towards. The preload specs on the bearing are needed for sure.......but if you have to go outside the general area to get the correct pattern then that is what needs done. The pattern is showing you exactly what is going on.
