NullHead

So I'm rebuilding mt 7.5" Torsen Zexel 10 bolt. Got it in a trade, and pretty much slapped the whole rear in and didn't check it at all before running it (Bad idea, I know). Turns out, the main caps were loose and there was a bad carrier bearing.

So I have the rear out, and I'm in the middle of a fuel pump/rear rebuild. So far I've put new carrier bearings on it, and adjusted my backlash from nothing after the carrier bearings, to .006 after I dropped .010 from each side. So now that I feel that my backlash is in spec (Right? 6-12 is what I was going for), I painted the gear to check that and here's what I have:




Orientation is that I'm setting "above" the differential. I'm really not sure how to proceed from here .. I've read and read and read up on how to do this, but where I'm having trouble is "where to go from here". I get how to adjust the pinion, I get how to adjust backlash, but it's the "now what" that's getting me.

So .. I'm guessing my backlash should move a tad towards the pinion, and the pinion should move a tad outwards (smaller shim). So far all I have done is change my carrier bearings, hoping for an easy swap with my backlash remaining unchanged ... this was not the case. So my pinion bearings are okay and still original, but I have a full rebuild kit at my disposal. I can easily change pinion bearings/shims. That's not an issue. I'm more so just trying to figure out where to go from here. This is what I have .... ok cool, now what?

big gear head

If I understand you correctly the gears were swapped and the Torsen was added in this rear end and the pinion depth and backlash were not checked.

This is going to be very difficult. First, you have a used gear, which is very hard to read. Second, this gear has been run with a bad set up, which is going to cause even more problems with the pattern.

From what I can see it looks like the pinion is not deep enough. What is the current shim thickness on the pinion? Do you have the bearing preload set correctly? It's important to have the bearing preload set when checking the pattern.

Here is my advice. If you can get this somewhere close then that's great. I would be saving some money for a new gear if I were you. This one might work out fine, and if it does then that's great, but there is a good chance that it's too late for this gear. Hopefully it will run quiet and give you good service.

NullHead

Thanks for the response, I'm getting the same feeling. This setup might not be destined for use.

So, full story as I know it. I had an entire rear housing that I traded for this entire rear housing that had this Torsen in it. I was told the rear end was good, and that the previous owner was using it when he pulled it to swap to a 9 inch. So I'm the second guy to have this after the original owner as far as I know.

That being said, I ran the rear without going through it when I initially got it. I just swapped the entire housing into my car, filled it up and ran with it. It was noisy. So far my findings are that I had one known bad carrier bearing, because the cage on the bearing was bent and the outer race was pitted. From my findings, someone some time swapped carrier bearings already, but did a poor install of the bearings themselves.

So now here I am, I pressed on new carrier bearings, reassembled and found that the carrier was VERY tight in the housing. I began checking backlash, and found that it was so tight, I couldn't even read any noticeable backlash. So, I pull the carrier again, pull the pinion out and inspect the bearings. The pinion seems OK, so I re-install the pinion, and torque it only to the point of no play and I can spin the pinion about one full turn "coasting" meaning, I just give it a spin and it goes one full revolution and stops (I read to do that in an online tutorial .. don't know if that's correct or not).

It doesn't need to be bullet proof, but when I ran the rear end before I took it apart, it sounded like something was going to break. I'm OK with a little gear noise, as long as it holds up to some moderate driving. My car isn't a drag racer by any stretch of the imagination.

So the pinion shim, I really have no idea. I was trying to get away with just slapping carrier bearings in it and calling it a day. So I didn't remove the pinion bearing to get the shim out. The carrier I was able to get to spin more freely by removing .010" from each side of the carrier shims, giving me a backlash of .006 when I rock the gear back and forth.

So from what I understand about what I have done, I have .006" backlash, and my pinion is unchanged. Using the original shims for the carrier resulted in it being so tight I couldn't spin the pinion by hand.

I hope that helps shed some light on what's going on here. Again, I'm less than a novice at best, I really only know enough to be dangerous. I've read countless online tutorials on this and I'm giving it a shot. I have a rebuild set with new bearings for my carrier and pinion (already used the carrier bearings and shims). I can go ahead and change my pinion depth. Would it help if I shifted the carrier closer to the pinion by .005? Moving .005 from one side of the carrier shims to the other? Maybe .010?

big gear head

With used bearings I guess it's not too far off for the pinion to spin slightly, but I don't like it. If this was a new build with new bearings then that would be way off. The differential should be tight enough that you can not pull it out by hand with new bearings. If you can pull it out then it's not tight enough. If it had used bearings then it should still be tight, but not quite as much. Backlash on a used gear should be around .009 to .011. You will probably never get a decent looking pattern on this gear, and it will probably make some noise.

NullHead

So it has new carrier bearings. And I can put new pinion bearings in if that would make things easier to make this pattern closer to "good".

So my concern is that I don't know if the pattern was ever good. To pull the carrier from the housing took a considerable amount of effort and prying with my pry bar on the ring gear bolts.

So you're saying that basically with a used gear like this, there's almost no way to get a good looking pattern unless I replace everything - gears and bearings?

big gear head

Used gears can be set up, but I think these have been run with a bad set up and are probably not ever going to have a good pattern again. Changing the pinion bearings isn't going to help with the pattern. Changing the pinion shim might help.

NullHead

So, I know you said it, but I'm becoming more convinced that my gears are bad, and here's why.

Originally after swapping out my carrier bearings, I put it back together with the stock carrier shims and felt no appreciable backlash. Measured absolutely none, and somewhat freaked. I pulled it apart, assembled my shim pack from Richmond with each pack being .010 smaller per side for a total of .020 total I freed up the carrier. This got my .006 backlash, and I could now spin the pinon flange by hand and there doesn't feel to be any binding.

Now that I'm all sorts of confused about my pattern, I play with my shim packs a little more, and gain absolutely no ground, so I reinstall my original carrier shims, and holy smokes, my pattern goes back to an area that looks like it's salvageable .... but there's a catch. I cleaned the gear and marked a different section from last time. So now that these original shims are back in, the same ones that made the carrier feel as if it was completely bound tight, spins freely not even a full revolution then binds up, as if something is bent. So I install my dial indicator on the face opposite of the teeth, on the area that is flat against the carrier and the bolts hold it. I measure .006 runout on this bad boy when I spin the carrier via pinion flange.

So ... warped gears, warped housing, something wrong with pinion. I'm just about sold that I need new gears. My only concern at this point is that if I put new gears on this carrier, that my housing or carrier its self it warped. Should I remove the pinion and ring gear and measure my carrier just shimmed/torqued down to the housing? I'm thinking at this point, my safest bet is to get a whole new setup. New housing (disc brakes!), order myself a new locker/posi from somewhere, and order up a fresh gear set of my choosing.

big gear head

.003 run out on the ring gear flange is usually considered max. If you have .006 then something is off. Remove the ring gear and measure the run out on the ring gear flange without the gear installed. If it exceeds .003 then consider buying another differential.

NullHead

I'll check that tomorrow evening. How likely do you think it is that the housing is bent? I was talking to a guy at work and he said sometimes the axle tubes can bend or get shifted which might have been what caused the carrier bearing to go out in the first place, before the P.O. installed new bearings.

He said there is a checking fixture that they mount on the main caps that holds a rod that runs all the way through the differential . If the rod isn't centered in the tubes, they are considered bent. Think any of that is worth doing to a 10 bolt? I'm not looking to dump the cash on a 9" at this point .. this 10 bolt I was hoping would be decent enough to run with for the peanuts I paid for it.

So at this point, I have a questionable 7.5" Torsen 3.73 drum rear end, and the car's original 8.5" 2.73 open drum rear. The seals were leaky on the 8.5 rear, but the gears weren't noisy. I suppose I can reseal the old housing, get a new gear set, and use my Torsen differential in there ...

or are there cheaper options for a posi type effect? Seemed to me at the time that a Torsen diff was a pretty good option for the price and availability. I could always go salvage yard shopping for a posi out of a 4th gen ... Ideas?

big gear head

The only 8.5 rear end that was ever used in these cars was the Dana 44. If you have one of those then you shouldn't even be mesing with the 7.5 rear end.

A bent housng is't going to cause the problems that you are having. Your housing could be bent, but that would be a different problem.

NullHead

Oh okay I thought the 2.73 rears were 8.5 lol my mistake.

TxTtopZ

Yeah your on the heel of the ring gear. Def. could try less pinion shim. Before you do that, take the carrier out and set up the pinion turning torque. I believe 25 lb in. ?? For that one... Once you have that going right, then put back in the carrier and lightly torque the caps with your suspected shims in place... recheck pattern. You have the pics of the worn paint shown, but not any with the paint transfer. The transferred paint on the carrier shows more of whats up as that completes the ring gear picture. Also keep in mind you are not loading the carrier just by spinning the pinion and looking. Try putting some force going the opposite way on the carrier while spinning the pinion and this DOES impact the paint more and creates a clearer image of your set-up.

From the looks of it so far, the pinion depth is too shallow and needs to be shimmed less to bring the markings closer to the toe on the drive side and less carrier shim to push the carrier out on the coast side as those markings are too close to the toe.

This of course, is just judging by 2 seconds of looking at 2 pictures and probably has no useful information at all..

NullHead

Thanks TxTtopZ for the reply!

So I'm not sure if you have read through my enormously long detailed bibliography of my findings inside my lonely 10 bolt, but after careful examination, I discovered that the carrier is binding, and that the ring gear is warped.

Just tonight, I removed the ring gear only to find that when I measured the ring gear flange, that I still have the same .006 runout ... which means my carrier is junk.

I was hoping that this damage here wouldn't mean the end of the carrier, but apparently it does.

big gear head

Looks like that one has seen some abuse. It was probably in a rear end that had a major gear failure and that probably bent the ring gear flange.

TxTtopZ

Thats exactly what it looks like. I've seen worse than that tho. I would grab another carrier and start over. As for the mass info I missed, I was at work during lunch and only skimmed the post. Sorry.

Anyway, another carrier, new bearings and some shims should put you back in shape.
I would offer you my 10 bolt but it sold already.

NullHead

That's the plan as of now, find a new carrier, probably an eaton posi, and grab a new gear set and start over from scratch.

That being said, what are your guy's feelings about used posi units? I'm not into dropping $5-800 on a new carrier .. I'd love to find a used carrier around the internets or locally and run with that one.

Good thing I only had peanuts into this rear end, cause that would really rub me the wrong way if I spent good money on this thing.

big gear head

Usually the only used differentials that you are going to find for the 7.5 are the Auburn and the Eaton Governor Lock. I wouldn't give a dime for either one. The Eaton Posi was never offered in the 7.5 from GM, so finding a used one is probably going to be difficult. The Yukon Dura Grip is a little cheaper, but just as good. Contact Tom's Differentilas for Eaton Posi, US Gear and good installation kits, and Jim at www.jdrace.com for the Yukon Dura Grip, Yukon gears and good installation kits. Skip Summit and Jeg's for rear end parts.

NullHead

Gotta say, turned out pretty good New Detroit Trutrac, 3.73 Motive performance ring and pinion, Richmond rebuild kit. All I did was put new bearings and races on, and used the stock shims. Pinion is a .030, each respective carrier side got the matching shim. Set turning torque to 15 in/lb, and there you have it. Looks pretty darn good to me, ended up with .009 backlash too.

big gear head

Pattern looks good. Did you mean that the pinion bearing preload was 15 inch pounds or everything together was 15 inch pounds? Can you pull the differential out by hand?

NullHead

Carrier installed with caps torqued, pinion torqued until my turning torque reached 15 in/lb. Did I do that right? The carrier is snug, I need to bump it with my prybar on a ring gear bolt, but after it's popped up a little I can remove it. Snugs back in there nicely with minor tapping on the bearings races to get it seated fully.

Now that I'm thinking about it, I'm not sure I even did that right. Used checking bearings on the pinion, meaning I ground the inside race of the bearing so it didn't need to be pressed on/off during pinion shim adjustment. So when I had everything assembled, and I tightened the pinion nut to pattern the gears, I tightened the nut until I had 15 in/lb turning torque on the pinion nut. For the pattern, I painted them, used pressure on the pinion flange and ran the gear back and forth over the paint several times.

NullHead

OK, so pretty much, now that my pattern is checked, I realize I did this without a crush sleeve and with checking bearings. I figure, next I have to pull the pinion again, press my final bearings on, install the crush sleeve and pinion seal. Assemble everything and turn the pinion nut until all play is gone, and crush the sleeve until the pinion turning torque is 15 in/lb.

I think I was confused about what I was doing, cause I had 15 in/lb without a crush sleeve and was using checking bearings. So, I'm thinking I'm done with my pinion once I press on my good bearings, install the crush sleeve and pinion seal, and torque on the pinion nut until 15 in/lb is achieved.

After that, re-install the carrier, torque the main caps, pre-lube each bearing, and give it a final turning torque measurement.


So, I'm reading through this: http://sethirdgen.org/10bolt2.htm - I have to continue with my pinion preload, and check my carrier bearing preload, then double check total assembly turning torque

big gear head

Before you install the crush spacer do one more pattern check with the new bearings. Be sure to set the bearing preload with only the pinion installed. If the pattern is still good after the bearing swap then go ahead with the final assembly. Don't check bearing preload with the differential installed. The differential should be tight enough that you can not pull it out by hand, but not so tight that you damage the shims or housing when you drive them in. Install the left shim first and then push everything to the left with a screwdriver so that you can get the right shim started. Then carefully tap it in.

NullHead

I really appreciate your patience and wisdom, big gear head! I got everything situated, did exactly as you said. I ended up adding some shims to the carrier, because it wasn't in there right enough. I could pull it out by hand. So I used the guide I linked to and used his formula to calculate carrier bearing preload and got it tightened up. I can't remember the exact number I ended up with, but it fell within the limits he said for new bearings. I rechecked the pattern, and all was well.

So I've already rant he new gears maybe 10 miles and they're nice and quiet The Detroit Trutrac works really well too. I tested it per how the manual said and it worked flawlessly. I'm really impressed overall with how it turned out. Again, thanks for your input and guidance, I REALLY appreciate it!

Motive said to break in the gears for 500 miles of non constant speed, under easy conditions. No towing, road racing, drag racing etc. Once I drive the 500 miles, I'm going to change the fluid, and probably recheck the pattern just for kicks.

big gear head

Great. I'm glad it's working well for you.

Something that I always do is glue a magnet to the inside of the cover to catch metal floating in the oil I use small round craft magnets and use 2 part epoxy to glue one to the inside of the cover at the bottom on the side opposite of the ring gear. You might want to do that when you change the oil.

NullHead

Mine had a magnet on the inside of the cover already, do you mean I should add another magnet to the cover? Right now the way the cover is, the magnet sets on the opposite side of the pump where the ring gear goes.

big gear head

If you have a factory installed magnet then that's great. No need to add another one. GM only put the magnet in the G80 rear ends, so most don't have it.