rjmcgee

OK, I just got my new 4.10 gears set up tonight and when checking back lash I have .002" - .005" on the ring gear. I am thinking that I will run it this way because I'm not sure what I would have to have in the way of shims to get a couple thousands more backlash. The mesh also looked good. Pinion gear is installed good with a solid bearing spacer and 20 - 25 inch-pounds pre-load. Does this all sound about right or am I way off. I have no written info on setting this thing up, just what I have searched on here, so if Ede and RB could chime in with their knowlage, I would appreciate it.

ede

if your pinion depth is correct you would need to move the carreir shims around, you don't add or take away carrier shims, just change the arangement. i'd shoot for a back lash more around .008. what back lash did the gear maker say to run?

rjmcgee

Only have two carrrier shims and one is about .020" thicker than the other. It was way too tight with them set up the other way. The gears are an E-bay item. I have no manufacture info except that they are made by Yukon. I paid $50 plus shipping and thought that I was buying a used OEM gear set but the are brand new. I understand that by buying no name parts like this the rear end may not last as long as it could but there is no better way to learn how to set one up than trying.

ede

get some carreir shims that total the same thinckness as what you have and move them around to change back lash. do you know your pinion depth or did you just reuse the same shim? you maybe able to change the pinion shim also if you just guessed at a depth.

RB83L69

I agree, sounds to me like you need to get a shim pack and experiment.

Correct backlash is .005" - .008". I'd rather have a little too much than not quite enough; the gears "grow" when they heat up, so the backlash decreases while running, so if there's not enough, you will eventually get into a situation where there's "negative bcaklash", if you get the drift.... gears won't last long like that.

http://www.drivetrainspecialists.com...=28&cat=GM+7.5 Shouldn't be too hard to find a carrier shim kit, or one of those install kits without bearings.

rjmcgee

I guessed the pinion depth with the old shim. I was going to measure and set the depth but I don't know what the pinion depth is suposed to be. I read in a search where Ede talked about the pinion depth being stamped on the pinion but it was not stamped on this pinion gear.

I have a ring gear spacer from Drivetrain Direct and come to find out they don't supply bolts with their spacer. Try finding some 7/16 - 20 left hand thread bolts that are .250" longer than stock.
So I ordered anoth spacer from a differant outfit that had bolts. Anyway one spacer is .300" thick and one is .309" thick. I have the .309" one in there now, but what if I put the other spacer in?Is that way too much of a differance?

I have a big timeline problem here as I am trailering this car up to a big F-body gathering next weekend. Thanks again for the help.

RB83L69

You do not necessarily have a timeline problem. You can have stuff at your door on Tuesday morning if you need it, and have your car in perfect working order by noon Tursday. Should be no issue with all of that.

In my experience, a .035" pinion shim will work about 99% of the time in these rears. In fact, I have never yet seen a 8.5" or 7.5" 10-bolt that came from the factory with anything other than a .035" shim, or needed any other size when put back together with any OEM spec gears (Motive, Superior, Dana, USGear, etc. - NOT including the Richmond racing gears however, those can be quite different). So if you put it back together with a .035" shim, odds are very good you're OK there.

I don't recall ever getting gears for either of those kinds of rears that had anything stapmed on them, that was anything that I could decode as a depth setting; ones for 9" and 12-bolts I've seen that alot, but not these.

Trying to put rears together with a bunch of factory cast-iron shims is just about futile, if the shims didn't come from the housing you're working on. I have no idea myself how they do that at the factory, unless they have some kind of machine that spits them out specifically for each individual housing, as the housings roll down the production line, based on some measurement of the housing. Since, after all, the tolerances on gears and carriers is very close, and it's really the housing you're shimming, not the carrier; think of the process as being, that you have a very accurately cut set of moving parts that you locate in space as they need to be, and a very sloppy center section that you're trying to fit around the other things, and you're shimming the center section to true it up to the moving parts.

.300" sounds to me like the correct spacer dimension. Not that it matters very much; shimming will clear that .009" up easily (.009" more on the left and less on the right). In fact, .009" of spacer, should result in about .004" - .005" change in backlash. You might find in fact that if you just took exactly what you have and swapped to the thinner spacer, your backlash would open up to right where it belongs. IMO anything up to about .010" of backlash is probably OK, although much above that point you'd start to be able to feel it as drive train slack.

rjmcgee

Alright that helps clear some things up. I think I will swap that spacer around and see what I get. I am using all of the same shims that came out of this housing. Thanks again.

rjmcgee

I changed the ring gear spacer to the thinner one and that got me .013" backlash. So it looks like some differant spacers are a must. I thought about turning down the thicker spacer 2 or 3 thousands but when I chucked it in the lathe I can't get it to run true enough, looks like it is time to true the jaws on the chuck.

rjmcgee

Took the thicker spacer down to work and had a friend show me how to get it chucked up accurately in his lathe. We took .0035" off of it and when I reinstalled it I now have .008" backlash. Freaking perfect. Thanks to RB and Ede for your help on this.