I'm replacing my 89 formula posi unit with a 84 10bolt standard rearend. Yea I know it sounds weird to go backwards like that but it has to be done. I'm just starting out learning how to rebuild rearends so I'm not sure on many things.

The question I have is that before I take apart the 84 rearend i need to check the tooth contact pattern. I've heard and read that you need to load the gears to get a proper reading. The manuals want you to apply the parking brake until you have resistance at the pinion gear. That's fine except I have the rearend out of the car.

Is there anyway to load the gears like this while the rearend is out of the car?

 

That's news to me.

Here is what I did. Take out the pinion gear and get the bearing off of it. That shim under the bearing goes with the rear end housing it comes out of. Gears, axels, and carriers are precision made parts, the rearend housing isn't. If you take the gears out of a rearend and put them in another then you need to check the pinion depth and see if you need the shim from the doner housing.I never even measured the pinion depth because I had no idea what it should be, wasn't marked on the pinion gear like I heard it would be. I just made sure to use the shim on my new pinion gear. Put the shim on the new pinion gear and install the bearing. Install pinion gear in housing and set preload perferably with a solid spacer and not a cruch sleeve. Install new ring gear on carrier and install in housing. Shim carrier until backlash is correct. If you do those things right then you should be in good shape.

Hope this helps.

 

read my other reply

 

Ok I can see why this sounds confusing. I have a 89 posi rearend in my car right now. I need to get rid of the entire 89 posi rearend. I have another rearend from a 84 Trans am. The entire rearends need to be swapped. But I want to check everything in the 84 rearend to make sure that it is good. Since it has been sitting in my backyard for many years. Before tearing the rearend apart I want to diagnose if it is good or not. So thats why I would like to test the tooth contact patch.

Does this make more sense? I need to find a way to put a load on the axles(gears inside) so that I can get an accurate reading from the pinion and ring gears when I do the test.

 

no point trying to help someone that won't listen

 

Read what Ede said again. It doesent matter, as long as there is no visible damage to the gears of bearings it will be fine. There is no need to put any type of load on the gears to check the contact pattern besides the factory is pretty darn good at setting up rear ends at least GM is.

 

Thanks for your replys. I know what you guys are saying that it doesnt matter and that you dont need to load the gears. I understand that. I'm just trying to figure out if there is a way to simulate tension on the gears. I have the rearend out of the car so I cant apply the parking break to put that tension into the system. Im just looking for some creative ideas since my parking break isnt hooked up right now. Thanks.

 

since you now know it doesn't matter why do you still want to do it?

 

Ok. THanks for everyones posts to my difficult question. Its good too have people out there that know alot about these 3rd gens. Im still learning everyday and trying to build better cars.

I think what I'm going to try to do with this one is install the rotors back on the rearend. Then I think I'll just try and put c-clamps on the rotors and the backing plate of the rearend. I'll let you guys know how it turns out. Thanks