Help with 7.5 gear and posi swap

[Texas82GP]

Yeah, I still don't totally understand where I went wrong. I tested the preload with an inch pound torque wrench and thought it checked. When I had a pro re-do it for me I asked him where I went wrong and he told me I hadn't crushed the crush sleeve sufficiently and that the pinion was loose.

 

[Turbo Zach]

I have used greece the same way as dye. You can also buy shims instead of crush sleeve. The preload on the pinion is because new bearings will loosen up as the run in. If the preload is too loose it will make the berains too loose when they are run in and take pinion seal out or worse. Used bearing will need a lighter preload than new bearings. If I was building a rear I would buy new bearings and install kit. Hope I make sense.

 

[Bonnewagon]

Yeah, grease will work. But how do you know how many shims to use? The crush collar is a collapsible spacer that can be described as an adjustable washer. As the pinion nut gets turned in, the collar crushes, and the pre-load on the bearing can not become less. The pre-load is a bit hard to grasp. Imagine the gears being held in suspension, so tightly that even the motor's power can't deflect them out of position. The purpose of this is so that the gears relationship does not change- ever. The bearings are designed to be loaded that way and still run quietly. The bearings will wear eventually, but with proper lubrication, that will take many thousands of miles. And to account for that, the used bearings and gears pre-load is slightly less. So the pre-load on the carrier and the pinion is critical for proper operation. Jared, did you change bearing races? You need to really bang them in with a soft drift so they are seated. Did you have the brakes totally backed off?

 

[Turbo Zach]

You answered your own question. A crush sleeve is a spacer not a spring. Shims you can take out or add to achieve what you want. A crush sleeve is a one time deal. Did not mean to sound rude if I did.

 

[Bonnewagon]

No, not rude at all. I'm just trying to clarify. I never said it was a spring, that would never last in a rear. To use washers, you would need to start with the thickness of the original crush collar just to get in the ball park. Then you would need to add or subtract washers until you had the correct pre-load. How many times are you going to remove the companion flange, the pinion nut, outer bearing, and dig out washers without ruining that new seal? Seems like a lot of extra work when a crush collar just goes in once, is set, and left alone. It's not like they are hard to get and usually come in any decent parts kit. I think even the HELP! parts line has them.

 

[pontiacgp]

Mark, we replacedf the crush sleeve on a few 7.5 rears on circle track cars. The way we did was to measure the crush sleeve and install the same length in washers

 

[Turbo Zach]

Yeah, I still don't totally understand where I went wrong. I tested the preload with an inch pound torque wrench and thought it checked. When I had a pro re-do it for me I asked him where I went wrong and he told me I hadn't crushed the crush sleeve sufficiently and that the pinion was loose.

When measuring the torque on the pinion. That is rolling torque. How much force that is needed to keep rotating, NOT initial torque to get it started. Big difference between the two. A dial torque wrench works good for that. A old fashioned torque wrench with the beem and pointer will work too.

 

[Rick_B_86]

I also went with the solid bushing and shims. It just seemed like a better setup than crush sleeves, but that's just my opinion. But it's way more time consuming to set them just right (especially when you don't have the original crush sleeve to measure off of) and like Bonnewagon stated, you do run the risk of damaging something in the process.

 

[gbondo57]

A simple rule. If you change 1 gear set to another housing, This is the key. The pinion bearing, shims on that bearing, and crush sleeve that are IN THE axle/HOUSING you are using, need to be used, on the pinion you are installing. Someone else has already done the "setup" on that housing. The crush sleeve can be reinstalled backwards, I've done it. Burr on one edge would not let in sit flat. It caused end play. 99% success rate. Then backlash setting talked about earlier. good luck.

 

[pontiacgp]

A simple rule. If you change 1 gear set to another housing, This is the key. The pinion bearing, shims on that bearing, and crush sleeve that are IN THE axle/HOUSING you are using, need to be used, on the pinion you are installing. Someone else has already done the "setup" on that housing. The crush sleeve can be reinstalled backwards, I've done it. Burr on one edge would not let in sit flat. It caused end play. 99% success rate. Then backlash setting talked about earlier. good luck.

the housings are the same, the shims travel with the carrier, not the other what around. Turning a crush sleeve around makes no difference and there is no front or back to a crush sleeve