rear diff bolt keeps braking.

[contie92]

My rear diff bolt keeps snapping. ive replaced it twice now going on the 3rd time. i cant seem to find anywear with a stronger bolt or a support bracket to help prevent this. If anyone has found a cure for this please lend my some insight. thanx

[Redd]

Have u done solid subframe bushes? What diff bushes are you using?

[ha9981]

Originally Posted by contie92

My rear diff bolt keeps snapping. ive replaced it twice now going on the 3rd time. i cant seem to find anywear with a stronger bolt or a support bracket to help prevent this. If anyone has found a cure for this please lend my some insight. thanx

How long did it take to break again?

It seems the problem hasn't been sorted yet. Others had the same experience

[amrazM]

diff bushings.

[Siajoon]

Get some solid subframe bushings and it should remedy the issue you're having.

[DJiGGs]

What symptoms do you get when a diff bolt breaks ? Is it pretty noticeable while regular driving or only when you are pushing it?

[rebelliousfb]

Very noticeable, especially when you're pressing or letting off the throttle (clunks as the driveshaft bounces around). This guy's diff bushings must be made of jello and he must be launching hard daily

[amrazM]

Originally Posted by DJiGGs

What symptoms do you get when a diff bolt breaks ? Is it pretty noticeable while regular driving or only when you are pushing it?

A lot of funny noises/feels while driving

[ha9981]

Originally Posted by rebelliousfb

Very noticeable, especially when you're pressing or letting off the throttle (clunks as the driveshaft bounces around). This guy's diff bushings must be made of jello and he must be launching hard daily

Not exactly related to abuse, it's been happening to others too. MRF claimed they were making some reinforcement of some sorts then it went quiet. It seems to be a rare flaw some of these cars have that's recurring. There is another thread in here.

[DRLane]

Originally Posted by ha9981

Not exactly related to abuse, it's been happening to others too. MRF claimed they were making some reinforcement of some sorts then it went quiet. It seems to be a rare flaw some of these cars have that's recurring. There is another thread in here.

This has already been solved.

[ha9981]

Originally Posted by DRLane

This has already been solved.

I guess it seems this case I'm about to share is more abuse related. But they shouldn't break that easy.

https://www.bimmerpost.com/forums/sh...php?p=26705163

[DRLane]

Originally Posted by ha9981

I guess it seems this case I'm about to share is more abuse related. But they shouldn't break that easy.

https://www.bimmerpost.com/forums/sh...php?p=26705163

The car has a lot of power, and those diff bushings are a joke (the rear one is foam). If you launch the car with DTC and wide sticky tires you're likely breaking bolts. Get solid aluminum diff and subframe bushing and problem's solved. The diff whine is the trade off.

Good except from AKG Motorsports to keep in mind. "Remember: The material used for the subframe bushing location(s) must match the material used for the diff mount bushing(s)."

[pbonsalb]

The rear bushing is not foam. It is solid aluminum with a roughly 1/8” thick foam sleeve. I think the problem that a few people have experienced is related to more than just that single rear bushing.

I don’t think the subframe and diff bushings have to match. You can run solid or very stiff (like Delrin or 75D poly) subframe bushings with stiffer than stock diff bushings like 80A or 95A or 75D poly. It’s the stiffer diff bushings that cause the whine, not the stiffer subframe bushings.

I run 75D subframe and 95A diff bushings. There is whine, but it is tolerable to me. I would not go any stiffer on the diff bushings. I did drive a convertible with solid subframe bushings, however, and thought the whine was tolerable. Maybe the convertible is better insulated?

[DRLane]

Originally Posted by pbonsalb

The rear bushing is not foam. It is solid aluminum with a roughly 1/8" thick foam sleeve. I think the problem that a few people have experienced is related to more than just that single rear bushing.

I don't think the subframe and diff bushings have to match. You can run solid or very stiff (like Delrin or 75D poly) subframe bushings with stiffer than stock diff bushings like 80A or 95A or 75D poly. It's the stiffer diff bushings that cause the whine, not the stiffer subframe bushings.

I run 75D subframe and 95A diff bushings. There is whine, but it is tolerable to me. I would not go any stiffer on the diff bushings. I did drive a convertible with solid subframe bushings, however, and thought the whine was tolerable. Maybe the convertible is better insulated?

It's very soft and the only bushing that you can press out with ease.

Of course you can do whatever you want, that's just what's advised by this specific race parts company. Lots of folks running solid sub and softer diffs to minimize whine. But you're not solving the problem of movement if you're launching the car.