Differential sound after rear end refresh

[OldRanger]

E36 rear bushings can be used instead of replacing an entire diff cover if on a budget.

I'm interested in the details on this. What is the part number and are there any modifications to the part prior to installing in the OEM diff cover? Does it require a different bolt? (etc.)

I'm dealing with a noise problem on my daily driver. A bit of background: I've put new diff bushings on two different E46M3s, both with the subframe still installed and the car on jack stands/quickjack. On the first car (at 150k miles) with a freshly rebuilt differential I used a BMW OEM front bushing and Powerflex rear bushings. I used Powerflex rear bushings to save about $100USD. The car still has OEM noise reduction and trunk mat. On that first car there is very little diff noise. On the second car (also at 150k miles) with an adequately functioning original differential (not rebuilt)....I used ECS bushings front and rear (88A durometer polyurethane and Black anodized 6061-T6 aluminum sleeve) I made this decision to use aftermarket bushings to save $100 and make the install easier. I recalled how shi##y of a job removing a destroyed front bushing is while working under the car without the ability to access the front bushing from the top of (a removed) subframe. So I took some risk and decided to same some money. Bad idea.

The ECS bushings produce absolutely obnoxious noise at speeds in excess of 60mph. It is literally painful to my ears. To keep things 'fair', I have replaced the brittle OEM under-set noise reduction material with two layers of 80mil butyl sound deadener and it does not help. I've put two layers in the forward part of the trunk as well.

I am pulling the diff and getting those bushings out. This time I'm going to hire help to sit in the car and take the transmission in/out of gear while I pull the bolts on driveshaft and axles. Getting up and down is a hell of a work out.

[OldRanger]

In retrospect, I don't believe there could possibly be any benefits that justify the awful noise of the ECS bushings. Objectively, the drawbacks of using OEM bushings are very few and it boils down to adding some cost and a 24 hour wait on the cover sealant. These are the details:

1) Using a new OEM differential cover and front bushing, the job will cost approximately $120USD more than using aftermarket bushings.
2) Depending on your tools, IF the subframe is still on the car, it might take longer to install an OEM front bushing. This is probably a net-zero because you wont have to spend any time extracting the rear bearings
3) You will have to let the new diff cover sealant cure. This will add wait time to the job.
4) You may regret not having your differential rebuilt while doing this. (On a high mileage car)

I will report back after I have OEM bushings installed. I'm going to install a complete OEM diff cover and front bushing. Yes, the car feels good now, and it will be important to me to retain the improved shifting I've got now with the ECS bushings (it's less notchy and no clunking). I predict that fresh OEM bushings will offer the same driving feel. I've got the parts on order, but not sure when I'm going to do it.
First, I've got to redo my valve cover gasket. When I did a valve adjustment...I used Elring. It's leaking at the half-moons in the back. (Ugh)

(Note: I'm feeling the pain of the age old saying "if you don't have time to do it right, when will you have time to do it again?"

P.S.: I'm going to go check if there is a sticky thread on what parts NOT to use.

[bigjae46]

I’ve long said…poly is a waste of money.

OEM - quiet, compliant wears out
Solid - noisy, limited movement, doesn’t wear out
Poly - noisy, compliant and wears out. Also can’t withstand excessive heat.

So poly takes the downsides of OEM and Solid then combines them into a mushy heaping pile of garbage.

I’m sorry, putting poly anything on the car is a stupid decision.


Sent from my iPhone using Tapatalk

[Ddavies564]

OldRanger, I’m in the same boat. Originally my car had 95a powerflex rear diff mounts and an oem frt mount. Car had close to oem sound levels. Recently rebuilt the diff and put in fresh powerflex frt and rear mounts and the noise was substantially louder than prior to the refresh. I heard about the e36 mounts on here and also saw a popular diff builder in the uk recommend the e36 oem mounts. Im gunna pull my diff this weekend and install and oem frt mount and e36 rear mounts. See how it goes.

[OldRanger]

Thanks for chiming in Ddavies...maybe the front bushing is the primary concern with noise. Bummer...It's a PITA to deal with when the subframe is on the car.

[Ddavies564]

Switched out the powerflex 95a bushings for oem e36 rear and oem front e46 bushing. Easy to switch out, pressed right in and bolted up like normal. Back to oem sound levels and the cars felt the same in terms of power delivery. Kind of a no brainer, all in cost was about 70 bucks too. I’ll keep a look out for any wear.