Dimi 944

Thanks to Rennlist, for the last 4 years of ownership I have been able to maintain and fix almost everything on my '86 944 NA. I do not post much but I think that this write up might help the 944 enthusiasts who plan to tackle the rear wheel bearing replacement.
With a substantial help of one of my 944 fellow friends we were able to replace both rear wheel bearings in about 4 hours. The main reason to replace the bearings was that the driver's side one started making the typical "wobbling" noise in hard turns and was pretty much done as it turned out during its replacement.
My friend convinced me to do the passenger's side as well while we were at it.

So, this is how it went...

First, we loosened the axle nuts with the car on the ground and the brake applied. We used a BIG torque wrench (capable of up to 500 lbs torque) for this job. Then, we placed the car on a "scissor" lift that my friend had recently acquired and it made the job definitely easier.



The rear wheels were removed...



then the calipers, rotors and rear axles were removed.

At that point, a standard slide hammer from Harbor Freight was used to extract the stub axles.



Then, we used a bearing tool to remove the wheel bearings after the retaining c-clips were removed.
My friend actually made the tool set for removing and inserting the bearings, and it took no more than 30 seconds to extract the bearing with an impact gun. The tool works with a wrench as well but it is slower.

The tool set...


removing the bearing...


old bearing removed....


and the control arm with the old bearing out.


Next, we moved to the new bearings installation. The new bearings were in the freezer while the old ones were being removed. The installation is easier while the bearings are still cold.

Ready to install the new bearing with the bearing tool...


inserting the new bearing...


new bearing installed.


After that, we installed back the stub axles by using an impact gun and the old axle nuts just to get them snug. Then, the new axle nuts were used and torqued as much as possible with the impact gun. The rear axles were installed back as well as the rotors and the calipers. The rear wheels were installed and the car lowered to the ground. We used the BIG torque wrench to torque the axle nuts to 368 ft/lbs. After test driving the car the torque of the axle nuts was checked.

All and all, the whole job went pretty smoothly. I could not find other write ups for rear wheel bearing replacement so I hope this one serves as a general guide to how this job could be done.

Thanks for reading and have fun wrenching!

Olli Snellman

Great write up.
if someone is planning the similar project, some money can be saved when using BMW E34 bearing which is the direct fit.

kartiste

Please describe the "wobbling" noise. My 84 makes a "womp-womp-womp-womp" coming from the back, whose frequency increases with speed, but it makes it just going down the road, and it doesn't change noticeably when turning. Also, I am having trouble locating the noise, LH vs. RH. Is this noise consistent with worn rear wheel bearings/stub shafts or could it be in the transmission?

Van

Great writeup Dimi. I've used the SIR tool, and it really makes it an easy job.

Kartiste, yours could be in the transmission...

Another way to tell it it's a rear wheel bearing is if you're experience brake pad kick-back - if the brake pedal moves farther to engagement after hard cornering in one direction vs. the other direction. As the g-forces load up wheel, the wheel tilts in the bad bearing, and the tilt causes to brake rotor to push the pads a little farther back into the caliper. When you step on the brake, the pad has to first move up against the caliper before it can squeeze.

kartiste

I'll try the pedal travel test - thnx. But if the tranny, what would be the culprit, and roughly how difficult to fix? $$$ or $?

Appreciate your help.

PS I have the factory manuals, including gearbox.

Van

A failed tapered bearing. Usually one of the ones that supports the diff/output flange.

If it's on the driver's side, you'll have to pull the gear cluster out to remove the diff. If it's on the passenger side, you just need to remove the cover to access it.

However, while just changing the bearing will get you back on the road, it's quite likely that you'll have to adjust your backlash/pre-load for the ring and pinion. If you've looked at the factory service manual, you know what I mean.

At that point, you're pretty much looking at a fully tranny rebuild in terms of labor... and you might as well replace synchros while you're in there... Sky's the limit for how much you can spend. Might as well rebuild the diff, too.

kartiste

Hoo boy. I guess a lot rides on isolating the problem. Is this as good a tool as any? Anything better/cheaper?

pnbell

It's very difficult, and easy to mis-diagnose problems based on "Noises" spelled out rather, than actually heard... HA ha ha.

This could simply be your rear tires have flat spots... Or your exhaust is resonating creating a strange frequency...

When you hear this noise, put the car in neutral, and let the engine fall to idle; does the noise change?

pnbell

p.s.

Dimi, Great Write Up!! Thanks for putting this Together and Sharing! Hope all is well!

John_AZ

Fantastic pictures and information.

Thanks for taking the time.

Thanks Ollie for the rear bearing interchange.

It would be a good addition to the Rennlist "Parts Cross Reference" list:

https://rennlist.com/forums/924-931-...reference.html

John

Dimi 944

Thanks Van! I actully did not know that SIR Tools make a special tool for this job. Looking at the cost of the SIR Tool, I consider myself lucky that my friend was able to fabricate one and use it for my car. He also mentioned that it did not cost that much in terms of materials to make the tool.

lbpalm

I have a perplexing rear axle bearing installation problem and thought someone might know the answer or be able to point me to the right direction.
I recently got my 944T sideways in an event and when the contact patches hit a seam in the track pavement a rear bearing was damaged. There was no other damage to the car other than the tire needed to be re-seated onto the rim (it did not knock clear off).
So, while the off ruined an otherwise great day, it was not catastrophic to the car.

To remove/replace the damaged rear axle bearing, I purchased the Sir B90-P02 tool set which seems to work fine
- Here is my problem:
1. I have been able to extract the stub & remove the bearing remnant from it.
2. I also removed the bad bearing from the trailing arm with no issues.
3. I then installed a new bearing into the arm with the indicated SIR disk #12 (watching & measuring installation alignment closely) and the bearing appeared to install correctly.
4. I then re-installed the stub with the indicated SIR disk #14 and the stub appeared to install correctly.
5. Now re-assembled, the stub wobbles 3/8 inches or so, just the same as when the broken bearing was in the trailing arm!
Thinking I did something wrong, I took it all apart & re-did the job with a second new bearing. This time, before re-inserting the stub, I examined the bearing for play/damage, and sure enough, the second new bearing also had significant side to side play. Thus, it appears that I am doing something very wrong which is damaging the new bearing at the time of its installation to the trailing arm.

I have been careful to follow the Sir Tool instructions, and have also cross-referenced their instructions with other instructions found on-line, but I must be doing something incorrectly.

Might any bearing installation pros have an idea what could be causing the described bearing installation failure? Have you ever heard of or seen this 944 rear axle bearing installation scenario?

Thanks in advance for any help!

por944s2

Just did the rear bearings on my 968. I would recommend using 04 Box S rear bearing in place of the stock one. It's a better bearing and is exactly the same size, and cheap as well.... The Arnworx tool and an impact makes this easy!!

Dimi 944

Thanks for the good info!