Rear wheel bearing install failure - help before I ruin another bearing?

[JohnJL]

Hi all,
So I counted and have done 8 of these before, but I encountered a new failure putting a bearing in the rear of my wife's 1985 911 cab...

The trailing arm is out of the car. Using the expensive SKF bearings...went in no problem.



Now, its been a while, but I recall once I had the bearing is, simply insert the inner stub axle from the inside (tranmission side) and insert the outer hub from the outside, then use the castle nut to draw them together. I thought that would concentrate the force only on the inner bearing races as they drew together.

Well, that didnt happen. Both the inner and outer became bound up as they drew together and spinning them once loosened a bit showed the bearing was damaged...it barely spun and was "notchy." When taking them apart both inner races came off partially pressed onto their respective hub and stub axle shafts. I put it all away last night and this morning will remove all the old bearing and start with another new bearing.

My memory is admittedly not great, so I went back and checked the 101 book, the Factory Manual (section 401-20 has the good ole' "installation is the reverse of the procedure") and the site here but still not clear enough to want to take on wrecking more $80 bearings at 5-6 days' delay each.

Did I just get unlucky with this one? I contemplated gently prying the races off both sides of the new bearing, pressing them onto the hub and stub axle separately and then assemlbing, but I didnt see reference to that in site posts.

Can someone pls confirm the proper "install stub axle into rear bearing" and "install hub into rear bearing" procedure? Was I mistaken that once the bearing was installed in the trailing arm, simply using the stub axle's threaded end and castle nut and the hub to draw them together is wrong?

Thanks!

[proporsche]

Hi, John that is exactly how i do it for many years...so you are saying in went crooked?The only difference is , i do it on the car...

can you take a pic of the problem area ?

Ivan

[JohnJL]

Hi Ivan, thanks for the reply.

Those are the best pics I have, and I didnt think they went in crooked. So you also get the main bearing in the trailing arm then draw the hub and the stub axle together using the stub axle's threaded end and castle nut?

[proporsche]

yes exactly like that.....

Ivan

[gomezoneill]

You have to support the back of the bearing while using a threaded rod and press pieces. Cant use the stub axle it will push the back of the inner part of the bearing out.

https://youtu.be/W4wpG7dK1zY

[proporsche]

gome ....i have to admit i do not get your explanation?? i use the axle and the hub to marry the bearing in place ..that is how the OP did it...never failed me..

Ivan

[gomezoneill]

Hi Ivan I always did it like the video shows. Never used the stub axle I installed the bearing in the trailing arm then installed the stub axle.

[911T70]

I replaced a bearing a couple of months ago, using the same technique as in the video, and it went surprisingly well. Putting the bearing in the freezer for a day to shrink it makes a huge difference. Mine slid right in and then locked itself in position once it reached ambient temperature.

[proporsche]

the boy in the video is using his home made tool.Same difference by using the axle and the front hub .....and of course the freezer is alway a plus for the bearing before installment


Ivan

[JohnJL]

Originally Posted by gomezoneill

You have to support the back of the bearing while using a threaded rod and press pieces. Cant use the stub axle it will push the back of the inner part of the bearing out.

https://youtu.be/W4wpG7dK1zY

Thanks guys.

I did it almost exactly like the video, including at 7:45 in where he has the outer hub seated in the outer bearing half, then as he says "uses physics to my advantage" and inserts the stub axle and tightens down with the castle nut. When I did that last part, my bearing seized up and when loosened, fell apart. Maybe I just got unlucky this time, or maybe I didnt have the outer hub half seated deeply enough in teh bearing before trying to draw it together with the stub axle like I have always done and like he does in the video?

Thanks guys!

[faapgar]

Check your bearing that did not seat for enough grease in there.These days some bearings are a little lacking in enough grease.Fred

[Jonny H]

The puller Bisi uses at 7.45 looks too big to be resting on the bearing inner race. If if rests on the back of the swing arm, he was very lucky not to have put force on the inner race and damaged the bearing.

The OP’s procedure sounds right to me.

[Solamar]

I was taught to only set bearings with the outer race. Pressing on the inner race of standard bearings can damage them.

The rear bearings on 911s are not standard roller bearings or tapered bearings, they are a unusual double pair with play, that after the outer race is set, the stub bolt tightens out the play.

I'm not 100% certain, but I think seating this style bearing by the inner race could damage them.

[JohnJL]

Originally Posted by Solamar

I was taught to only set bearings with the outer race. Pressing on the inner race of standard bearings can damage them.

The rear bearings on 911s are not standard roller bearings or tapered bearings, they are a unusual double pair with play, that after the outer race is set, the stub bolt tightens out the play.

I'm not 100% certain, but I think seating this style bearing by the inner race could damage them.

We are all talking about here after the bearing is seated - by the outer race - in the arm already. Once that is done, how to get the outer hub and inner stub axle installed without destroying expensive bearings.

[GAJon]

Originally Posted by JohnJL

We are all talking about here after the bearing is seated - by the outer race - in the arm already. Once that is done, how to get the outer hub and inner stub axle installed without destroying expensive bearings.

I think the video covers that in using the threaded rod to pull the outer hub on the the outer bearing race. To do this without damaging the bearing, you have to support the inner race on the other side of the threaded rod.

You could easily mess this up by placing your inner support on the trailing arm housing instead of the actual bearing race. That could cause the outer hub to push on the inner race as you tighten it and unseat the inner race.

Once you fully seat the outer hub, using the inner hub to seat the inner race is easy with the axle nut.

FWIW, I think once the race is unseated, the seal can become damaged. If this happens, the bearing life is probably shortened and would need replacing.

I just went through this same ordeal and ended up paying someone to seat my bearings with a shop press after unsuccessfully inserting one of them slightly crooked following that same video. I think this was difficult to do with so many washers and alignment issues with the arms out of the car. May have been easier if the arms weren’t flopping around on my shop bench...

[Solamar]

Originally Posted by JohnJL

We are all talking about here after the bearing is seated - by the outer race - in the arm already. Once that is done, how to get the outer hub and inner stub axle installed without destroying expensive bearings.

Gotcha,

I used a hydraulic press to insert the hub, supporting the inside inner race

[911T70]

Originally Posted by JohnJL

We are all talking about here after the bearing is seated - by the outer race - in the arm already. Once that is done, how to get the outer hub and inner stub axle installed without destroying expensive bearings.

I had placed the hub in the freezer to shrink it. It slid into the bearing with little force.

[ClickClickBoom]

The FSM is kinda fussy talking about presses and stuff. I couldn’t take my trailing arm off due to the CZU fires. Here is my take on the process:
http://forums.pelicanparts.com/porsche-911-technical-forum/1072785-rear-wheel-bearing.html
I did mine on the car, using freezing and heat. Physics is your friend. The arm and outer bearing race are an interference fit, or really close to it. The bearing install/remover kit I listed makes it ALMOST idiot proof, I am the almost part.

[proporsche]

i looked at it again and the only thing i can see you most likely did wrong is ,that you did not have the hub and the axle aligned - the teeths.....
Other than this it should be a no brainer.....i have never ever had to use any special tools for this job..

Ivan