tommo951

I have just got back in after a 40 mile round trip and can hear the tell tale sounds of rear wheel bearings starting to rumble. Has anybody got any tips for changing these? I have a pair of them in the garage as the previous owner of the car had hoarded parts in case he ever needed them, I ended up getting 2 large cardboard boxes full of new parts when I got the car!!
Are there any specialist tools required or is a blacksmiths shop job???
Any tips greatfully received

Cheers
Tom

Sam Lin

A special puller makes it a lot easier - the $300 Porsche tool now has a reasonably priced alternative, Bruce at Arnnworx just released it for $90.

Sam

tommo951

Hi Sam,

Is it an essential or will a good puller set with attachments do the job?
Bruce's tool sounds cheap enough however the shipping to UK and the waiting time is probably gonna be prohibative as I want to get it done before it gets any worse

Cheers
Tom

Red1

Clark's Garage has a good write-up on the technique.

The correct puller will help you get the old one out without damaging the control arm, but it's not the only way to do it.

For insertion of the new bearing, I did the heat control arm/freeze bearing trick. Worked like a champ.

DAR951

If you're changing the bearings with the rear arms still on the car (as opposed to the Factory proceedure) then the special tool is pretty much essential, not only to remove, but to install the bearings as well (very easy to get them cocked and tear up the soft aluminum w/o it). The only alternative to the special tool is a slide-hammer-puller (unless the arms are loose and then you can use a press).

Just did this exercise and gave up on the slide hammer when I couldn't get them to budge. With the SIR tool they came out and went back in like they were on butter.

Another thing to note is that the rear axle nuts are torqued to almost 400 ft.lbs. That's no typo, almost four hundred! Since not many folks have torque wrenches that go that high, seems the most common proceedure is to just gun the hell out of them, making them really easy to remove later... not. Be prepared with 3/4 inch breaker bar and pipe or a big gun and a good compressor. I'm sure I voided the warranty on my gun that is supposedly rated at 600 ft.lbs. in reverse by having to run the pressure up to 150psi to break those suckers loose.

Good luck.

mark944turbo

Well, i did mine using no special tools, but if I were doing it again I would buy a puller. I just whacked the races out with a punch and hammer after burning out the insides of the bearings with propane. It wasnt fun.

Red1

I used the SIR tool to get them out, but didn't need anything special to put them in. Put the bearings in the freezer, heat the control arm with a propane torch for 10 minutes, then the bearings slid all the way in to the stop. One of the local race shops told me if I did it right the bearing would go all the way in without forcing it. They were right.

UK952

I took my hub to the OPC (official Porsche centre) to get the inner race remnants pulled off the hub (around £12) the rest is relatively straight forward with the right size bits of ally to use as a drift.
Tony

tommo951

So basically if I warm the hub casing up with a gentle acetalene flame and then use a slide hammer and some wurth Rostof Ice on the bearing it should come out ok. Then freeze the new bearing freezer (or in the bands smoke machine "dry ice"!) Then reheat the casing and the bearing goes in easily????
Right then its time to stop talking and get the job done!!!

Cheers Guys, I'll feedback once its done!

Rich Sandor

I'm not an expert, but I'd be a little worried about shock cooling..when metal cools TOO quickly it often cracks.. I'd be carefull with the dry iced bearing and hot hub.

This is an operation I'm going to have to do soon.. however because of the torque the rear axle requires, I MIGHT just take it to the shop...

Red1

Don't take it to the extreme. The household freezer is plenty cold enough - no dry ice needed. Also I used a propane (butane) type of torch to heat the arm. I wouldn't suggest an acetylene torch. Spent ten minutes heating the arm, grabbed the bearing from the freezer, and stuck it in. The bearings were chilling only for the time I was heating the arm. It doesn't take much.

The mechanics that suggested that procedure to me are widely regarded as one of the best shops in this area. I was impressed with how well it worked.

tommo951

Shock cooling is not really a problem with steel in the same way it is with Cast Iron or Alloys (Yes before anybody says it, I know steel is an alloy)
Obviously there are different grades of steel for different purposes e.g EN24B which is usually used for Forged Crankshafts. Now this steel would be prone to shock cracking in the situation mentioned. However the steel used in bearings is probably going to be of the grade that would actually case harden under the situatuion mentioned. Think about case hardening (nitriding) this is essentially a heat shock process. What it comes down to is the grade of steel and its application. In the instance of a wheel bearing that is located near one of the potentially hottest areas of the car (brake disk) but can then be cooled by driving through water you are going to get quite rapid heat changes hundreds of degrees in maybe seconds therefore the type of steel used in manufacture will be of a durable nature.

Cheers
Tom

Come on then all you metalurgists come and tell the whole story!

UK952

Forgot about the hub torque (skirting the metalurgy) I needed a very long extension to get mine undone (6 foot) forget the figure but between 300 and 400ftlbs.
Tony

tommo951

Tony,
I have an Ingersol Rand Impact Gun it is rated at 650lb/ft. It takes off Land Rover Front Pulleys and those things unually need 6ft bars. I am lucky enough to have a britool 5ft Torque wrench so should be able to get the torque spot on.
cheers
Tom

Red1

Tom, the torque on the rear axle nut should be 368 lb/ft. (500 Nm)