Carrier bearings installed with heat?

[96eb96]

Please fill out the following to ask a question.

MAKE: Ford
MODEL: 8.8 axle
YEAR:
MILES:
ENGINE:
DESCRIBE ISSUE....

I don't own a press. So I drop off a new 8.8" carrier with a trac-lok to get those tapered bearing pressed on. I asked if they have a press, they said yes. Many places won't even bother with it. Ok, so I get it back all nice and installed and the bearings look totally blue and races cooked well done. Guy said there is no problem doing it this way - even if you were to race. Sure they say not to do it but in the real world it don't matter.

Anyway - should I pull the bearings and look for another place(the bearings are cheap, and I can salvage a driver from one of them too at this point). I don't want failure in a few months, but I'm not looking for 20 years. I won't be keeping this truck forever (maybe 20K at most as a back up truck).

Or, is it fine to leave it as it is. It is a daily driver. I put the outer race on with some gear oil and its very smooth.

 

[nickb2]

To be honest, I am not sure about this. I would say that if they were blue, then I would suspect the the metal has now been permanently altered and is now brittle and has lost its elasticity. I think "tempered" is the word I am looking for and those bearings are toast in my opinion. Or a bet to say the least.

No way of knowing if they tempered to the right hardness again. No way of knowing how high the temps got and blue steel means they got over 450F or so. What was cooling time etc.

Bearings are usually if not always made of 52100 alloy steel. They have already gone through a specific furnace quenching and tempering process which is strictly observed to application specs.

Nother thing to consider, why, if they had a press, did they feel the need to heat them. I have heard of heating bearings in an oven at 200F for a few mins but have never felt the need to do as I have always used a press for such jobs.

So, my uneducated opinion is that I would not use them for a client. As a back up car for yourself, the only hurt that may happen is a shattered bearing as there is now no way of knowing if the alooy was altered out of 52100 specs for bearing applications.

Maybe someone here with more technical education in alloys/metallurgy can expand and say if they are good to go or not. I suspect that most ppl in my trade would not want to risk it for an automotive application where such axial strength is needed and the tensile strength may have been altered.

 

[nickb2]

To further hit home what I mean, I did some research.

Typical 52100 bearings have a HRC factor of 60-67HRC. Temperature limit for 52100 chome alloy steel is 300-400F and again uses a special treatment process to achieve the max temp for maximum hardness and a bearing needs to be hard to prevent indentation, not brittle like cast iron or soft like brass.

The higher in temps, the lower you get on the HRC scale. So do some research on the rockwell scale

 

[96eb96]

I'm sure these were heated way above 400 from the way they look. I honestly don't know why he didn't use the press or if he even has one. You drop something off, you expect them to do it right. This is more of a small operation.

I think I'm going to change them - this time at a reputable machine shop. It is not really expensive, Timken bearings are $10 ea.

 

[kev2]

96eb96. replace bearings, forget the academics the reasonable cost will buy you peace of mind and ability to sleep.

A learning experience the shop was tested and failed you.

Have a merry Christmas

 

[96eb96]

I put the carrier in the icebox in a bag to shrink it. My neighbor was a Jeep/Dodge tech and he said with the right driver (old race and a bearing driver there is no problem - and it is specified in the Jeep FSM along with a numbered tool for a driver) its fine to hit on the inner race, same as an axle bearing where you strike the outer(no other way to install). He said heavy acceleration is going to put plenty more force on the outer race and the tapers. SKF documents also mention this.

Tomorrow the bearings will come and I will do that. I practiced on the toasted bearing and it goes on easy. He also said you can heat it up a bit on the coffee maker, turning it for 5 mins, and put a bit of gear oil in the taper to assure no shock(not really necessary though).

He did say my current bearings are trashed, but would probably last a year or two.

 

[jd]

OK, Sure, I'm Cheap. But part of the reason I do so many projects myself is this: Why pay somebody to screw it up when I can be careful and maybe not screw it up. But if I do, I can fix it again on MY schedule, not negotiate with somebody else to correct it on THEIR schedule. Problem with that is: When I really need somebody, I have no experience to decide who'd be worth a try...

 

[96eb96]

I don't know..the first shop I took it to the guy made me wait 10 minutes to talk to him. His tech installed new calipers on a late 90s explorer and he was frantically calling around to find a new wheel. The tech didn't tighten them down right and the truck came in on flatbed with a cracked wheel and flat tire. That didn't instill too much confidence , but he probably would have pressed them in right, maybe using the outer race as the driver and I wouldn't even know.

You really have to trust techs when you turn over that key to them...

 

[96eb96]

Well they are installed now, a few taps got them in. Spins nice and smooth, added some gear oil till I install it. I needed a race driver to finish the job and finish with a countersink with the trashed race(I am selling the open diff to someone who wants to weld the gears, so he wants the bearing installed) so I would have had to buy an extra bearing anyway. Mr heat was only a few bucks.

The axle bearings go into the tube, they will be installed with the same driver. Doing brakes (parking, rotors, pads) while its out. For what I'm saving $10 isn't even a thought. Needed some extra parts so was able to bundle with rockauto the other day.

P.S. Those Harbor freight calipers are very accurate. I tested each measurement on the bearing per the manufactures spec and in the 10,000ths place there is a 5 or 0, always is within that tolerance. Some manufacturers differ in that position by a few anyway in their spec.