I am just working on reassembling a diff that has had the roller thrust bearings used in it. we have been having discussions on what the end float of the diff carrier should be when using these bearings. Should we run with a tighter clearance than when using bronze thrust washers?
Since it's not too late... go with the bronze thrust washers.It's hard to get flat rollers to roll in a circle and I've seen wear and pitting on the one's I've removed. The Bronze washers are more forgiving and will last for a long time. If your determined to run the roller thrust bearings, then don't run any pre-load on them, .005 - .010 should be OK.
Put the roller thrust bearings in and bolt the carrier up and go. I have a half set in mine that my friend changed out before going on the Alaska trip in 01 that had over 40k on them then. He had used those with his ruxtel, I added a new set for the other side and since have put another 40k on both. Nary a problem, they are used in all automatic transmissions which carry lots more thrust loads at high temps. KGB
The little rollers on the "roller thrust washers" are cylindrical... A cylinder rolls straight ahead, not in a circle, therefore if the cylindrical rollers are forced to roll in a circle, then most of the roller is being dragged along. If somebody would make a very large mock-up of one of these, maybe about 5' in diameter with 2" diameter rollers 12" long, the drag from the rollers would probably be so great it wouldn't turn.
The stock hardened steel washers and bronze thrust washers work on the same principle as the bearings in the engine. They are engineered to form a fluid film when turning. From data I have collected they should provide satisfactory service for over 20,000 miles if the axle was properly overhauled and maintained.
I should also point out that engine oil leaking down the drive shaft tube into the rear end does "contaminate" the rear axle lubricant and will significantly reduce the longevity of any rear axle overhaul. So will use of incorrect lubrication, but I won't open that can of worms!
And for those that don't know, Ruckstell axles have a large ball thrust bearing on the ring gear (left) side which is the side that gets most all the load. Whatever you choose to use for thrust on the right side will probably last you a lifetime no matter what you put there!
In the early accessory parts books there was ball and roller thrust bearings. Just a trivia note the ball thrust bearings in the pinion housing are the same as the early front ball wheel bearings. It was learned from a source that the early front ball bearing assemblies were also used on some early Massey combines. I was fortunate to find a pair of complete ball bearing assemblies through a "T" vendor, they are now increasingly difficult to find (complete assemblies).
David, I just sold a NOS set thru the classifieds a couple weeks ago!
I know many people have used the roller bearing thrust washers and their thousands of miles of trouble free driving may be a good indicator that they are okay.
But I prefer the hundreds of billions of total miles run by fifteen million other model Ts. Babbitt washers have failed because Babbitt it inherently brittle and suffers heavily from acid erosion due to very small amount of water contamination.
To my knowledge, and probably close to a very rare "absolute", NO brass/bronze thrust washer has ever failed without a serious outside cause (such as total lack of lubrication or broken gear carrier).
And for the few roller bearing thrust washers I have known of used in T rear ends? I have known of several that have failed. Not a good average.
Do as you wish. Follow the advice of whomever you want. But I will probably never use the modern roller bearings in that application. Yes, I know that they are used in modern automatic transmissions. The application is different. The lubrication is different. Frankly, the stresses are different. What should work in theory may not work in the real world. I like the odds better for the brass/bronze washers.
Drive carefully, and enjoy, W2
I think it is Royce who has a saying something to the effect of 'It's a solution to a non-existent problem'. I think roller thrust washers fit into that category.
Well put Wayne Sheldon they were an after market accessory to make something better that didn't need to be any better. There is added risk of foreign parts contamination ie unwanted bearing parts in the housing. There isn't enough side thrust to warrant anything other than the bronze washers. The engineers of the day had a pretty good idea of what worked and what didn't.
Yes, I know some folks have used the roller bearings with no trouble. (Just like fiber timing gears.) But I see them as the superfluous introduction of complication that increases the odds of failure. I expect even if I drive my T until I'm 120, the bronze thrust washers will outlast me.
Has been working in the real world for over 80 thousand miles. No trouble to set up, how many are using modern pinion bearing and axle bearings and dizzys? But are so negative about something you have never tried. KGB
I have no dog in this fight, but the Torrington roller thrust washers have been used in millions of automatic transmissions for decades. I agree that brass washers are best for T differentials, due to the amount of surface area. -Ed
I have taken 3 rear ends apart that had roller and ball bearing thrusts in them all three were a mess.
I imagine babbit was used at the factory to save time. They did not check any clearance or pre-load, the just bolted the things together and turned the rear end with a big electric motor and let the babbit thrusts adjust themselves.
If I were putting a rear end together with roller or ball bearing thrusts I certainly would NOT leave any clearance. I would make them snug and a little drag would not hurt.
The rear housings expand when hot, like any rear end. Ball and roller bearings don't need clearance.
Front wheel bearings need pre-load, differentials with roller bearing carriers need pre-load.
I'd be interested to hear what the advantage is suppose to be. Less friction? How much friction is in there now? How much with the roller thrust bearing? How does that translate into HP? Top speed? Acceleration? Will I notice this in practical driving or do I need a dyno that reads 3 decimal places to see it?
I didn't go back and count, but seems like there were 4 or more known cases of roller thrust bearing failure noted in this thread alone. How many bronze thrust washer failures in T rear ends does anyone know of? I see little to no advantage and a greater potential for failure, backed up by the experience of others. That is plenty reason for me not to try them.
Someone told me that some of the Montana 500 cars used them with the idea that they reduce friction... But I would imagine that everything in those cars gets torn down, inspected, rebuilt and replaced before being raced again... WONDER if they are one of those "race car parts" that gets replaced after just about every race!