I have never seen a thrust face perfectly smooth. I almost think the circular marks are from factory machine work. I'd put a Cluster gear in and see if it comes into spec with a thrust washer. If it did I'd run it. Thrust washers come in different thickness to take up ware.
I have several that are perfectly smooth. If you want to know the actual distance front to rear you can get that measurement from the Mac Van Pelt early trans. book.
If that surface is as rough as it looks then it could cause premature wear on whatever you put there.
The thrust washer that belongs there is not supposed to rotate at all. If your washer lock tab is correct along with proper thrust gap you won't have a problem, at least I haven't yet. When your gear box is severally worn and thrust goes past the lock tab length you should already know you need to give it some attention.
Check how worn it is and if it’s within tolerance . it does not look that bad , other then the swirl marks is the area flat ? Or worn wavy ? worst case you can get the area built up and machined flat again . if it’s close to spec can you shim to tolerance ?
There’s a little bit of confusing information given out on this issue. From what I can see in the picture, there’s definitely some circular wear on the thrust surface in that gearbox casting. It’s hard to know how much casting has been worn away. Forgetting the look of the wear for a second, you can throw the countershaft back in along with the matching thrust washers (new, unworn washers) and measure the clearance. Shove the cluster gear forward and put a feeler gauge behind the rear washer (fitted between the washer and the thrust face of the gearbox). The acceptable factory spec is 0.005 to 0.015” of clearance. The early gears (32-35) used a rear washer that was identical to the front washer (B-7119) which has a tang that fits in the slot cut into the gearbox casting thrust surface. A second washer fits into a recess in the small end of the cluster gear. In this instance, the rear washer with the tang is stationary and the washer fitted to the recess in the gear spins with the gear against it. The next generation of gears (36-48) used a single thick rear thrust washer at the back of the cluster gear. It’s got the 4 nubs that engage 4 slots in the rear of the gear. This arrangement means that the rear washer is spinning against the rear of the gearbox casting all the time. Thus, it tends to wear away the casting, resulting in the circular grooves seen in the photo in this thread. The next version (1948-54) uses the two part thrust washer design at the back of the cluster gear…..the gear has two protruding nubs that engage a thick thrust washer with a big bow tie shaped opening. A second thin washer is fitted between the thick one and the back inside face of the gear box. The thin washer is not locked to anything….it simply fits in the space and can rotate or stay still. Regardless of which design is used, all three versions would be checked for the same end play clearance as mentioned above. The setup that does not constantly spin against the gearbox thrust surface will provide the best longevity and least damage. However, you have to work with the cluster gear you have available and that really drives the choice of thrust washers. You can buy more years of use if the transmission is totally cleaned and fresh gear oil is used. The accumulated metallic grit is what does the damage. If the surface damage is not too much, and the clearance is within spec I’d be comfortable just replacing the thrust washers front and rear. If the rear surface is worn back too much, yet is still somewhat smooth, you could try fitting a steel shim washer against the rear of the case.
Thank you everyone! I need to get an order into Mac for some washers etc. My gear set has the two prongs.
I bought 2 books many years ago so I could keep a Clean one in the Office and one on my bench while building a gear box. The one on the bench is all marked up from oily fingers and a lot of it is hard to read hence the Clean one in the Office.
I machined a trepan groove in a Mopar 727 to accommodate a Torrington style bearing. It was a specialized enclosed needle bearing so the rollers don’t make contact with the drum or the housing. This was tricky but it worked really well. Maybe there’s a bearing application that would work for the toploader(?)
The problem with a NO NO, is that you fail to offer the why with it. No offense Jimvette59, but can you explain why NO NO to the curious types? I honestly don't know if it would work or be suitable, but it was a step up from a NO NO as far as suggestions go. And now seeing that Adriatic Machine was thinking outside the narrow mind of NO NO, he's accomplished something. That's brilliant! I liked it for just that reason. Forget it also supports my suggestion but hey...It was a great idea he had. But as far as it goes, I can also think of a few other solutions to that problem, suitable for us poor broke and under funded. Some I'm sure would be more successful then others as a repair solution to a worn surface, but still, trying something is better then a NO NO leave it to die because it's broken. I agree. And thanks for that information you posted. That said, a modern transmission and the use of those needle bearings solves that. As your post mentions model year improvements, maybe when a guy has it taken this far apart they might think enough to see the small improvements that led to the larger ones.
Thank you for the mention Noel but I can only take credit for the machine work, not the R&D. This was for a friend of mine who races Hemi muscle cars and owns a transmission shop.
Well if I hadn't taken apart a OT FWD transmission just to 1) see if I could, 2) see what's inside, 3) how far I'd have to spread it out to possibly think I could put it back together in the order it came apart I wouldn't have deemed it possible because up until then I had no clue they existed. Not all R&D is a success, Seems I never did put the transmission back together, but, I did see some cool transmission guts and gore, salvaged some art project parts, some isn't that cool stuff. Success thru failure usually leads to improvements. Of course, whenever someone says something that doesn't fit the normal, first thing is the no no response. But that bearing to me was a solution to a problem and being an improvement, should also be seen as the bonus to doing so. So while I'm going to say it was a great idea, the hero is you for making it real.
So here we are talking about a Gear Box that is 74 years old at the very least not counting the F-1 series Truck unit. I often wonder if the unit I'm working on has ever been taken apart prior to what I'm doing and quite sure many have never had the lid off them. How many miles of normal driving does it take to wear one out? If you do the Best rebuild you can and set the end play up correctly, will it ever get back to where it was when you found the Thrust washer surface to be an issue. I would love to say I'm going to drive my Flathead powered Roadster 60K miles in the next 10 years and wear the Gear Box out again. With all the other toys I have to drive I doubt that will happen. Add to that in 10 years I'll be 87 so I doubt I'd be the one to be doing the overhaul the next time. That given I'll just continue to clean up the marred thrust surface the best I can and install new thrust washers against it and make sure the tolerance is tight. Why would I mess with success?
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