MTFCA Forum

I recently drove my 1927 coupe for the first time since restoration. I drove 10 miles.

After getting back to the garage, I looked it over. I touched the rear axle pumpkin and found that it was very, very hot. If I had tried to keep my fingers on it, I believe they would have been burnt.

I had the axle rebuilt, including new ring and pinion, rear axle sleeves (hardened), differential thrust washers(brass), differential thrust plates(steel), thrust plate pins, differential ring shims, rear axle shim, full floating rear hubs, modern pinion bearing, Sure-Stop disc brakes, and one rear axle shaft(1/16" longer length). There is grease in the axle.

Has anyone experienced this?

I am experiencing the same in my 1920 roadster. I rebuilt it and I have shims with the thrust washers and I think it is too tight. It turns ok and I ran the rear end on Jack stands and it didn’t heat up but with the weight of the car on it it gets pretty warm. I am about to take it apart and I will let you know what I find.

Bruce,


When you state there's "grease" in the rear end you don't actually mean grease do you? Like grease that comes from a grease gun? There should be gear lube in there. Like 600w sold by the suppliers or maybe even 140 gear lube as sold at auto parts stores. Essentially very thick oil. Hopefully, that's what you meant.

Its too tight.
Weather from not enough clearances built it during the rebuild (should have been checked @ each sub assembly) to a steel thrust washer that fell from alignment on it's pins during assembly or too tight a gear mesh. All things that should have been caught with the axle assembly spun before installation & before the outer grease seals are installed.

I can only think of two things which would cause this. something too tight or exhaust muffler outlet too close to axle. As stated above, could be thrust washer off the two pins. Also if the oil it too thick it could possibly cause this. 600W is OK in a standard rear axle, but you need 120 or 140 in a Ruckstell. because it has to get inside the inner planetary cage it needs to be thinner. The gear mesh could even be too tight. Anything too tight could cause it.
Norm

It has 600W lub.

Oil filled to the plug? or the mistake of 1-1/2" down like what is recommended for early diffs?

Do the wheels turn freely?
Sometimes a roller bearing is tight. Often from the sleeve not seating right on the pins that locate them.
Just one idea.
I had an outer one that heated the axle enough to the point that it broke.
Rich

Rich I think that’s a bingo

According to the rux build book 90 wt is preferred. 140 for a stock rear end. Not confident the thicker lube will get into the rux inners. I have always used 90 wt. Not had an issue lubricating. MHO. When I fill the rux for the first time, I try to squirt oil into the carrier bell thru the outer slots.

You're correct. 90 it is. I should have consulted the manual. I have Ruckstells in all of my T's.
Norm

From Lang's

When I checked the diff lube on Henrietta before returning her to the road following her 52 year long hibernation , I could not detect a particular level of lubricant. Rather it appeared to be grease filled. I put the plug back in and have now used the car for 6 years of local and t tour driving. When It fails to proceed due to a rear axle problem, it will be interesting to see what is really in there.

Allan from down under.

Bruce,

I think it's most likely that your thrust washers are set up too tight. You may be able to increase the clearance enough by parting the 2 halves of the housing and sneaking in another differential case gasket. If done carefully, it may not require removing the rear end to do it. I believe the gaskets are about .005 thick. Even if you already have a gasket in there, adding a second shouldn't be a problem. I would not add a third however.

When fitting the thrust washers, I do not use a gasket between the 2 axle housings. If I get a good fit that way, I then use sealant only. If it's just a bit too snug, I add in a gasket, (and sealant too).

So how tight is too tight when assembling axle halves? Lots of good ideas here but let’s have greasy finger data. I just put one together. Assembled with just some light grease to hold it all together. First attempt it locked up, and by the fifth or so attempt gently sanding the bronze washers on a plate of glass it rotates with light resistance with a finger through the pinion opening. And that’s with all the bearings and seals installed. I can reach in with a slimy finger and after it moves its moves freely. And with a dial indicator at one end and a jack pushing up under the other axle in the vertical position it has no endplay.

End play can also be within the differential case between the axles. That also needs the washer to be snug.

David Mazza wrote: ↑

Mon Sep 18, 2023 4:01 pm

So how tight is too tight when assembling axle halves? Lots of good ideas here but let’s have greasy finger data. I just put one together. Assembled with just some light grease to hold it all together. First attempt it locked up, and by the fifth or so attempt gently sanding the bronze washers on a plate of glass it rotates with light resistance with a finger through the pinion opening. And that’s with all the bearings and seals installed. I can reach in with a slimy finger and after it moves its moves freely. And with a dial indicator at one end and a jack pushing up under the other axle in the vertical position it has no endplay.

David,

It would appear that you got it "just right". I think .005" clearance would be just about ideal. The idea is to get the bronze washer on the ring gear side adjusted just right for a good gear mesh. The opposite bronze is then dressed down to achieve the proper clearance.

David Mazza wrote: ↑

Mon Sep 18, 2023 4:01 pm

So how tight is too tight when assembling axle halves? Lots of good ideas here but let’s have greasy finger data. I just put one together. Assembled with just some light grease to hold it all together. First attempt it locked up, and by the fifth or so attempt gently sanding the bronze washers on a plate of glass it rotates with light resistance with a finger through the pinion opening. And that’s with all the bearings and seals installed. I can reach in with a slimy finger and after it moves its moves freely. And with a dial indicator at one end and a jack pushing up under the other axle in the vertical position it has no endplay.

As described - Too tight.

Grease will add more friction & skew the finger test.
Grease can fill the lube cuts in the bronze thrust washer & keep the gear lube from migrating where it has to go. I use motor oil.
Every clearance should be .005. Tighter between the axles is ok.(fiber washer or equivalent)
There should be no resistance. If you do have, its too tight or something is bent.
If you have to use a hammer to get the Hyatt bearings in - too tight You should be able to twist them in.
After complete assembly, you should be able to easily turn the U-joint with 2 fingers.
Outer seals are going to create friction. They go on last.
Your last test, vertical with no end play - Too tight.

Recommendations?

As Jerry O suggested. Try adding one gasket between the housings.(if its a tight between the housings situation)
If its a tight gear mesh, you can also add a shim or 2 to the spool face. If you loosen the spool bolts & the D/S gets easy to turn, its a tight gear mesh.
You will need to lower/remove far enough to get to the U-joint to turn by hand.
Put the proper 90wt oil in.
If any or all the above dont get the parts turning free, tear it down & reassemble more carefully with the proper clearances @ EVERY step.

I do not have the experience, etc. to insert a gasket between the two housings as Jerry has described.

From comments received, it appears the consensus is that my very, very hot axle pumpkin is due to either a thrust washer that has come off of the pins or the proper clearances of various items were not achieved during reassembly.

I assume there is nothing more I can do to try and determine exactly what is the problem is.

Bruce - can you not speak to the person who did the initial work for you ?

Hi Bruce,
Do you have or know someone with a infared thermometer? That may help figure out where the issue is. Should not be that hot. If the rear
whines the gears are to tight, if the thrust are to tight the heat should show @ the pumpkin, if the bearings are to tight it should show @ the
bearing. if it got that hot in 10 miles the issue should show up in 5 miles & not transfur to other spots. Good Luck.
Craig.

Steve, Yes, but I wanted to know if others had experienced a very hot pumpkin and what others thought might be causing it.

Hi Bruce,
I'm going to go out on a limb with you are not happy with his answer? If you payed for the rear end ask & confirm the warranty. If a friend did
it for you then you may have pissed either or both of them off. Either way I have not had that much heat in a rear end unless it was well over
100 degrees out. I have only built about a dozen T rear ends but can not imagine that if a steel thrust slipped out of place you could even turn
the rear end by hand let alone bolt it together with out screwing up the housings.
Craig.

Craig, I have no experience with rear axle rebuild, but I had the same thought as you regarding a thrust washer slipping out of place.

Bruce

If the emergency brake pads were dragging on the drums and the disc brake calibers were dragging on the rotors, I assume this additional load on the pumpkin gears would not cause the pumpkin to get very, very hot. Am I correct?

If the brakes were dragging sufficiently to heat up the rear end, you would have also noticed the car's power & speed being dragged down significantly.