Melting Babbit Part II

[29FordRoadster]

Back in May, 2012, I wrote about the babbit melting in my rear main. I am sorry for the delay in reporting what we think was the problem. What we think was the problem was that the replacement input shaft we in stalled in the transmission was about one quarter inch longer than the one we removed. The longer portion was the end shaft that the pilot bearing rides on. This put extra pressure on the rear main and caused difficulty in shigfting gears as well as melting the babbit we think. Our solution was grinding about one quarter inch off the end of the shaft. I have only driven the car about 100 miles since the repair but the shifting is greatly improved. We replaced the two piece modern rear main seal and I still have some leaking from the rear main, but nothing like before. My thanks to Mr. Kohnke and Mr. Jim Brierly for their suggestions in my earlier posts. Wayne "29fordroadster"

 

[ivoryjohn]

I too am going through the same thing with a slight twist. In November-December Of last year I had a new rebuilt engine installed. It has a lightened flywheel, V-8 clutch, touring grind on the cam, 5.1 Snyder head and a "B" carb. The engine runs real well. Within 500 hundred miles it rained oil under the car, I had not gone above 40 mph during the break-in, and it left dinner plate sized pools of oil every time I stopped and dribbled a snail trail for good measure.

At 750 miles the engine was pulled and the inspection proved there was a two piece modern wick rear main seal that did not work and the slinger had been turned down to allow the installation of the wick seal. The crank was sent back to the machine shop and the rest of the slinger was turned off and a modern neoprine rear seal was installed. The thrust bearing in the flywheel had failed and the shaft of the transmission was ruined. The transmission was rebuilt with a new repo shaft and new fly wheel bearing. It was reassembled and I went on my merry way.

Almost immediately the leak was back but slightly improved. I drove the car with the new neoprine slinger 2600 more miles for a total of 3600 on the engine before I could get it back into the shop to see why it was still pouring oil. I would have had it back in the shop a lot sooner but there was no room on the schedule to get it in for the work.

It was discovered that I have in excess of .40 thrust on the crank and the rear main is starting to melt quite a bit. I don't ride the clutch and wonder if perhaps I may be suffering from the same problem you did with a transmission shaft causing pressure on the crank as you describe. Is there a way to measure thrust play with the engine assembled such as measuring between the front crank pulley and the engine block while running or at rest. What else can cause thrust play and rear mains to melt besides transmission shafts and clutch pressure? Could turning the slinger off allow the shaft to run forward and aft?

My hopes were that spending the money on a new engine would give me a strong, long running, dependable touring engine I could drive safely. Can I still have that with a repaired rear main and not sending the engine back to be repoured and rebuilt?

I would love to see both of your posts on the same page to map the history of your problem and solution.

Thanks for the update!

 

[Jim Brierley]

Thanks for the update.

 

[Kohnke Rebabbitting]

Is there a way to measure thrust play with the engine assembled such as measuring between the front crank pulley and the engine block while running or at rest. What else can cause thrust play and rear mains to melt besides transmission shafts and clutch pressure? Could turning the slinger off allow the shaft to run forward and aft?


If you are not sure if there isn't something holding the crank to go to the rear for measurement of the end play, just make sure all the play is out of the rear thrust, and see what you have for thrust on the front side, it will come out the same. We set to .003, and never over .004. We also hand scrape the fit, as there is no align bore that will do it perfect.

The seal area will have nothing to do with the thrust.

Normally, you could get a measurement off the front pulley, but if you do have something holding the crank from going all the way back, it wouldn't be a good measurement. So the most sure way, and most accurate is pulling the pan, and measure the front side of the thrust.

If you would have over .006 play, it should be fixed. If you could get over .006 at the front pulley, maybe that would tell you enough.

Herm.

 

[J Franklin]

Maybe checking to see if a newly purchased input shaft fits the pilot bearing without bottoming out would be to test fit it before it goes into the transmission. I had a problem once with a pilot bearing not fully seated in the flywheel, and lost the thrust.