Ring gear fit to carriage

Bill Goddard

Bill Goddard

Well-known member
I have a rear end ring gear that will not drop over the mounting diameter on the carriage casting that holds the spider gears. The ring I.D.is about 4.125" dia and the carriage is w/in .001" of that dia. I have tried heating the ring in an oven and it did drop on but I ran out of time fooling with the 9 bolts. It seems there is only one way the ring will go on and I haven't found it yet. I will try the heat method again tomorrow but I was wondering if I could have a machine shop trim a little off the carriage O.D. to allow assy and fitting of bolts at room temp. I have been told the ring should drop into place and it doesn't. Any thoughts from the experts out there? Thanks Bill G
 
I have encountered this a time or two in the oast. Like you said, usually putting it in the lathe and making a light cut will take care of it. I would be careful about too much heat and you really want a couple thousandths of clearance where the ring gear will rotate on the carriage.

BTW, who made the Ring &Pinion, ...American made or off-shore??

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I have seen some that were tight but I never had to resort to heat or machining. You may have a burr on the outer edge of the carrier holding the ring gear off. Run a file around the lip of the carrier. I have had a few where I started all the bolts into the holes then pressed it on with a shop press. Once down over the edge, I could usually rotate it.

If you are installing a repo ring & pinion check that the pinion gear sleeve diameter has two different dimensions or you will have fits trying to set the pinion bearing pre-load. You can feel it with your thumb nail where the two dimensions come together in the middle of the sleeve. The area close to the gear should be .0015 larger in diameter.

The R&P sets that come from Snyder and Bratton are machined this way. However I have found on occasion the manufacturer did not hold the tolorances correctly and I had to have a slight amount machined off the back end of the sleeve.

You want the bearing closest to the gear to go on with an interference press fit. You want the second bearing to be slightly more than a snug fit. When you go to press the first bearing on if you feel and hear that crunching sound indicative of press fit at the back end of the sleeve, stop and remove the bearing and have that end of the sleeve machined.

Tom Endy
 
Tom - I will try the file treatment next. Also, the pinion has the 2 different dias.

Brent - The ring gear was given to me and is brand new and likely a repo. I don't know its history. The pinion is older and used but in excellent shape. I am sure it is original. I know they are supposed to be matched but I have read so much conflicting information about the subject I have decided it is probably more important to set the gear clearances properly in the first place.
 
I have heard the story about the ring & pinion being a matched set for all the years I have been fooling with Model A's. I don't believe they came from the factory matched. They became matched as they ran in the car and piled up miles.

Most of the original R&P's I have seen have a number stamped into the end of the pinion gear. When the flat side of the ring gear is bead blasted usually there is a number found that has been scribed there by hand that matches the pinion number. It is sometimes difficult to see, you have to have the ring really clean and hold it at an angle to the light to see it. I have seen this so often that it must have been a practice at the factory when the differential was assembled. The worker apparently took the two parts from stock separately and scribed the pinion number on the ring. Reproduction R&P's usually have matching numbers already stamped on both parts.

You may be able to get away with a new ring and an old pinion, but I believe it will be noisy. It will no doubt quiet down some as the two parts wear in.

I always check for matching numbers on a used R&P. A while back I had a very good looking R&P I picked up at a swap meet. They were wired together when I found them. I could not find a number on either. When I had the differential fully assembled it was extremely noisy just cranking it over with a socket wrench. I couln't give it to the customer this way. I had to tear it back down and discard the R&P and replace it with another.

Tom Endy
 
Tom - I put the carriage half in the lathe and shaved .001"-.002" off the mounting dia and the ring fits fine. I got all the bolts in and tightened up to 30-35ft lbs like in your write-up. I assembled the axel housings w/out gaskets and the ring gear is stuck tight and won't turn. So far so good. Tomorrow I will disassemble and add gaskets to pumpkin to set the axel bearing loads.
 
Bill, I'm glad it worked out. The thing that I think so many people just do not realize is the amount of time it takes to make many new reproduction parts work correctly. It is definitely easier to re-install a worn used part and call it "good enuf!"

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