VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc transmission woes

This will be a long one.
1952 chev stock engine 3spd. Purchased with 85,000 miles on it. At 86,000 replaced the clutch pressure plate, and checked run out with a run out gage, pilot bearing good. The reason the transmission was pulled and the above work done was that the car was slipping out of high at 50/55 miles and hour on an UPHILL grade. At that time I replaced the Clutch gear bearing, mainsahft needle bearings, second gear thrust washer and the rear bushing, at the same time I installed an Oakie bushing in the toruque tube. The problem seemed repaired. At 96,000 the cluitch was slipping (long story not pertinent) replaced the package, checked pilot bearing. As I had the transmission out I replaced Rear bushing again, new second gear, new countergear,shaft and bushings, new thrust washers. Checked all other related parts. In about 500 miles on an extended trip it started popping out of high again, had to run the car about 150 miles before it happened. Next day same thing 100 to 150 miles popped out of high gear.Total for the trip 4 times. Always on a slight uphill grade. Got home replaced Indent springs with the later nos replacement springs. readjusted all linkage and had no trouble til yesterday, popped out after 125 miles of running did it a second time and then no more. Any thoughts here.

For what it's worth, I grew up with the Chevies of the late 40's and early 50's. I was always told not to ride down the road with your arm resting on the shift lever. This would cause undue wear on the synchronizer and eventually it would start to pop out of high gear. A couple of transmissions later I learned not to rest my arm on the shift lever. I haven't had the problem since. My older brother still drives a Pontiac and a Chevy from that era, still rests his arm on the shift lever, and his cars still pop out of high gear. He seems to think I don't know what I'm talking about and says the problem is caused by something other than his built in arm rest.

Of course, the problem could also be caused by linkage being out of adjustment.

If you have that habit of resting your arm on the shift lever while driving down the road it is at least worth considering.

In all cases I have seen the fit between the main drive gear and the high speed gear is the problem. The high speed gear fits into the splines in the drive gear to lock the output shaft to the input shaft. If the gears do not mesh completely they eventually begin to wear at an angle. Once the angle gets worn into both gears then they can be forced apart. It happens slowly as the and finally they come apart when the transmission is under load. Typically as you slow and have the transmission retard the speed the gears will begin to move apart. The more cycles the more movement until finally when under load they come apart.

If you rest you hand on the lever and start the gears toward unmeshing you have started the problem. The only solution is to replace both gears and then keep your hand off the lever (except when shifting). The detent springs can retard the problem but not eliminate it.

Is the 2nd & 3rd speed shifter yoke/fork OK. You don't have to remove the transmission to replace this item and they don't cost all that much. I think I probably have one if you need it.

That part looked pretty good when I had it apart but there was some wear. I did readjust the shift linkage as it was a little out of adjustment at the shift gate, have not had a chance to check it on the road yet but will by thursday. I will keep this in mind.

In mid-1953, GM installed two sets of needle bearings between the main drive gear that goes into the clutch and the tail shaft.
Make sure your pilot bearing is in good shape. Make sure your trans is bolted in solid to bell housing. Once you let it run out of line till it pops out of gear, you will need to replace the main drive gear, Syncro drum, and possible tailshaft as they have worn and will hop out of gear.
To avoid it popping out, let your foot off the gas every 50 miles or so when pulling that 100 mile up grade.

This was a common problem in 1949.....came back again in 1952 when they changed the motor/transmission mount design.In 1953 they changed the input to out put shaft set of rollers from one row to two to eleminate this problem.(started at the 1953 introduction)...After that the Chevrolet fix for the previous years was to install the 1953 shafts and rollers in the previous years if they had the problem.
Its even listed in the parts book after the main drive gear section ..."1953 main drive gear can be used in 1949-52 models to correct disengagement of high gear but requires use of 591851-591852 spacers,7450247 rollers, and 3699258 main shaft",,,,also use the original 14 rollers....
We had a lot of '52's with this problem when they were new and they could not cured unless the the above was done.Chevrolet also covered it under warranty for the first year or two.Check with your local dealer

One solution would be to find a 1953-54 transmission.The 1954 would be the most desireable as it has the roller bearing cluster gear.There is a 2 lug and 4 lug 1953 which makes finding some of the gears and sync. drum more difficult.

Gene, I have been told by a transmission rebuilder, that a four lug gear can be used by grinding two of the lugs off of a 4 lug gear. Anyone know of that modification being made?

Yes, that will make using a 4 lug on a 2 lug trans. possible.