VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 29 has 2nd gear problem

We are in the mountains of NC. The transmission will pop out of second gear when driving up a steep hill. Yesterday going up a steep road under maximum load I had to hold the shift lever forward to keep it in gear and twice the shift lever actually jumped forward towards the dash while I was holding it and then backwards into neutral. I rebuilt the transmission 600 miles ago and the 2nd. speed gears looked good. A friend has a 29 Chevy and he said he has to hold his in 2nd. on hills. Is this a common problem? What is the best solution?

Jumping out of gear is due to uneven wear on the gear teeth (or bushings or bearings). Once the gears have a taper (or can tilt on the shaft) they will move along the taper and eventually disengage. Holding in gear can eventually correct the misalignment but it might take several human lifetimes.

Thanks Chipper, I don't suppose new gears are available and I wouldn't want to try used ones. Would it be possible to turn the countershaft gear 180 degrees to put the opposite face to mate up with the sliding gear?

Hello Bare Feet,
There are 20 different reasons for popping out of gear after googling the topic. Everything from worn pilot bushing and every other bushing to worn shift linkages and forks to worn gear teeth to low trans oil, under load or during coasting and any other thing you can think of. The thing that is most in common appears to be the word worn. But, the issue is what is worn? Could it be just one item at fault or a combo of items? My only thought/suggestion would be if you take your transmission apart to inspect to see what may look different about 2nd gears teeth/bushing/play then that of 1st and 3rd. Also, because you need to hold second with the shifter, could shift fork be worn enough so as not to have full needed fork travel? Just guessing at all this, but would be interested to learn if you discover the cause.

Since space is limited in these old vehicles some people like to rest their hand on the shift knob while cruising in 3rd gear. Even the original service bulletins advised against that since it causes excessive wear. Could your trans be a victim of that even before you have owned it? At 6'2 and 210 pounds I was guilty of that myself. It is tough to remind yourself not to do it.

Thanks guys, When I rebuilt the transmission 600 miles ago I replaced all bushings and shafts, and the sliding gears, however, the 2nd. gear looked ok so I left it. I have ordered a NOS one from GW. so I will see if that helps. The shifting mechanism was worn and required some welding to correct it. I'm not looking forward to the job, but may get to it this winter. I'll let you know if I find the problem.

Update.
The intermediate gear has two chipped teeth right where the bevel is. I bought a new gear from Gary Wallace, however, it turned out to be a 1928. It is almost the same except the teeth are not cut as deep as the 29 so it binds. Gary does not have any 1929 gears (they are also for 30 and 31). I'm looking for help finding a gear part number 590469 It's the middle gear on the countershaft (2nd speed). Or an alternative would be to find a shop that could cut the teeth down on the 1928 gear.
I can also post this in the parts wanted.

The Filling Station is sending me a set of used gears. Hopefully this will work.

There is a difference in some of the gears. The main shaft in a true '29 transmission has 10 splines, whereas the main shaft in a '25, '26', '27, '28, '30' and '31 are 6 spline. You can take ALL of the internal parts out of one case and put them into another year case but certain gears will not interchange. If some PO changed the main shaft, or quite possibly the whole transmission you still may not have the right parts. Of course the '31 case will mount to the clutch cover in a different pattern from all previous years.

Most years had a code cast into the case. Not all of the '29 cases were marked or even dated. I have some that just have a stamped serial number starting with an "A" on the top near the shifting cover.

One last crazy thought is that when you have everything disassembled to take your pilot shaft and stick it up into the back of the engine. Temporarily mount your clutch cover and measure all around the distance between the shaft and the hole in the cover. They should be concentric, or really close. Some rebuild shops have not known to use the clutch cover as the centering point of the rear main bearings when align boring these old engines. One other member measured his and it was 1/8" out. I think he dug through his stash of cast bell housings and found a combination that was much closer.

Please let the forum know everything you find. I can guarantee there are other people who are experiencing the same problems.

Hi beachbum

With respect, there is only one way to accurately measure bell housing run-out or concentricity.
It does not involve a transmission shaft.
A dial indicator/gauge must be mounted to the rear end of the crankshaft with the point resting on the inside edge of the hole in the installed bell housing the transmission mounts to.
The crankshaft is then rotated and the run-out read on the gauge and compared to the maximum allowable spec.
No other method will give an accurate indication.

The parts price list book lists all of the countershaft gears and the reverse idler gear as correct for 29, 30 and 31. They do not have splines. The intermediate gear that Gary sent me has 1/4" long teeth whereas my 29 gear has 5/16" long teeth, other than that they appear identical so he said it is probably for 1928. I may check concentricity of the clutch in relation to the pilot bushing but the parts appear to be in good shape. I did have to get a new countershaft fabricated because metal chips from the damaged intermediate gear gouged the one I had bought from Billy Possum and also the bushings.
The transmission case has number 590391 and an F below it and the Transmission cover is 590281 with a C5 in the surface like it was stamped but probably just cast.

You are right, a dial indicator is the best and most accurate way of measuring concentricity. But not everyone has one or access to one. With the pilot shaft inserted you can get pretty close and determine if you have a problem with a vernier caliper or even a machinists scale - which most people have, or can easily get. On these old low tech engines I suspect anything under about .020" probably would not be much of a problem. The clutch splines probably have close to that amount of play.

The last '29 engine I checked, it was really difficult getting the dial indicator mounted on the crankshaft in a position to even get close to determining if it was align bored properly. I did not expect a problem with it because I was pretty sure I knew who had performed the boring and he would know the procedure. So checking it was just more of a confirmation.

Hi beachbum

Again respectfully...
You are right that there will be a lot of play in the clutch splines, and some in the pilot bearing as well.
And that is precisely the problem.

While I don't have the Chevrolet specification at hand, I would consider .020" to be a HUGE alignment issue.
And I would expect trouble with far less than that.

My engine was professionally rebuilt and sent out for line boring, so I am hoping it is within tolerance.
I would think that if the line boring was off center the input shaft would go into the main transmission bearing at a slight angle and also would be at a slight angle in the pilot bushing. I can see where the clutch splines would be affected.

On a more modern engine .020" WOULD be a huge problem. The point is that an owner needs to bring the cast bell housing AND the stamped clutch cover to the people performing the line boring. They have a pretty good idea where the front bearing should be to get the proper backlash with the cam gear. On more modern engines the rear main bearing IS centered. On these older engines that may not be the case. The bearings had enough material it could be machined to allow for variances in casting and imprecise machining practices. Without the parts that will be used with that particular engine they will center the rear line bore on the bearing itself. The service manual is quite specific in their comments about it being centered on the bell housing. Without taking those parts in and stressing to the shop that they be used as a reference, it will be a crap shoot if it will be correctly bored to line up with the transmission.

In a previous thread a fellow member said he found his to be off by almost 1/8" or .125" I think it was a running car. If no one actually checked, .020" may not even be noticed. I think he dug around in his parts and found a set that was closer. That is how much variance there can be in those parts.

Oh well, don't worry about it. It's just an old car. It'll be fine.