52 M37 transission

[BobO]

My nephews M37 has had the problem of grinding when shifting up to 3rd gear. I am in the tear down mode in search of the common snap ring problem. I have about half torn into it. I am at the part in the power train manual where it says to Drive reverse shifter fork shaft to the rear with a bronze drift and hammer. This thing don't want to budge. I wonder if a couple sizes bigger hammer is the answer or that might break something? I have got the 410308 seal and 99212 Redi Sleeve and plan to use 50w syntethic engine oil.
Any help with this and other tranny pointers are greatly appreciated.
Thank you
Bob McFail

[Gordon Maney]

Charles Talbert to the white courtesy phone....

Charles should be along shortly with competent advice.

[Charles Talbert]

2 different types of reverse idler gear shafts were used. If your shaft has a threaded hole in the end of it, clear the hole of any debris, simply thread a bolt in the hole until it bottoms out, use a slide hammer puller on it and remove it that way. If yours doesn't have the threaded hole, you will have to go in through the front of the case after the mainshaft and pilot shaft are removed. Go in with a long bar, (approx .750" diameter) that will reach the inner end of the shaft you are trying to remove. It will be on an angle, so be careful to place the bar only against the end of the shaft, from outside the case hit the bar with a 2# hammer and drive it out. After it moves an inch or so, you have driven the press fit out of the case and it can then be pulled out easily by hand. Be sure no hammer blows are delivered to the cast iron case, as long as you don't hit the case, you should have no problem. I've never had one that offered any real issues with removing this shaft.

I'm assuming you are going through the entire unit while you are into it, however if you are only looking for the snap ring issue that affects 3rd gear; that is on the front end of the main shaft. Many times the snap ring groove on the shaft will be broken off letting the ring ride forward instead of the ring itself being broken.

[BobO]

Hi Charles,
My intentions are to just correct the 3rd gear grind snap ring issue. I see the shaft is the blunt type no threads for a bolt. I have the input shaft removed. The companion flange is removed from the back end. I wonder now does this reverse shifter fork shaft have to be removed to get the main shaft out and check the snap ring issue? I appreciate what you have shared with me on this matter.
Bob McFail

Thank you Gordon for your assistance.

[Charles Talbert]

Hi Charles,
My intentions are to just correct the 3rd gear grind snap ring issue. I see the shaft is the blunt type no threads for a bolt. I have the input shaft removed. The companion flange is removed from the back end. I wonder now does this reverse shifter fork shaft have to be removed to get the main shaft out and check the snap ring issue? I appreciate what you have shared with me on this matter.
Bob McFail

Thank you Gordon for your assistance.

I apologize, I was thinking the reverse idler shaft instead of the reverse fork shaft in my earlier post. I was busy with something else this afternoon, and didn't read carefully enough to get a clear understanding of where you were.

Yes the reverse fork will need to come out ahead of the main shaft. The rear bearing retainer also stops the fork shaft from sliding out the rear of the case, you need to remove the yoke and bearing retainer, then proceed to drive out the fork shaft. It will only come out the rear because of the way it's machined. Once the fork shaft and fork is out, slide the entire main shaft assembly back far enough to get the ball bearing out of the case and remove it from the shaft with a suitable jaw puller. Once the bearing is off the shaft, raise the front end of the main shaft upward lifting the whole main shaft assembly out through the open top. You can then proceed to disassemble the synchronizer, hub, 3rd gear and bushing, then 2nd gear from the shaft. The 1 snap ring holds it all in place in the early trans. If the ring is still in its groove, check the synchronizer hub for end play before removing the ring. If there is any movement at all, it's too much and a thicker ring will need to be installed to eliminate it. If you find the ring out of its groove, a broken ring, or a broken groove, then you are facing a full main shaft assembly rebuild. Be sure to check every tolerance very carefully along the way, remembering that the ring just doesn't pop out for no reason. There is some issue in play that caused it that will need to be corrected. Simply putting the ring back in place and reassembling the unit is doing nothing more than fooling yourself. You must locate the trouble spot and correct it in order to get a fix that will last.

A grinding issue when shifting into 3rd could also be a synchronizer problem that would require replacement of those related parts, but it is more likely to be the snap ring off for some reason.

Feel free to ask further questions if you need too. Now that I'm getting a clear picture of where you are with this, I can talk you through whatever procedure you may need help with.

[BobO]

Charles, I thing I will change my tune and do the complete tear down and rebuild. Thank you for sharing this information with me and I also appreciate your other posts I have read which has helped alot restoring this truck.

Bob McFail

[BobO]

3rd gear grind

I am rebuilding the gear box. The main shaft had the snap ring right in place with no tolerance. The gear to gear tolerances were right .011. I inspected the sycro assembly parts. The 6 pins are in place and I find no obvious wear. I found small shavings in the bottom and no sludge. No broken off parts. The main shaft pilot bearing is the only part that looked bad. One of the parts vendors sent me a replacement with a bad fit 15 rollers instead of 19 and it would not go on the main shaft because it is 1/8 inch too small of a bore. It is the correct 1 1/2 long and good fit in the input shaft though. On the reassembly test according to the tech manual there was .170 clearance between 3rd gear and the outer syncro which calls for .040 and .100 tolerance. There were 3 shims at the rear of the main shaft. I bought 5 more shims to close the gap. This would take the slop out of the sycro assembly. My question is does this sould like I am rebuilding this right? Are there others receiving a main shaft pilot bearing with incorrect inner bore size?
Thank you
Bob McFail

[Charles Talbert]

I am rebuilding the gear box. The main shaft had the snap ring right in place with no tolerance. The gear to gear tolerances were right .011. I inspected the sycro assembly parts. The 6 pins are in place and I find no obvious wear. I found small shavings in the bottom and no sludge. No broken off parts. The main shaft pilot bearing is the only part that looked bad. One of the parts vendors sent me a replacement with a bad fit 15 rollers instead of 19 and it would not go on the main shaft because it is 1/8 inch too small of a bore. It is the correct 1 1/2 long and good fit in the input shaft though. On the reassembly test according to the tech manual there was .170 clearance between 3rd gear and the outer syncro which calls for .040 and .100 tolerance. There were 3 shims at the rear of the main shaft. I bought 5 more shims to close the gap. This would take the slop out of the sycro assembly. My question is does this sould like I am rebuilding this right? Are there others receiving a main shaft pilot bearing with incorrect inner bore size?
Thank you
Bob McFail

Where did the shavings come from? You say everything looks good. You will need to check that out carefully; anything like that has a source and doesn't sound good.

The synchro has to have free travel in order to work correctly, follow the guide lines and don't take all of it out.

You need to get the correct needle roller bearing by part#. Many parts vendors have never been into a transmission, some don't have a clue what is right and what isn't. I have the correct # for obtaining a correct bearing from local sources at the shop. Let me know if you need that, will get it to you tomorrow.

[BobO]

Charles would that main shaft pilot bearing be 708267 Key BB? The bore of the worn one is almost 15/16. The one he sent me has a bore of 13/16. It sounds like whoever manufactured it got the length and the outer diameter right and did not consider that the mainshaft needs to go in there. Thank you once again for your advise.
Bob McFail

[Charles Talbert]

That is the military part#. No good for buying local; you need the number so you can go to a local bearing supplier and get it. I have local #'s for all bearings, you get much better quality parts that way too.

The bearing you need is a BCA brand, #J-301248.

You can source this at any local bearing supplier; just don't let them sell you some off brand Chinese knock off. Insist on a brand that is made in the USA or Japan, either will be a good product.

[BobO]

Super advise! I appreciate that Charles