Won't go into 2nd gear.

[Deno]

Hey all, just picked up a bobbed 1979 M35A2 from a local guy who did the conversion, used it a few times, his wife hated it so it sat for about a year in a field. Got it cheap.

After rebuilding the Airpack, Bleeding the brakes and tagging/insuring her, it was time to bring her home.

A test drive around his neighborhood revealed no bad habits, she went through all gears no problem, had no blow by on start up and no air leaks on shut down.

A few things he said didn't sit right compared to my pre buy research, "The lever (hi/low, it is not an air shift, its a sprag model) engages the 4x4", "Don't bother starting in 1st, its too low a gear", stuff like that. He did strike me as honest and genuine and helped me fix the airpack, wife fed us dinner, etc...

When we set out for home it ran fine and held a steady 54 mph with no issues. About 10 minutes into the drive, I decided to pull into a gas station to top her off, I downshifted carefully from 5th to 3rd in low range, and as I pulled in I attempted to put it in second. It would not go, it was as though a wall was up. I then drove it to a small airport I work at that was near by and began trouble shooting, here was what I found:

1. It would not enter Second gear, the shifter would not enter that position.
2. It had been working fine previously, I had no issues getting into second gear the 5-6 times I had test drove it/shook it down prior to this.
3.It gave no warning, made no noises and had been running fine.
4. I tried double clutching, slipping the clutch, downshifting into it from 3rd while moving, forcing it, yelling at it and voodoo and it simply would not go into 2nd.
5. Upon removal of the top cover the gearbox looked clean, and no ground gears were evident, the carrier between 2nd and 3rd looked ok, and moved about an 1/8th of an inch forward and backwards, also, Continuity in the shift box was checked and it seemed to go into 2nd no issues, it did move the middle fork rearward and the fork appeared to be in good condition.
6. The fluid was old, smelly and slightly low, The transmission does seem to have a howl, and I am sure it could used flushed.

I am a bit confused, and I cannot find any other threads that explain this SPECIFIC issue.

What did I break? Synchro? Bearing? Bushing?
Could the shift box be out of adjustment?
How would you recommend flushing the trans, and what fluid to use for the flush and the refill?
Are parts readily available and where if I have to rebuild? (have access to a full machine shop, can use a hammer)

Any other ideas? Questions?

Im sorry to be so long winded, I just wanted to cover everything instead of making 30 follow up posts.

Thank you in advance

-Deno

 

[tommys2patrick]

does the shift issue stay the same whether the Transfer case is in high or low range? I assume the test you did with tranny cover off, when you saw 2nd engaging, was with engine off? Can you up-shift from 1st to 2nd in high range transfer and then into 3rd with engine on and moving forward?

 

[tommys2patrick]

also, can you take a magnet past the gear cluster into the bottom of the tranny case and check for foreign material. something may be laying down there you can't see from above. Tranny fluid is not so expensive that you can't just change it out. drain it into something that lets you look at the fluid.

 

[cattlerepairman]

Maybe as simple as a bent shift fork from previous attempts to get it into second? Ideally, you could swap tranny tops with a known ok shifting transmission and see if yours performs better with a new top.

 

[rustystud]

I would also look closely at the synchro. Are there any burrs on the "dog clutch " teeth ? Is the bronze on the synchro still smooth and round ? The bronze rings are held in place by rivets that can come loose. They must operate smoothly in the gear. The purpose of the bronze rings is to "speed up or slow down" the gear to the mainshaft speed.
Another thing it could be is the ball and springs in the synchro. It would be extremely difficult to diagnose this as the springs and balls are in those holes on the slot where the shifter fork rides and you really cannot see them. They control the detent you feel when shifting. If as you said this truck set for a year it could have some rust on these balls and when you started shifting it caused this rust to come loose and "jam" the movement. I would get two pry bars and push the synchro into 3rd gear then force the synchro into 2nd gear. If it will not go then you will have to remove the synchro and either clean it in some anti-rust solution and hope it works or just get a new synchro.

 

[Deno]

We isolated the issue to the Synchro, we drained all the fluid and it was disgusting, and had a putrid odor, however it had no metal in it. We put in 30 weight non detergent and immediately the transmission sounded better and shifted better into 134 + 5, but still no 2nd gear, we have a new 2/3 Syncro on the way, does anybody have a link to a video on how to install a synchromesh? We have a full Machine Shop with a press to our disposal, we just need to know how to do it, I've been reviewing the TM but it would be nice to see a video or some photos, thanks in advance guys!

-Deno

 

[rustystud]

We isolated the issue to the Synchro, we drained all the fluid and it was disgusting, and had a putrid odor, however it had no metal in it. We put in 30 weight non detergent and immediately the transmission sounded better and shifted better into 134 + 5, but still no 2nd gear, we have a new 2/3 Syncro on the way, does anybody have a link to a video on how to install a synchromesh? We have a full Machine Shop with a press to our disposal, we just need to know how to do it, I've been reviewing the TM but it would be nice to see a video or some photos, thanks in advance guys!

-Deno

You can remove the mainshaft from the transmission with the transmission still in the truck. You will have to remove the transmission to transfer-case "jack-shaft" driveline. Then remove the output flange. After that you remove the seal housing. After you remove the top cover (which it looks like you already did) you can use a "drift punch" to slowly drive out the rear bearing about a 1/4" to 1/2". When you can safely get a puller on the bearing, remove it. Then you can lift up the mainshaft and moving it backwards until it clears the input gear you can then lift it up and out of the case. Then it's just a matter of disassembling the mainshaft gears until you get to the 2-3 synchro. I would drain the transmission first since you will be dropping the input gear mainshaft bearings into the case.

 

[gringeltaube]

.................................................
Any other ideas? Questions?
........................................

That dark area between second and first looks suspicious to me... Over-heated?

We have learned already that 2nd has a tendency to seize to the mainshaft. ... Which may affect the 2[SUP]nd[/SUP]-3[SUP]rd[/SUP]
sleeve as well - causing the keys to shear and the sleeve to expand or even split open.
All that could explain that the synchro-hub would not move far enough back to engage 2[SUP]nd.

[/SUP]You did not mention if you could "manually" put it in 2[SUP]nd [/SUP]gear, with the top cover removed...?



G.

 

[Deno]

We could not manually get it into 2nd with the top case off, if it is seized, what parts would need to be replaced? What causes this?

 

[dmetalmiki]

As you pointed out already, poor lubrication, and or very dirty inadequate transmission oil. Keep us posted with the usual pictures, you sound to have a grip on the situation.

 

[Deno]

Progress

So after ordering a new Synchromesh and gasket set, carefully reviewing the TM's and getting some advice from a some helpful folks(Big mike, guys at the FB M35A2 page) we pulled the gearset tonight through the top of the case. Went relatively smoothly and being prepared with lots of good tools helped tremendously. Here is what we found...

-The Shaft did show signs of high heat, but nothing was seized, thank goodness.
-We have not pressed the 2nd gear off yet, We ran out of time. We do have a press and fabricated a "die" to hold 2nd in place while its being pressed as per the TMs.
-The synchromesh would NOT engage into second gear, even with a breaker bar, but would into 3rd.
-As already mentioned the previous gear oil was terrible looking/worse smelling and was likely decades old.

We will be finishing disassembly/beginning reassembly tomarrow, any further tips to help with reassmbly would be greatly appreciated!

Thanks again SS crew!

-Deno

 

[Wildchild467]

Side note: I put Mobil 1 SAE 50 Transmission Gear oil in my truck and the transmission loved it. Its expensive at $100 for 2 gallons (only needs 5 for a PTO transmission), but I think its worth it. None of the other gear oils seemed to work as good as this stuff. I also installed a magnetic transmission drain plug.

 

[yolner]

Side note: I put Mobil 1 SAE 50 Transmission Gear oil in my truck and the transmission loved it. Its expensive at $100 for 2 gallons (only needs 5 for a PTO transmission), but I think its worth it. None of the other gear oils seemed to work as good as this stuff. I also installed a magnetic transmission drain plug.

Wonder if you could put the same stuff in the transfer case too. Seems like it's GL1/GL4 and yellow metal safe so on paper should work.

 

[Deno]

Wonder if you could put the same stuff in the transfer case too. Seems like it's GL1/GL4 and yellow metal safe so on paper should work.

where in rockville? I grew up in hungerford, went to richard montgomery HS, I used to own "Stiles towing"...been in Florida for a 6-7 years now.

 

[theeDIZ]

Rm what year?

 

[Deno]

Rm what year?

Left and got my ged in spring 03 when I was 17, mom died so it was a tough year, started college at mc that fall

 

[theeDIZ]

I was class96 lived off crabsbranch

 

[rustystud]

Side note: I put Mobil 1 SAE 50 Transmission Gear oil in my truck and the transmission loved it. Its expensive at $100 for 2 gallons (only needs 5 for a PTO transmission), but I think its worth it. None of the other gear oils seemed to work as good as this stuff. I also installed a magnetic transmission drain plug.

That's a great gear oil to use. I also like Shell Spirex 50W.

 

[yolner]

where in rockville? I grew up in hungerford, went to richard montgomery HS, I used to own "Stiles towing"...been in Florida for a 6-7 years now.

I actually just work in Rockville. Live in Damascus, but nobody seems to know where Damascus is. Wish I was in Florida too!

 

[Deno]

Well when we break something, we "pro grade" break it....

We pressed off 2nd and this what we found....it now makes sense that it would not slide into second no matter what I did.
As you can see, she is "gudenbroke"...

To recap, This occurred on the drive home, after attempting to shift into 2nd from 3rd at about 15 mph after running for 10 minutes in 5th, second had previously engaged no issue the four or five times we had driven it, and had given no warning signs of failure. It should be noted the previous owner indicated he had "Always" started off in second gear, and seldom used 1st....I know this is an old debate but it's worth noting. We drained decades old trans fluid from it after getting it to the shop that would be best desribed as "Putrid". We found no metal, but there was obvious evidence of overheating on the components.

A few questions,
-What caused this? Poor lubrication? A failed synchro? Operator error?
-What can be done to prevent this in the future?
-We intend on using 40 weight non detergent oil, as we already have purchased some, is this sufficient?
-What TM would have these part numbers/what is the smaller geared piece called?
-Best place to source these parts?

Thanks again for all the support from the SS crew!

-Deno