Need serious techincal advice on my M50D transmission.

[gw33gp]

On my way to Kansas from CA my M50D transmission began popping out of 5th gear so much, I had the drive most of the way in 4th. My brother is a professional mechanic and has his own shop in Kansas. We dropped the transmission and opened it up to have a look. We can find nothing wrong but have just looked at it with the top and back end off. We did find a lot of very small pieces of what appears to be hard plastic that is black and kind of greenish that was trapped behind the beige plastic cap that is over the nut at the back end of the countershaft. We have no idea of what it could be.

There was also a fair amount of very fine metal on the drain plug magnet. The transmission was gone though about a year ago by a recommended transmission shop. They replaced the 5th/reverse cluster as well as all the bearings and seals. It was working fine until now.

My brother is not a specialist on the M50D but knows transmissions fairly well. He is baffled at what it could be. We could take it further apart but not sure what to look for.

We found detents on the shift rods for 1st, 2nd, 3rd and 4th, but no detents on the 5th/reverse shift rod. The lever for the 5th/reverse cluster snap into 5th and reverse and seem to be held there firmly. What is odd is when the transmission was in the vehicle the shift lever seem to have a lot of play back and forth when in 5th. Gears 1 though 4 did not display this looseness. What is the mechanism that holds 5th in gear? What would cause it to pop out of gear?

I plan to be in Kansas for a little over a week, but need to get this resolve soon. Please help if you have any ideas what to look for.

Information on my truck is in my signature.

 

[rusty ol ranger]

Usually when they pop out of gear its a syncro

 

[gw33gp]

The syncro looks good when looking at it from on top. When the 5th/reverse cluster was replaced a year ago they said the sycros where is very good condition. Is there something that can't be seen from looking at them from on top that we should be looking into? We can tear it down further, if we know what to look for.

I am still concerned about all that gritty hard plastic we found and what the source of that it.

 

[Uncle Gump]

@Transman304 you have anything you can offer to help a fellow ranger person out?

 

[Shran]

Any wear on the 5th/reverse shift fork itself? That would be my first guess...also likely based on the shifter slop you're talking about.

Greenish plastic IMO can only come from one place: the shifter bushing.

 

[Transman304]

Check the mainshaft lock nut. Sounds like it came loose and is letting 5th speed gear move .
Brad

 

[gw33gp]

All the shift forks including 5th/reverse are in excellent condition. That is why it is baffling me about the slop. Maybe the shift bushing is worn and that is where the plastic debris came from and is contributing to the slop, but I think it would show up as slop in the other gears also.

My brother has asked around and it has been suggested the 5th/reverse cluster needs to be replaced again. He is going to take it further apart for closer inspection.

Thanks for the info on the on the possible source of the green particles.

We will check the mainshaft locknut. Thanks for the tip.

 

[rusty ol ranger]

Might be further ahead just to go get a good used trans

 

[gw33gp]

The mainshaft locknut looks good. The stake is still in place and the locknut is tight.

What we did find is the lower shift bushing is totally gone. The top one is intact and looks good. I have been getting some light rattling in mostly 1st and 2nd recently. That must have been the shifter ball vibrating on the aluminum. It could also explain all the green particles.

Do you think the missing lower shift bushing could cause it to pop out of 5th? Maybe it was not getting all the way into gear far enough to hold it in gear. If so, how far do you think we need to break it down to get all of that plastic debris out?

 

[Shran]

I feel like a missing bushing could certainly cause that issue.

The only place I'd really worry about the chunks being is in the oil trough that feeds the input bearing. If they're small enough or several larger ones, they could clog the oil passage there. Maybe you can snake a bore scope through the shifter hole and see if there's anything in there.

Everything kinda drains towards the back of the trans and debris seems to end up down by the drain plug area. I found a nice shiny shift fork roll pin down there one time. If you can find most of the bushing and get it out through the back of the trans with the tailhousing off, you're maybe OK... there are probably a million of these transmissions running around with bushing chunks in them... on the other hand, every single one I've torn down has a lot of crap in the oil trough. You're this far, might not hurt to pull the top cover off and clean everything out. Complete disassembly is not necessary IMO.

 

[racsan]

if its just 5th, you can drive it like a 4-speed and not worry about it, you dont really lose much mpg that way. Now if you lose 2nd, its a pain to drive, I wish Id been that lucky several years ago.

 

[gw33gp]

Thanks for helping to confirm the missing bushing could cause the 5th popping out of gear. We have gone with that and have ordered parts to resolve the missing bushing issue. Pulling the top plate was the first thing we did, so should be able to get most of the crap out. I was just concerned there could be more pockets that stuff could get caught in.

 

[gw33gp]

This is a follow up on the issue with my transmission. After installing new shifter bushings the transmission shifting felt firm and snapped into the detents very well without any slop. We felt confident that would eliminate the popping out of 5th gear. The test drive showed it was better but acceleration in 5th resulted in popping out of gear again. I drove it to CA again in 4th.

Once I got home, I called the shop that did the rebuild last year. They told me to bring it in and they would look at it. The day after I dropped it off they called and said it was ready to pick up. They found the 5th gear and slider were worn and replaced them. They felt the missing shifter bushings kept it from going all the way into gear resulting in excessive wear on 5th gear. Even though it was just past the warrantee period, they did the work at no charge. I also asked them to replace the rear output seal on the transfer case because it was leaking a little. They didn't do any work on the transfer case during the transmission rebuild but did not charge me for the seal replacement this time.

I was wondering if they would stand behind their work and was prepared to present an argument. They proved to be the professional shop I originally thought they were. I think the only mistake they made was not replacing the shifter bushings during the rebuild.

 

[Transman304]

Thanks for the update! Always nice to find solution and an honest shop.
Good luck
Brad

 

[NakedDucks]

Are the “dots” on the syncro collars lined up the proper way?

I bet they reversed it....especially with you saying it had play in 5th.

Let me guess..... all gears shift fine. Go to 5th and it pops out under load or acceleration? But will stay in reverse with no problem (reverse it the other gear handled by the 5th gear syncro collar)

If you need a pic of the collar dot I’m talking about, let me know.