t-20 popping out of forward gear

[RocketHurricane]

When I purchased my 400 Chief it had a worn shift lever on the left side, which I replaced with a new one. It worked fine at first, but within a few hours of use it started to pop out of forward gear on that side (left side). I pulled the shifter and the pin had worn already on the forward gear side. We just pulled the transmission and took that side apart. The teeth on the forward side of the shift collar are heavily worn, and the teeth on the carrier plate are also badly worn. You can easily see how it would the teeth would want to ride into neutral under load. I have a "new-ish" shift collar which I can put in, but given the wear on the carrier plate we suspect the issue could continue or at best quickly wear down the teeth my new shift collar. Since I don't have a replacement carrier plate, would it be possible to just flip it? The teeth on the other side of the carrier plate are not worn at all, but should they have a slight bevel on them to easy shifting? They are square edged. Other than that there seems to be no difference from one side of the plate to the other.

If it would be best to replace it, does anyone know the price? Can I get them from Recreative Industries, and will they work with an older transmission? Mine doesn't seem to have any thrust washers if that helps date it.

Thanks for any suggestions.

[jpswift1]

I'm pretty sure you are in need of a detent spring in the shift collar. It's a part that's only a couple bucks from Recreatives and it's easy to install once the transmission is apart. When you shift your transmission (by sticking a screwdriver where the diamond shifter goes) you should feel a nice firm shift and click into gear. If it is very easy to shift with the screwdriver and doesn't lock in/click into gear very noticeably, there's your issue.

[Bill Gerber]

I like the older carrier plates because they have those machined beveled edges. I think they shift better than the newer plates. The ones in the t-20's with the washers have stamped plates. So i use the older machined plates in the newer t-20's. I would say you could use the new ones on the old style, but never tried it. If you flip it to the square side i don't think it will go into gear because its spinning as its trying to drop in and once it stops it will never line up. Keep in mind when i say new i mean t-20's with the washers. The newest one i have had apart, was from the 70's. This might not solve your problem tho. On some of the old ones (without washers) that i have had apart. The planetary gears wear into the back side (drum side) allowing the plate to now ride a little closer to the drum. (It does run engaged in the plate in forward) Then the flat part of the teeth on the shift collar is not in the center of the flat part of the teeth on the plate surface, when in the detented position. A little wear on the edge of the partially engaged tooth and it becomes like a extended bevel, and pops it out of gear. This is what i found that made mine jump out of gear. The parts are not that expensive. I would call Recreatives and order a plate and try it and go from there. Tell them what you have going on and they will hook you up and tell you what to check. The guy they have in parts really knows that tranny well.
Wow, after re reading this i don't know if i even understand it. I hope it makes some sense. I think i had too many turkey sandwiches. And that triptafin is kicking in. I will edit this tomarrow and try to make it make better sense.

BG

[jpswift1]

You're good Mr. Gerber, haha. We can comprehend that loud and clear. I totally agree with you about the new T-20's. They're still great pieces of machinery, but I'd take an older one over a new unit any day. The supported main input shaft, the "popsicle stick" style levers, and the more precision machine work inside are just a few details that are now something of the past on them. I'd imagine the costs are what stopped these qualities from being continued on from the early 70's T-20's. My dad has a 2001 Max II with tracks and it can sometimes be a bear to shift unless everything is lined up just right, and trying to rock the machine back and forth to get it to line up with the tracks on it can be a challenge at times.

[RocketHurricane]

Here are some photos of my worn parts. The existing detent spring seems fine - it isn't broken and doesn't seem to be stretched out. My new but used shift collar came with a spring so we will install that one to see if it has an effect. I guess I should take the right side apart to compare the wear on the gears since that side does not have this issue.

Just to confirm, for forward gear the shift collar teeth engage with the carrier plate teeth, and the drum teeth for reverse. Do I have that right?




Below is the flip side of the carrier plate.

[JoeMeg]

Yes,you have that right,planet drum/carrier plate for fwd,ring drum for reverse.I'm far from an authority on the T-20 so anyone wishing to chime in,please do. The output shaft is retained by the snap ring against the inner race of the brg. What if the brg was not fully seated in the hsng? Would this allow the output shaft along with the detent groove for fwd to be "out" of the gearset enough that the pin is actually pushing the collar a bit too far (slightly beyond the groove) causing it to bear the load and wear so quickly? Just my thoughts,again,NOT a T-20 guru but your shift collar and carrier plate look ok to me.

Joe.

[MAX IV Mark]

Just a thought. It looks like those pins are sticking too far out to me(or the plate is too low). Look at George's assembly video, he has thrust washers added to the planetary gears, I dont think I see them on yours.

http://youtu.be/Vut0nOQgPHc?t=5m43s

[JoeMeg]

Mark,I think you just solved the mystery. I just looked at one of my disassembled T-20's and the planet gear pins are actually a fuzz below flush with the carrier plate. Also,on the one I'm looking at,the pins are pressed in until they are protruding out of the back side of the drum a bit,.020"/.030" maybe (didn't measure).

,,,

Joe.

[RocketHurricane]

I think Mark is on to the problem. When I compare the good side to the bad side the pins are nearly flush with the carrier plate on the good side and stick up above significantly on the bad side. When I put the carrier plate between the drums, there is no play on the good side but on the side that pops out of gear I can move the carrier plate up and down a significant amount. It looks like the difference is from the planet gears wearing into the hub. I will post pictures later.

[RocketHurricane]

Here is a link to a YouTube video showing the difference between the two side of my T-20. There is no play at the carrier plate on the one side and lots of play on the other. The planet gears on that side have worn into the drum a significant amount, resulting in movement at the carrier plate. I think this play resulted in the carrier plate not engaging the shift collar cleanly and under load forced the collar out of the forward detent, wearing the shift pin in the process.

We are going to look into machining the drum so we can add thrust washers or get a replacement drum. If anyone has a drum they are willing to part with let me know.

http://youtu.be/Ic8GpTB6RLo

[thebuggyman1]

You might try using just one fiber washer per planetary....that could be enough to take up the space you need without the expense of machining.

[Bill Gerber]

I think your hot on the trail
You need to space that plate out until flush with the end of the pins. It might be a good idea to switch the left plate with the right one, because of the worn side's of the tooth will be on the other side. Not the other side of the plate, but the other side of the tooth (The plate will be turning the other direction).
I have sanded down those washers before when needed. And it might be a good idea to even be slightly high on the pins to help account for the wear on the other side of the drum. this would push the center of the tooth on the shift collar, further into the plate. The washers really hold up well. I have purchased many rebuild kits only to tear down the tranny to find out the washers were only worn a couple of thousands and not necessary to replace. The bands are usaly not very worn either. But always be sure to put new o-ring's on the band plungers tho.
Make sure that one of the plugs is a vent plug (it has a hole thru the flats, then cross drilled down thru the center) and that it is on the top. I have always had a hard time keeping the oil in them. They came with dextron ATF in them. I have tried Fords ATF.
My Dad said that when at the factory he received feed back from the military at Fort Benning, GA. That the only thing they could get any life out of was 90W gear lube on the 8 wheel trainers in the southern heat. I am using it now in the race machine. and am using a Mobil one gear lube in Mike's trail machine. I can not notice any difference in handling, or oil loss for that matter. Still undecided on the oil thing. But haven't used dextron in years. I drilled out the vent plug and that helped on the race machine as it was getting real hot and the oil was getting pushed out due to case pressure. But the trail machines don't seam to get that hot. But they still leak. Someone told me that the new plungers have two o-rings on each plunger.
Good Luck and keep us informed.
BG
One more thing:
If you don't leave the rear chains a little bit loose it will get hard to shift into gear.

[RocketHurricane]

Thanks for he suggestion Bill. Where can I get the washers you mention? Are they in the rebuild kit you mentioned?

[Bill Gerber]

Yes
Its been awhile, but from what i remember the kit had, all washers, seals, gaskets (for where the half's bolt together), snap rings and o-rings for just under 50 bucks.
i asked them why not the output bearings. Recreatives said they almost never go bad. And know what?? I can't remember ever seeing one go bad. Except underwater salvage organ donors.

[Mike]

Yes
Its been awhile, but from what i remember the kit had, all washers, seals, gaskets (for where the half's bolt together), snap rings and o-rings for just under 50 bucks.
i asked them why not the output bearings. Recreatives said they almost never go bad. And know what?? I can't remember ever seeing one go bad. Except underwater salvage organ donors.

There is a photo of the seal kit in the T20 rebuild article in the how-to section of our site: How to rebuild a T20 Transmission

Also, Bill's comment regarding the output bearings is a good point. I'm sure they rarely fail. I take a very cautious approach to them though. If I get a new-to-me machine and have to rebuild the transmission for any reason, I typically replace the output bearings just because I already have it torn apart and they require you to completely tear the transmission back down to replace them. I would just rather do it all at once and not have to worry about it down the road if it were to happen. The downside is that those two bearings are very expensive and have to be sourced from RI since they are custom ground.