mt_goat

Yes that's what the Marlin guys said, the coupler, but I'm having a hard time getting a picture in my mind of what it looks like. I would say call and call often, each time I call I get a different answer about the time estimate, but at least they know that there are people (with $$$$$) waiting on a solution.

sschaefer3

The coupler is a round tube with splines inside it. This connects two splined shafts with a seal around the coupler. The seal does not leak the ATF forces it's way through the splines in the coupler.

So now you ask yourself, so why doesn't the stock Toyota couple leak? and why does this Marlin one leak if it's the same except thicker?

That is the Million Dollar question no one has an answer to.

bamachem

sounds like the coupler needs to have a barrier plate in the center to seperate the two halves...

mt_goat

So is this round tube hollow all the way though on both designs?

Cebby

I called them - I talked to Dean at length.

The status of a revised coupler is "we have no idea".

But, being persistent like I am - and being between a rock and a hard place, I kept pushing. Apparently the "Epoxy Fix" is used in buggies and some daily drivers with success (they have some daily drivers running it for 6 months+ with no leaks).

They said they would make one up for me - ready in about a week. So I ordered up all the stuff I needed.

Steve - is the coupler the small cylinder with gears on the outside in front of the gaskets behind the bolts?


Does it leak around the outside of it, or through the center?

Cebby

I was thinking the same thing. I might need to try to waterjet cut something out of aluminum that is a press fit. When the ATF heats up and thins out, the aluminum would expand and make a nice tight seal (in theory).

bamachem

yeah, that's the coupler, and yeah, that's what i was thinking too...

cut something on a cnc laser machine that will be a tight press-in fit and will expand w/ the coupling upon heating.

sschaefer3

It leaks through the center.

Here is a pic of my coupler. It goes from 26 spline to 23 spline.



That is the coupler right dead center, if you look down the middle of it you can see the end of the 26 spline shaft from the tranny.

The spines you can see are 23. Than that geared thing goes in the old gear case and it goes back to 26 spline, for me that is. Yours will stay all 23.

sschaefer3

They made 2 of them like this and actually cut slivers of the tranny output shaft to press in there and seal.

I think this is the epoxy/jb weld solution, form what cheese told me, they are having a hard time machineing the slugs so they are snug but don't leak.

Cebby

BTW - they said they'd swap out mine to the revised version when it becomes available.

Steve - any idea how much room is between the two shafts inside the coupler? Does your coupler go 23 spline directly to 26 spline? Or is there a flat area with no splines between the two splined areas?

sschaefer3

There must be some space in mine, but honesty I never really studied it that hard and I have only actually seen in a few times.

When we pulled the crawler the first time Vernon was amazed at how thick the thing was, he had only seen stock stuff up until that point, that's really all I can add, since mine is a bit different.

Also the 4.7 gears did make a bit of noise when first installed like a gurgeling sound when in 1 to 1 and you took off hard, but now they are broke in and perfectly quitet.

Praufet

If the sleeve is hollow all the way through why can't they just put the barrier plate in it like leave a 1/4" of material between the two shafts.
So instead of ======
its ====|====

sschaefer3

I think that is exactly what they are trying to do but no one can make it.

mt_goat

So what do the Toyota factory couplers look like?

Cebby

I'll tell you when I pull the tcase off of the A340F trans tonight.

sschaefer3

I don't remember and mine was left at Marlin Crawler. So Mike will have to show us.

I think they had to use a puller to get it off, but the 26 to 23 one you don't. I know that for sure.

bamachem

well, that tells me that the tolerance on the 26/23 isn't as tight as the tolerance on the OEM one.

sschaefer3

Yes, but that 26/23 is fine, the problem adapter is the 23/23.

I don't think a single 2.7 Auto has ever had a crawler installed.

Cebby

Got the case off tonight. Piece of cake. It seemed like the bolts holding the TC to the tailhousing weren't torqued much more than 30 lbs. (Just a guess).

Now, the coupler is another matter. That thing is ON there. I didn't want to run the risk of messing it up, so I didn't try too hard.

I think in discussing this we've found the answer. If these couplers have a consistent inside diameter, then the problem isn't with the coupler being too large, but the tcase input being a thou too small. If the OEM one is SO tight that it can't be pulled off by hand, that means the trans output and the tcase input are two diffferent sizes. My .02 anyway.

There is nothing between the shafts in the OEM couplers) I'll try to figure out how to measure to see if there is any space between the shafts. Might be tough without pulling the coupler.

Here's a few pics of the coupler:

Cebby

Here's some pics comparing the a341 and the a340f.

A341 bellhousing:







A340F bellhousing: