got my transmission all apart and now I'm putting it back together, its a turbo s4 transmission. I have the lunchbox put back together (all the gears inside the central casing) but for some reason something is binding the input shaft to the output shaft and it isn't the shifter sleeve. when I put the sleeve in 4th everything spins but if I take it out of gear and then slide it into another gear it acts like its in 2 gears at once but its not, and I cant move the input shaft independently from the output shaft even when all the shifter sleeve are in the neutral position.
so what could it be? I know i probably didn't put something back together right but I want to know what it is before I start pulling those bearings back out.

 

on the M box when you put the input shaft bearing on it can jam the 4th gear synchro, not bad to pop it apart, maybe this is you?

 

you mean the big bearing holding it to the housing or the little one thats inside the input shaft

 

4th is direct drive, so you should have the input shaft locked to the output shaft, and the countershaft rotating according to the input shaft. If everything is spinning ok in 4th, that means 1st and 2nd aren't binding or engaged. It also means that your front bearings should still be at an ok depth (input shaft and countershaft teeth would start eating each other if not). I agree with j9fd3s that you likely have a problem with the bearing that goes inside the back of the input shaft. If that is bound, you will only have a direct drive scenario because the input and output shafts can't move independently. Load that sucker with grease prior to assembly.

 

ok,, got it. i greased it up prior to assembling, maybe i just put it in at a wierd angle, that box doesn't leave much wiggle room. do you think I may have busted it?

 

There is another point to consider as well. Can you spin the 4th gear synchro freely when the 4th gear forks aren't engaged? If it does not spin, it could be that the input and output shafts are too close to each other and may need shimmed to space them apart correctly. If the 4th gear synchro can spin freely, then the problem is with alignment, or that intermediate bearing.

 

I dont think the Syncros are supposed to spin 100% freely because they have little notches in them that make room for the shifter sleeve assembly.

 

Yeah, I worded that wrong, had to work late last night and I need more coffee. What I meant was can you wiggle the synchro or is stuck with the input shaft?

 

ok, then yea I can wiggle it. what's odd is i can spin the shaft a degree or two and then it will catch on the output shaft as if its catching on the synchro. I double checked to see if it was a clearance issue today and backed the input shaft out a bit and all that did was make the counter shaft not mesh properly and the output shaft was still linked with the input.

Edit: lubed up the synchro and pulled the input shaft away from the output shaft a bit and it finally budged. the counter shaft gear that meshes with the one on the input shaft isn't meshing right but I think that's because I don't have that bearing installed yet because if I hold it in place with my finger on that end it cooperates. thanks for the help

 

Fantastic! Sounds like you'll need to spend some extra care on shimming. Its not a fun crunchy noise when the input and countershaft aren't depthed correctly and it was your first transmission rebuild and you were so proud of it and you just showed your wife...
Let us know if you need anything.

 

ok so I'm at a loss. I can pull apart the input and output shaft and the input wont bind but doing that pushes the bearing out of the case a little so if I put the bell housing back on it pushes on the bearing which pushes the whole input shaft and im back to square one with the shafts squeezed together. I put that bearing as far down into that shaft as possible so theres no more room for adjusting. so, what now? should I put it all back together and hope the lube free's it up?

 

Couple things here.
1. Did you keep the C-washers near the rear mainshaft bearing separated into front and rear sets when you disassembled? The manual says they can be different thicknesses.
2. Are you re-using your mainshaft and countershaft bearings? If not, you will need to tolerance and shim the transmission to within that tolerance or the sucker will be either too sloppy and break, or be locked up. There are shims that go either above or below the great big snap ring (that you used the puller on), for the input shaft and counter shaft front bearings. For the output shaft, make sure the C washers are correct (or if they're the same size, don't worry about them) and there is a thrust washer that goes in between the output shaft bearing and the 1-2 gear pack. This sets the correct tolerance for the output shaft. There is also another thrust washer on the other side of the bearing and the whole shaft is squeezed down by the nut on the end.

How far did you take this thing apart? What parts are different? Let's start with that and we can get you going. Nothings broke yet!!!!!

 

replacing bearings and synchro's, not replacing the needle bearings in the gears. Do I get new shims from mazda? also it looks like there issnt a lot of room to adjust for shims because the bearing on the output shaft has a plate that goes over it and its a pretty snug fit.

 

You need to measure first. This is one of those measure ten times, cut once type things. You can see if you can get new shims from Mazda. They might carry them. If not, you can buy shim stock and make shims. The thrust washer that goes in between the 1-2 gear pack and the output shaft bearing is also clearanced, so you'd need to check that it is in spec. The output shaft doesn't use shims. It uses different thicknesses of thrust washer instead to take up its position. Is it possible that you have that washer installed incorrectly?

Before you start ordering stuff, you need to go through and re-inspect your work. Did you get the gear packs pushed back on the shaft in their correct position? Is there a washer or spacer in the wrong position? Print out the manual and cross off that each piece is where it needs to be and is moving or not moving correctly. Start from square one.

 

I popped out the bearing holding the output shaft in place and pulled the washer in between that and 1st gear (I think that is what it is). I put the bearing back in without the washer and everything seems to play nice, only thing is there is a fair bit of play in the output shaft. do you think I should grind down that washer? or is that something I should be doing?
also what end play should I be looking for on all shafts? I cant seem to find any specs on the online FSM or my book

 

FOUND THE ISSUE! the input shaft bearing wassnt on all the way so the input shaft was deeper than it should have been, everything is working now

 

Good to hear!