Borg Warner Super T-10 problems

[jdincau]

H all,
     Sunday morning at El Mirage we warmed up the engine and drive line in the pits on jack stands and set the timing. All went same as usual so we were set to run. Waited our turn and three cars back from the line we start it up to get it up to 180. Shut it down tighten the belts and go to push it forward. No go, trans is locked up and won't shift. Tony held the clutch in and we towed back to our pit. We took the linkage off to get that out of the equation but the 3 - 4 lever won't move. Today I pulled the trans and put it on the bench. Shifter forks look fine no blue no gouges. 1-2 slider will move, 3-4 won’t. No swarf in the case light synchro dust in the oil. Main shaft will not turn freely turns about 60 degrees and binds, turn it back, same thing. Front bearing retainer off, snap ring off, pull front bearing. Bearing is fine. Tail shaft off, mid plate unbolted, both sliders forward and snake the main shaft assembly out the back. Removed the front input shaft from the assembly, needle bearing race and needle bearings pristine. Remove snap ring to get 3rd gear and 3-4 slider off and the synchro assembly comes out the front as I am sliding it off the rear shaft. I honestly don’t know if it was still together correctly when I started or not. The slider synchro mechanism involves two springs three dogs and two synchro rings. It is very fiddley to get together right and seems to want to disassemble itself at the slightest touch. I checked the rest of the bearings and all roll smoothly with no snags. I re assembled the 3-4 slider and synchros and put the main shaft back together. It turns freely and both sliders work smoothly. I can only think that somehow one of the synchro dogs got free inside the slider and was jamming the mechanism but I can’t tell for sure.  I am no transmission expert can anyone out there shed some light on this?

[kiwi belly tank]

Not knowing the history here, I'll take a stab at it.
I would say one of the synchro dogs dropped out & loaded one of the cones. One end of each spring has a hook on it & should be in one of the dogs to prevent the spring turning, if it wasn't in or is broken off, it will allow it to turn & leave one dog not loaded allowing it to drop out.
Make sure the 3-4 fork is going full depth in the shift ring, I've had to space them before.
  Sid.

[jdincau]

Thanks Sid,
In light of your response I am going to take a closer look at all the synchro parts. The three synchro dogs are retained by spring wires front and back of the slider with a hook at each end. When installed inside the dogs forcing them out, the hook is against the side of one dog, the wire spans the next and the hook on the other end is just past the third dog.  Is it important that the installation be symmetrical as far as front and back on the slider?
Jim

[mike f]

Hi, Mike from MF performance.  What year is this trans?  BW made different dogs for different years and different synro rings also.  Some new rings have the wrong angle on the cone and will not work on US made gears.  Also the hubs from early T10 and later T10 are also different. Was this trans. just rebuilt?  Matching correct parts is the biggest problem with both BW T10 and Munice.  Last but not least is any gear froze on the shaft?  First gear on all T10 and Munice trans. should be rollerized.  Hope this helps.  Mike

[fwillyj]

-back in about 2003 at Bonneville we had installed a super T-10 into Zupan's #1727 roadster and had the same exact problem.

-first run down the track was fine until trying to make the shift from 3rd to 4th----seems like it was locked up in 3rd.

-come to find out the 3 synchro dogs had tipped up on an angle when it went into 3rd and that locked the hub from moving into 4th.
-----------------------------
-apparently there are two types of synchro dogs----one type is like a piece of stamped steel and the other type is more of a solid forged looking piece.
------------------------------
--I have a note attached to one of the forged looking pieces stating that "these break".

-apparently the overall height of the forged piece is .225" which includes the small short detent bump on the top.
-----------------------------
-I don't remember which type we had---pretty sure they were forged looking type---but there was a roadster guy near us when went looking for parts---who knew all about the problem---but didn't have any parts.

--but he did have a piece of 1/4" square steel key stock that he said would work fine to fabricate the 3 dogs----but to make the small short center bump .280" overall length instead of the about .090" stock length.

-we spent a ton of time getting the trans apart without the right pullers and pushers to get the front bearing off and back on---but we found some files to file the square stock into 3 synchro dogs with the longer top bumps.

-spent at least the rest of that day and part of the next day to get it all back together.
--------------------------------------
-these hand fabricated dogs worked excellent and got us thru the event and several more with no more problems.
--------------------------------------
-after the event I built a special puller to pull the front bearing off the input shaft while it was still in the trans case---and then I also built a "pusher" that clamped onto the input shaft with 9 set screws that are what I consider to "Bonneville essentials".

-my notes also state that we made another set that is .280" overall height with the .280 hump length.
---------------------------------------
-That trans belonged to another Bonneville friend and it was returned after the 2004 season so I don't know any more about it----other than I had "slickshifted" 2nd---3rd and 4th gears just before when we first installed it and had this problem.

[jdincau]

Thanks guys,
The trans is a late model super T-10 (1974 case) and was rebuilt in 2012 to change the third gear ratio. It has been working fine since then. All the bearings and shafts seem fine. It is behind a 180 cubic inch, 14/1,  4 cylinder motor and running the drive train at idle has some big vibration modes. I am thinking the shaking somehow dislodged one of the synchro dogs. I am going to inspect them carefully and compare them to the used parts from the rebuild to see if something has broken.
Jim

[Ron Gibson]

Back in 68 when I was doing repairs (they couldn't afford rebuilds) for the local young hot rodders, those syncro lugs were a problem then. The block ones are made out of powdered metal. That's why they break. Powdered metal technology has greatly improved since then, BUT. The stamped ones are better if available, or make your own as mentioned. 

Ron

[jdincau]

    Synchro dogs and keeper springs all look good. The dogs are the long lump type. One synchro ring has the slots for the dogs rounded over. The 3-4 fork is worn. Strangely the 3-4 slider looks fine. I am ordering a new fork and synchro ring. As Russ suggested I will assemble it and try the shifter, if all seems OK we will put it in and try running it on the stands. Thanks for the help to all.

[mike f]

Hi, For all you that are having brass syrno problems try using steel banned ones. They cost a bit more but will NOT stretch.  Remember the brass ring does not lock the gear only slows the gear to allow shifting.   Remember to look at the slider, there are many different types, if the points get damaged the slider will lock and not allow a shift.  Hope this helps.  Mike