Transmission stucked in 3rd speed

miwi

miwi

Member
Hi,

I had rebuilt the transmission my own because the synchro blocker rings were heavily damaged. Since the rebuilding I drove around 1000 mi. I had sometimes the problem that I couldn't engage 1st or reverse gear when the car stands. I know it is unsynchronized and I double cllutching is the Thing shift unsyncho gears. My suggestion was that the clutch is the problem. But it was ok to drive it.

Yesterday I had the problem that my transmission was stucked in 3rd speed. I couldn't get the 3 speed out. I opened the box and the sleeve had over shifted. The pre synchro insert had tilt, so that the sleeve can't be moved back to neutral or 2nd Speed.
A closer look shows the following issues

  • rear oil baffle worn and loose
  • 0.05" -0.08" play of 2nd Speed and hub on mainshaft.
  • 2nd speed trusth washer (between 2nd Speed and 1st speed) worn.
So what is the root cause of the Problem? Does anybody of you has an idea?

Thanks for your help

Michael
 
Drain the oil and see if there are parts in the bottom of the case. When you re-assemble make sure the retaining snap rings for the bearings are the proper thickness. Is the 50 to 80 thousands a typo?? if not maybe you will find parts in the bottom of the oil that would allow end play to increase.
 
Mac VP supplies the correct thickness retainer rings but a lot of others dont. There are two types of synchro ring & hub. Some have the balls with springs and some have the steel plate detents with spring rings. The ones with the ball detents can sometimes get damaged. The 91A type shift fork should only let the synchro ring go so far either way. I wonder if it has the correct shift fork? The second gear wears on the main shaft and can get too much play at times. If you don't have Mac VanPelt's book, you might want to get one.
 
Used to happen to me when I attempted 'speed shifting'. Also took out some cluster teeth back in the day. Think you will be all right once you pry things apart. Make certain the shift is dead center when you put things back. Sometimes the rods change the bend slightly aggravating the problem.
 
I may be wrong but if the OP is standing still and can't get the trans in first or reverse...that says clutch to me. I spent years double-clutching in a Pete and Freightliner and never had a problem getting it into first and reverse from a stop.
 
Thanks guys for your advice. On saturday I'll get the transmission out of the truck. I hope that I 'll found not much damaged parts. I hope that I get all parts from Mac VanPelts.
 
I had this same issue with a 39 Box - with Lincoln Zephyr gears. It was a trans that I had built when I was about 16 years old, drag raced with it quite a bit and about a year ago threw it into my 32 Cabriolet (without doing anything). I could tell that it was a 'temporary trans' - it would not stay in 2nd, the synchros were worn, etc.. Finally, last summer it did exactly what you're talking about - locked up in third due to one of the synchron 'metal tabs' popping up and preventing the movement of the synchro slider back toward neutral.

The primary reason was due to a worn 2nd gear synchro - when the synchro slider was forward (in 3rd gear) the worn synchro gave the metal piece more ROOM to pop backwards toward the 2nd gear - and then pop-up.
 
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