What EXACTLY does a blown 1st gear synchro feel like?

[amaurer]

I have an H41 with a first-gear-popping out problem. I know the H41 is known for losing the first gear synchro, so thats my suspicion, but I want to check...

My shifting is still fine, no problems going into #1. However, when barely moving, usually when pulling out of a parking spot, the transmission will slip out of gear. The shifter only moves maybe 1/2" and appears to be still in gear, but its not. I have to pull the shifter back to neutral before I can put it back in gear. Its not violent, by any means, its sorta like :: not in gear anymore.

Its worse when the rear of the truck is low, as though the weight of the shifter itself is enough to tug it out.

So, classic synchro symptoms?

 

[Pin_Head]

Yes.

There are two different aspects to a synchronizer assembly: The brake ring (usually bronze) and the clutch hub/slider ring and the dog teeth on the driven gear that couple the input shaft to the output shaft. Popping out of gear is due to wear on the clutch hub/slider ring, the dog teeth on the driven gear or the bearing that the driven gear rides on the output shaft. Wear on the brake ring produces grinding on shifting when the truck is moving.

 

[Tankota]

Doesn't sound like a syncho. Sounds like what pinhead said. The spring with usually three little extra teeth that sorta float and hold it in gear (at least thats how it is in most of the trannys I've had apart).

ps must be nice to have 1st gear synchros I've had sm465s in my cruiser since 1996!...no 1st gear synchros there!

 

[grant5127]

check the dentent ball and spring......

 

[amaurer]

check the dentent ball and spring......

Bingo.

Turns out one of the springs had broken but I didn't notice that the "short" one was only a fragment when I reinstalled it long ago.

Works great now with a new spring.

 

[rockcrawler]

Bingo.

Turns out one of the springs had broken but I didn't notice that the "short" one was only a fragment when I reinstalled it long ago.

Works great now with a new spring.

Yeah had the same problem on a 4 speed years ago, kept popping out of first, same fix. I'll always remember it as I dropped the box flange on my right hand on pulling it out and ended up getting five stitches for my stupidity from an apprentice doctor On top of it I had to disassemble/re-assemble it and fit it back on the next day with mostly my left hand (am right handed) as I had heaps of work on and no other mode of transport.