My transmission is slipping/popping out of gear!

[66ChevyTailgater]

Here is my predicament:
When traveling down the highway, my bus is starting to pop out of 5th gear. It happened 5 times in a 2 hour period yesterday and while not anything more than inconvienent, it makes me think it is a symptom of a bigger problem.

We have a 5 speed manual mated to a 350. It is a 66 Chevy with a Wayne body.

Thanks!

[Eric von Kleist]

I'll through out a couple of maybes...

bent shifter fork

bad detente

missing tooth(s) on gear(s)

Is it doing it while under torque/acceleration, or when you decelerate? My son's Cherokee does this occasionally when you lift your foot off the gas pedal while driving in 5th gear or decelerate hard, but it will not do it if the engine is actively transmitting a load to the transmission.

It hasn't gotten any worse in several years, so we just kind of got used to putting a hand on the shifter when decelerating in that gear. That's all the pressure it takes to keep it in place.

YMMV

[66ChevyTailgater]

Originally Posted by Eric von Kleist

I'll through out a couple of maybes...

bent shifter fork

bad detente

missing tooth(s) on gear(s)

Is it doing it while under torque/acceleration, or when you decelerate? My son's Cherokee does this occasionally when you lift your foot off the gas pedal while driving in 5th gear or decelerate hard, but it will not do it if the engine is actively transmitting a load to the transmission.

It hasn't gotten any worse in several years, so we just kind of got used to putting a hand on the shifter when decelerating in that gear. That's all the pressure it takes to keep it in place.

YMMV

It generally happens when there is some type of load on the engine, either from acceleration or just holding speed. How would one go about diagnosising this?

[Wolfman]

You probably aren't going to like this, but pretty much any of the problems that are symptomatic of popping out of gear are going to require cracking open the case. Since you're apparently only symptomatic in one gear, I would want to put bent forks or linkage at the bottom of the list. Due to the age of your bus, I'm not sure if you have a synchromesh transmission or not. The dog gears that engage the power gears, or the powr gears themselves are quite likely worn.

[66ChevyTailgater]

Originally Posted by Wolfman

You probably aren't going to like this, but pretty much any of the problems that are symptomatic of popping out of gear are going to require cracking open the case. Since you're apparently only symptomatic in one gear, I would want to put bent forks or linkage at the bottom of the list. Due to the age of your bus, I'm not sure if you have a synchromesh transmission or not. The dog gears that engage the power gears, or the powr gears themselves are quite likely worn.

I forgot to say that we've popped out of second gear a few times also. This is really our first gear because first gear is such a granny gear.

Does that change anything?

[Wolfman]

Since 2nd gear isn't likely on the same shift fork, no. It just sounds like your tranny is in need of a rebuild.