The Stovebolt Site Forums The Shop Area Engine Shop Popping out of third gear

Good Morning All...I have a 52 3100 with a three on the tree. When I go down the road it will pop out of third gear. If I hold my hand on the shifter, and maintain pressure it will usually stay in gear. If I just put light pressure on the shifter, I can feel when it is going to pop out, and if I let up on the gas, and then resume speed, it will stay in gear. Anyone experience this problem, or have a solution. Thanks. I have checked linkage adjustment, and it seems fine.

welcome to the garage snook, the best place to find out that you've got a problem most stovebolters encounter eventually - old age does creep up on ya

worn syncros are the cause, rebuilding the trans is the best solution - could try draining the trans, flushing it out and refilling with new oil, and you might find it improves

Bill

replace the syncro rings. eventually you will not keep it in gear at all. probably when you are far from home.

Pretty common problem on any old trans. Disconnect the shift rod from the front lever on the trans. Move the lever back & forth. You should feel it snap when it goes into 2nd & 3rd & back to neatral. If it doesn,t the spring inside the cover is broken. If that,s not the problem than an o-haul is in order.

I drove mine like daily that till it grenaded about 1 year later. It picked a poor time and place to leave me stranded.

If you were ever thinking about doing that t-5 swap, now would be a good time.

Might it be your shifting fork? A worn fork will not allow the gear to engage all the way. Just a thought.
Good Luck
Steve

Thanks for the inputs. I replaced the fluid this weekend, but still have the problem. I guess you are right, and I might as well yank it out and go thru it. Seems like all the parts are available.

Snooky

It could also need the linkage adjusted,sometimes when the mounts get old the transmition could move a bit causing the linkage to come out of adjustment.My bet is on the sincros too tho.
Lothar

I also seem to have the same problem even though I welded some washers on bothe sides of the shifting levers to see if that might since the holes in the levers were elongated a bit? It helped some but not completly.Anyway sounds like I will be overhauling my 3 speed also.My question is where is the best place to purchase some overhauling parts for the 3 speed?

There is the occasional shift linkage adjustment problem or a bad bearing, but in most cases transmissions jumping out of gear can be traced back to misalignment.

I would also like to know where the misconception came from that syncros have anything to do with a transmission jumping out of gear. If you were to say the teeth in the syncro drum were warn then that would make sense and could cause a transmission to jump out of gear. The only job of the syncros is to make the meshing gears come to the same speed for engagement.

The Chevrolet shop manual talks about the need to align the transmission to prevent a transmission from jumping out of high gear. If the front and rear shafts are misaligned it will cause the shift fork and teeth to wear. A transmission may last a long time misaligned but it will cause damage and eventually fail.

I have made up my own tool to check alignment and have found that most transmissions need shimming to correct the alignment.

I can help any one interested with the alignment process.

is the brass ring the syncro ? If i remember correct,are they pressed in ? If that brass is worn,it will pop out of the gear drum, right or wrong ? I know the newer tranny syncros are different than the old ones.

The syncro is made up of a brass ring and a tapered steel cone. The brass ring is pressed in the syncro drum and the steel cone is held in with a snap ring. The steel cone and the brass ring can both be pulled out of the syncro drum in some cases.

What causes the syncro and the steel cone to pop out ?
Is it because the brass is worn that mates up to the cone ?
Years ago i had to replace the 2nd and 3rd syncronizer drum.I bought it from gm parts department,complete with syncros and cones.

Happy Thanksgiving...I would like some help on the alignment process. I did read that in the manual, but I wasn't sure what there was to align. Pre '68 Dave...I am interested in learning the alignment process. Thanks..
Snooky

Valley Gear and Transmission in Seattle has new ones. 206-329-5353

I was just thinking about the 1948-54 truck three speeds, they have a bushing that supports the front u'joint yoke. If the bushing is bad the main shaft will jump around and work the syncro drum off the main drive gear.

and if the thrust washer behind the 2nd gear is worn it will allow things to shift and pop the trans out of gear........
and if the needle rollers in the hub of the input shaft are worn , and the nose of the output shaft is worn ........ and ...... and ........

sure are lookin' at an o/haul.

Then get the reaglinement right and it should see you out...........

Say there Pre'68 Dave I'm interested in your tool for the alignment process.Thank You :confused:

i had a old chevy that poped out of 3rd for years put a long handle on it so i could keep my arm on it kept it full of stp. these trannys are all over the place for under 100. easy to replace instead of fixen

I had that problem with a '54 and found the rear support bushing (at the back of the trans for the u-joint ball to bolt to) was worn badly, a new one fixed the problem, after replacing the synchro drum didn't fix it. Mine had a heavy vibration as well as jumping out of 3rd gear.

Hey Buddy, I had that problem up to about 3 days ago. I replaced the synchro drum spent 1,500 trying to buy parts and have the guy fix this and that. I then relized that all the parts I was getting were used, they don't make these parts anymore. call patrick's and get you a 4 speed trans, eliminate all the frustration of trying to find those parts and make your truck perform better, now I love my truck and 4 gear is like overdrive. He has a kit that can allow you to retain your torque tube.