Shifter Shakes Only in Third Gear And Only When Accelerating

[Jack O.]

Just got my '69 back together - rebuilt the trans, new clutch and pp/flywheel (balanced together), new u-joints, driveshaft assembly balanced - and everything seems good except my shifter shakes only when in thrid gear and only when I'm accelerating. Shifter is bolted to crossmember as original. No shaking at idle in neutral and the shaking is limited to the shifter - nothing felt in the driveline itself or in any other situation. I don't think it's the shifter because it didn't do it before I did this recent work. I haven't driven enough to really debug it further and have only took a quick look underneath for any obviousily loose mount points but didn't find anything. Figured I'd ask here before looking further because it seems like something someone has encountered before. The shaking isn't that bad but since it didn't do it before I know something is not right. Anyone have any ideas? Thanks!
Jack

[Jack O.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Could the tranmission mount cause this? I would think that if the mount was bad I'd have other vibrations. I'm hoping it's nothing to do with the trans itself since I rebuilt it myself and it's the first one I've ever done. I need to test drive the car some more but the weather is making that difficult!

[Paul J.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Jack, there are some threads in the archives about this. First, you have to determine which side of the clutch the vibration is on. Get the car/rpms up to the speed where the vibration is and push in the clutch. If it stops, then it could be on the engine side. If it continues, then it's on the drivetrain side. It could be in the transmission, driveshaft, u-joints, etc. You'll have to start eliminating things, but you're right about having to drive it to do this. First, check out the archives.

Paul

[Edward J.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Jack, Do you hear any gear noise when in third gear? or anything that does not sound correct while driving in third gear normally? I am leaning toward transmission since you don't have any issues with other gears. Problem such as thrust bearing, or snap ring issue.

[Jack O.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Thanks Paul. We're snowed in now but hopefully it will clear up enough for me to drive. I changed a lot of things so it really opens the realm of possibilities. I was hoping the fact that it only does it in third gear would eliminate some of these. I did check the archives before I posted but will go back and check again since I was surprised that I didn't get more hits.
Jack

[Jack O.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

No unusual noises and shifts great up and down. It was a short test drive but everyhting else operated great. The vibration is limited to the shifter - when I hold the shifter firmly it stops and there is no other vibration. I'm hoping it's not the trans but it has me the most worried since it's the first one I've ever rebuilt. I checked with Paul Cangialosi of Medatronics (trans guy) and he thought it was more likely to be mount related but did say "...only other issue I can think of is if the slider and hub are really loose and for some reason rattle internally when in that gear. Its possible, but rare". Thanks for the help.
Jack

[Jack O.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

I didn't find any threads that matched my issue real closely - only vibrates in one gear, only when accelerating and limited to the shifter.

[Jim T.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Jack there is a reprint of Technical Service Bulletin on the back cover of the Winter 2014 Corvette Restorer that is about 4-speed shifters. It has been to long since I removed my 68's shifter to remember what components are involved compared to what is in the bulletin.

[Paul J.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

I didn't find any threads that matched my issue real closely - only vibrates in one gear, only when accelerating and limited to the shifter.

Try some of these, remember that some of the same problems cause slightly different symptoms in different cars.

https://www.forums.ncrs.org/showthre...ight=vibration

https://www.forums.ncrs.org/showthre...ight=vibration

https://www.forums.ncrs.org/showthre...ight=vibration

https://www.forums.ncrs.org/showthre...ight=vibration

https://www.forums.ncrs.org/showthre...ight=vibration

https://www.forums.ncrs.org/showthre...ight=vibration

This is a sample of discussions on several different problems. There's a lot more of these. My search focused on "vibration".

Paul

[Jack O.]

Re: Shifter Shakes Only in Third Gear And Only When Accelerating

Thanks Paul.