nasty rear end vibration

[tdamon30]

I'm about 6 months into my 6 speed conversion and so far it's been awesome. I have been noticing while 100+ in 5th there is a nasty rear end vibration. I've ruled out tire balance, it's hard to explain its almost like a wobbling vibration.

Goes away after I slow the truck down to 80 or 90. I've crawled under the truck and nothing looks out of shape, loose or bent. Could the drive shaft I bought be out of balance or not true? Something in the rear end maybe? Or something wrong with 5th gear? I'm kind of stuck on what to look at.

Thanks for the help.

 

[Arska2]

Maybe its a matter of pinion angle ?

Shimming might be required.

 

[VPRPWRD]

if you shift to 6th and don't slow down does the vibration go away or remain constant.

 

[VENOMOUS1 RACING]

I'm about 6 months into my 6 speed conversion and so far it's been awesome. I have been noticing while 100+ in 5th there is a nasty rear end vibration. I've ruled out tire balance, it's hard to explain its almost like a wobbling vibration.

Goes away after I slow the truck down to 80 or 90. I've crawled under the truck and nothing looks out of shape, loose or bent. Could the drive shaft I bought be out of balance or not true? Something in the rear end maybe? Or something wrong with 5th gear? I'm kind of stuck on what to look at.

Thanks for the help.

I agree with Arska. Likely a pinion angle issue. Try to get it around -2 or 0

 

[tdamon30]

if you shift to 6th and don't slow down does the vibration go away or remain constant.

It does it in 5th or 6th. Haven't tried 100+ in 4th.

Scott,

Would I need to adjust pinion angle with the kit you sold me? Did you have to adjust yours or heard of anyone else having to do it running the 6 speed swap?

I did have to fabricate a rear transmission mount out of the existing because there wasn't one included in the l parts you sent me. Could that possibly be my culprit?

 

[VENOMOUS1 RACING]

It does it in 5th or 6th. Haven't tried 100+ in 4th.

Scott,

Would I need to adjust pinion angle with the kit you sold me? Did you have to adjust yours or heard of anyone else having to do it running the 6 speed swap?

I did have to fabricate a rear transmission mount out of the existing because there wasn't one included in the l parts you sent me. Could that possibly be my culprit?

The rear tranny mount remains. I sent the mount that goes onto tranny bottom itself. That piece mates to existing mount. Please take a pic of your mount when you get time.

 

[tdamon30]

Will do.

 

[nathanfreke]

I've the same issue. Mines between 85-100mph.
I've done the pinion angle and had the prop balanced.
Balancing the prop made a huge difference but the resonance is still there over a 15mph window.

Mine makes the noise / vibration under acceleration and deceleration.