GearVendors install 67 Coronet

[Mackman]

I just finished the installation of a GearVendors overdrive in my 67Coronet R/T. 500 stroker with a 727, 3.23 axle with 26" tires. It went as expected per their install instructions, other than I had to dent the tunnel more than they described. I have stock manifolds with an Accurate exhaust system. Had to make extensive modifications to the exhaust. Pipes on both sides hit the OD unit, as did the H pipe. I cut both pipes at the trans crossmember to keep them farther apart, cut in a new H pipe, and offset both pipes back to the original muffler location. Instead of cutting my original driveshaft, I had a new shorter shaft made up at a local driveline shop.
I'm happy with the results in operation, but I have a slight vibration in the driveline that starts at about 65 MPH and stops at about 72 MPH. Doesn't matter if it is in OD or not. I assume it's because of the change in driveline angle?

 

[Kern Dog]

It could be.
I had a GV in my Charger over 10 years ago and had vibrations too. I never figured out what it was. I pulled it, went back to a 727 then….swapped to a Tremec 5 speed 4 years ago.

 

[Mackman]

It could be.
I had a GV in my Charger over 10 years ago and had vibrations too. I never figured out what it was. I pulled it, went back to a 727 then….swapped to a Tremec 5 speed 4 years ago.

The aggravating thing is it was as smooth as glass before. I went to the OD because we drive the Coronet a lot of highway miles.

 

[TorRed]

I have a Gears Vendor unit to go in the bird, I'll be interested to see if you're able to track down your issue, hopefully without pulling the O/D. Good luck.

 

[Kern Dog]

For me, the cause was a mystery. There were enough mistakes to have Collectively added to a problem. The prior owner of the GV I had ran it without oil and had it rebuilt. Who knows if it was done right. I had the drive line angle wrong. I know this because the prior owner supplied a crossmember that put the tail shaft too low. I’d heard that the drive line tunnel had to be dimpled for clearance but mine cleared by over an inch. The drive shaft I used a slip spline line used in the front of an old 4 wheel drive truck. This was because he kept the fixed yoke on the rear of the GV unit instead of a splined output shaft. I didn’t know that it unbolted or I would have had a better drive shaft made.

 

[dan juhasz]

did it change your driveline angle? I'd lean to a not perfect balance job on the new driveshaft