Question for the drive line Gurus.

[copterdoc]

Sorry if this is a silly question. Ok, I Recently converted my 1970 Chevelle (bought in 1984) to a ZZ502/T56 magnum combo. First hotrod manual I’ve owned. Everything is great, almost. I have a small stick vibration in 5th and 6th gear at 65 and above. Low frequency, more of a small rattle (not audible, just visual in the stick) not a buzz. Only see it in the stick not in the car or driveline feel. Used the TREMEC app to align everything. Final numbers in the pic. Is this normal? Am I over reacting? Should I try to sweeten up the driveline angles to zero? Can it be too straight? Any input would be appreciated.

[andrewb70]

Is the car lowered in the rear? Did you modify the trans tunnel to accommodate the T56?

Andrew

[copterdoc]

Car lowered 1 inch front, 1 1/2 rear. Short engine mounts, hooker 71222007 trans crossmember, tunnel cut out, patch welded in. Pics added to show rake. Slight nose low rake. Front wheel well openings 26 3/8” off ground, rear 27” 255/50/18 front tire (27”) 275/60/18 rear (30”)

[copterdoc]

Forgot to mention.stock springs all around, stiff Coil over spring shocks in rear, boxed control arms, UMI front and rear sway bars and rear frame connectors. All new polyurethane suppension and body bushings. Very little suspension and body movement. (For a 50 year ond car)

[andrewb70]

Are you sure it isn't the wheels and tires? From what you're describing the vibration seems to be more at wheel speed rather than driveshaft speed.

Andrew

[copterdoc]

Car is rock solid no vibration at any speed. Gear shift just bounces a little in 5th and 6th at high speed and low engine rpm. Beginning to think it’s a T56 magnum thing at low engine RPM. I have 3.31 gears and a 30 inch tall tire so 6th gear at 65MPH the engine is only turning 1500 RPM’s.

[andrewb70]

That big block is probably not happy at 1500 rpm with a carburetor. Might be better with EFI. Also, the timing at that RPM and load really needs to be dialed in. You can probably advance it quite a bit. The problem then becomes how to get the right timing when driving around town, etc...Another reason to go with EFI with timing control.

Andrew

[raustinss]

Or change cams lmao

[Get' er done]

Does the shifter stop vibrating if you get the engine rpm's over 2000, maybe 2200 while in 5th and/or 6th?

While I was researching a driveshaft purchase I spoke with a representative from "Inland Empire" at a Good Guys show and he mentioned to me that if you lug the engine while in overdrive there is some sort of harmonic generated with the T56 Magnum. He told me that he was aware of transmissions needing to have the overdrive gear section rebuilt from this condition after extended use while lugging the engine down. Maybe you can call Inland Empire or better yet one of the elite distributors of the transmission and see what they say?

[copterdoc]

Thanks. I think that’s what it is. I’ve just adjusted my shifting to keep the RPMs at 2000 and above and it’s all good.