I swaped out my rear end for limited slip with 372 gears on my 67 4speed 400. now have a strong vibration at 55 and up. put in a new balanced drive shaft and taken it to a specialty shop on drive trains and pinon angle is fine and every thing looks fine.Vib was'nt there before the swap. If I raise the pinon angle 6 degrees up the vibration goes away about 95 percent but i'm told thats in the wrong direction and it will tear out my pinon gear. they think it might be in my transmison. anybody have any thoughts before I tear out my tranny or worse. Thanks Joe

All other things being the same as before, it sounds like it's in the set-up of the rear gears. I've never personally done it but from everything I've read it came be a real tricky operation. I think I'd go there first. Pull the cover and check the mesh pattern. Just my .02

Robert

was your original rearend case used, and what original gear was in it?

If a different rear end, are you sure your driveshaft is the proper length?

You put in a new DS, so that answers the bad U-joint possibility. Did you do any work on the rear suspension, leaf springs or shock area?

I did all that last year and now have a new vibe that is prominent at 50-60 but is not present when above 60 or below 50. Just in that one speed range.

My best guess on my problem is that the new rear end parts have caused a previous problem in the tranny/engine area to become more pronounced now.

Hi guys everything is nem and put in by a shop that does them things and been double checked. there thoughts are like nashville 68birds and his problem sounds a lot like mine. It had a 246 gear non possie and from what I read it woud'nt except much of a lower gear so I put a 73 nova 12 bolt and had the mono leaf springs perches welded back on and have had them rechceked for angle and there fine every body seems to be mistified why its beter with the angle being way on the plus side for the pinon gear thanks for any help. Joe PS the factor bars that keep the rear end from rolling up to much, is there supposed to be much of travel to the?

After being absolutely sure its not tire balance, I would advise to get back with your driveline shop to see if they can help with your angles. Pinion angle as well as transmission mount height will need to be considered. I'm not saying the angle IS your problem, but it is VERY critical.

Sounds like a loose pinion bearing to me. If you change the angle and the noise changes you are close. Maybe using the higher angle puts enough pressure on the pinion bearing to quiet it down.