Launch drive-train shudder!

[76chev454]

I have a 76 C10 with original 454 CID bored 60 over.  Axle is 12 bolt 3.42 or 3.43.  Not real sure of that.  Lots of goodies in the engine including roller lifters L5 heads and the like.  Full hooker headers.  Plenty of torque and power when needed.  I am getting ready to put a new bed in and after I took the old bed off, I noticed the driveshaft angle to the rear axle is not straight.  Asked a tranny guy about it and he said it should be straight.  So, that is probably where the shudder is coming from at low speeds.  Do not have it after about 35mph.  -- Am enjoying the discussions.  Thanks for all the input.

[ccb]

If its not wheel hope, them the manual tran pressplate is warped or both.
Put there only guess with out seeing it.
Craig

[76chev454]

No Craig, wheels are not hopping!  I have added a system similar to CalTrec.  Works very good.  Driveshaft did not cause problems before trans was rebuilt.  Any ideas about driveshaft alignment?  How could it come out of alignment?    

Professor of Interesting Stuff!

[ccb]

What has change from the last trans you had? What is diffrent? I think that where I would start. Is everything in the same place. Did you mark everthing be for you removed it?
So you could put it back in the same place. is everything lined up?

Craig

[roundedline]

76chev454
What do you mean the driveshaft is not straight?  As in it has a bend in it?  Or it doesn't run parallel to the frame rails?

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[76chev454]

From the yoke to the axle, it is not parallel to the frame.  I do have shims that I could install.  By the way, at about 20 mph, no vibration is noted.  

[roundedline]

You are talking about from the output yoke to the axle input yoke.  This isn't supposed to be straight parallel to the frame.  It will be angled some.

Drivetrains centerlines must be parrellel in all respects.  Due to u-joints nature the operate best at an angle.  As long as the crank centerline and the pinion centerline are parallel you are ok.

Chris Lucas
www.73-87chevytrucks.com
www.captkaoscustoms.com
Project Su
Jimmy 2WD Project

[ccb]

Its hard to give ya help with out see it. Chris said it best,
I think my question is still what has changes from the last trans? I assume you have a GM repair manual that tell ya how every is set up. I think there a formula for setting up the drive train I saw one in one of the truck web sites. If everything else check out I would say It may be worth a trip to rear end shop to see if some thing came loose.

Craig