Trans/Pinion/drive shaft angle

[68GMCCustom]

I've had a bear or a time trying to get a vibration my truck has since the rebuild. Its gone from bad to a little less then bad after being all over the map. It busted a pinion ujoint a while back and while it held together enough to limp it home...it was vibrating real bad, limiting speed to 25-30mph or so. Tho I had some measurement errors along the way....its all 3-3.5* now.

All that said, I read something recently that said for high speed vibrations the driveline angle should be dropped from 3* to 1*. I looked under our TBSS and the trans yoke looks to be a few degrees and the pinion looks more like 0*.
My question is, has anyone here had to bring their trans and pinion yoke angles down to 1*? Or close to it?

[contagious102]

If i remember right,set them at -2 degrees at race weight.When the truck or car is under power the rear end is trying to climb up the ring gear,lifting the pinion up.If you are starting at +3,when you gas on it,it could go as high as +5 or 6 degrees.

[68GMCCustom]

I've heard that for leaf spring setups...but even with truck arms?

[Marv D]

Check this page out

http://markwilliams.com/driveshafttech.aspx

If you are sure your yokes are phased correctly, and you have the angles the same when under way.... I'd have someone check the shaft balance... and dont overlook the possibility of the horizontal centerlines being different causing higher angles than you measure vertically. I made that mistake in a build 'assuming' the engine/trans centerline was centered in the chassis,, ordered a rear that set the pinion in the center of the frame rails.
WRONG,, there was over 1-1/2" as I remember the engine was shifted to the passengers side. With a short shaft this starts making BIG angle differences if you don't set the pinion centerline the same offset.

I've used these guys for a couple of shafts,, pretty economical for what you get and so far i've had 0 problems with fit or reliability. Just be SURE and get every measurement they ask for in the order form.
http://www.dynotechengineering.com/

[68GMCCustom]

Had good luck with my shafts builder in the past...but maybe I should look into ordering one from these guys. I guess if I ever got fast enough for drag week an extra d-shaft wouldn't be a bad thing to carry along.

I guess I need to recheck everything...thinking I may have to go to the larger hump for my 4L85e after all...to get everything right.
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[RICKSRAT]

Had a new driveshaft built last year from here. Close to you and 48hr build time.
http://www.driveshaftspecialist.com/...itroShaft.html

[68racer]

Where can I get shims that fit the trailing arms? I've modified normal ones but I would like a better fit.

[68GMCCustom]

I can help with that...found them a couple of places. Bought some DRP's for ease of use.


store.drpperformance.com/PINION-SHIM%3B-TRUCK-ARM



stockcarproducts.com/trkarm