onebadbowtie86

iTrader: (13)

Thank you so much launch, I think I'm getting it. I had my car set up like the second picture, parelel. No I'm setting it up so pinions pointing down instead of up.

Launch

Leave the transmission as is at 3 degrees. Now just adjust your rear axle so the pinion is pointing down, rather than upwards, and then drive the car....

Launch

Yes I think it will fix your vibration. If not then you need to assume there's something out of wack with your rear end or the transmission itself, rear end is always more likely

onebadbowtie86

iTrader: (13)

Right now the trans is pointed down 3.5 and pinion is down 2. The vibrations still there, but it moved it higher in the mph it feels like. Should I try putting the pinion back up to 0 or lower it even more to -3 or -4?

Launch

Im outta ideas man. Without seeing it in person I can't get a grasp of how your driveline angles are exactly. You could try point the pinion down further but im starting to think the issue is elsewhere. What rear axle do you have? And how old is it?

Sure it's not rear wheel balance issue?

onebadbowtie86

iTrader: (13)

The rear axle is a gm 8.5" with new moser axles, new bearings and a trutrac. 4.30 motive gears. I just pulled the diff out to install the new 1350 pinion yoke and set the pinion pre load. everything in the rear appears good? I ran it on jack stands with now wheels tires or brake drums with no difference.

I guess I'll just spend some time moving the pinion around tomorrow.

onebadbowtie86

iTrader: (13)

I don't think my vibration is a driveshaft/pinion angle issue. Just tore into my t56 and I have the loose 5-6 gear on the main shaft. Thank you everyone for the help.

Launch

Hopefully that fixes it. Driveline vibrations and other difficult to diagnose problems can be frustrating as hell. I've had a good run so far with all my vehicles and not had any vibrations.

My tire shop couldn't even balance my Weld wheels because they didn't have the proper 5 lug attachment to clamp them down for balancing, they didn't understand how these wheels should be balanced, they were spinning them up and telling me they're bent as **** and to send them back, but I read the Weld Racing instructions and I knew the tire place don't know wtf is going on.. So I just took them and ran them on the car as is and without any balancing my car still feels 100% winding the speedometer right over.

If you repair your T56 and still have the vibration, all it could be left is something wrong with your pinion yoke, maybe it's been machined off center.. you never know these days. Personally I'd only run either a genuine Spicer, or a Strange or MW chromoly pinion yoke.

onebadbowtie86

iTrader: (13)

Ya, this driveline vibe has been frustrating to say the least but I think This is the problem.

I dont think the pinion yoke is bad, I had a new spicer on my 8.5" when I rebuilt it a year or so ago, and I just installed a chromoly strange 1350 pinion yoke with no change.

Mike Blanco

I don't want to hijack, but saw this post was from back in Feb. So I think I might be having the same issue as Bowtie. My trans tail is point -4 down while my pinion is +4 degrees. In my head I thought this balanced things out with a 0 degrees. However, after reading this post I am doubting my setup. So according to Launch I need to have both my tail shaft and pinion in the negative. Then most optimally have my pinion at -2 or so to account for pinion wrap up?

If that is the case then that is what I will try. However, I am running a non adjustable 4 link, and not sure how to make the proper adjustments that I might need. Any help is appreciated.

DANSBIRD

iTrader: (2)

Forgive my ignorance here, but what all components and aspects are taken into consideration when picking out/choosing a driveshaft? I've seen 3", 3.5", steel, aluminum, carbon fiber, the weight of the car, etc..

Why are some drive shafts not recommended for street cars?
Would spinning around a steel DS be noticeably slower/more work than aluminum or CF? Or is that mainly splitting hairs for true track cars and not a consideration for street cars?

Sorry for the loaded post. Just curious about the world of drive shafts.