ORD 4" Lift Drive Shaft Mod?

[caleb22]

Just took advantage of the ORD sale and bought the components to lift my 89 K5 4" (shackle flip, TC shocks, front kit). The salesman mentioned the need to check the driveshaft and maybe even go as far as to order a new one due to the vibrations and serious issues that would occur at high speeds.

What have others experienced? Is a new shaft or redo of the shaft in order on a 89 with a 4" lift?

 

[redneckdude]

I have 7" lift on mine with stock length shaft and my axle is actually a hair behind stock location...so yes it can be done, but i would not recommend it for one minute. I have very little slip left on mine and have grinded some to get it to not bind but i don't have any issues with vibes at any speeds. 4" would be a lot better for all driveline issues but your rear shaft shouldn't be too short. Getting it lengthened a little wouldn't be a bad idea tho...the main thing is just to set your pinion angle right which can be done with shims or a tapered zero rate...

 

[jms]

Just took advantage of the ORD sale and bought the components to lift my 89 K5 4" (shackle flip, TC shocks, front kit). The salesman mentioned the need to check the driveshaft and maybe even go as far as to order a new one due to the vibrations and serious issues that would occur at high speeds.

What have others experienced? Is a new shaft or redo of the shaft in order on a 89 with a 4" lift?

85, 2.5" flip + Zero rate (ORD), 3.5" total; I had some driveline vibrations after installing the lift, best solution in my case weren't the shims but dropping the t'case by 1 1/8". Also have a 1" spacer (Skyjacker, IIRC) on the front driveline at the t'case.

 

[GM Man]

Did the 4" shackle flip and didnt touch the rear drive shaft, no vibrations at all on mine.

 

[Leper]

It is a roll of the dice. Some trucks have to have modifications done. Some don't.

 

[78Suburban]

would a rear lift springs have a better chance of getting away with stock driveshats than the shackle flip? it wouldn't bother me to buy some shims, but I dont' want to get a cv rear shaft, because that's expensive.. I want 4" lift, but I surely don't want vibes or breakage problems, so I'm thinking I may go with rear lift springs, if that would help me keep the stocker.
thanks,
James

 

[dremu]

would a rear lift springs have a better chance of getting away with stock driveshats than the shackle flip? it wouldn't bother me to buy some shims, but I dont' want to get a cv rear shaft, because that's expensive.. I want 4" lift, but I surely don't want vibes or breakage problems, so I'm thinking I may go with rear lift springs, if that would help me keep the stocker.
thanks,
James

You'd be MORE likely to need a new shaft with big springs, IMHO, cuz your pinion angle will change. The flip generally points the axle up a bit more, so your existing shaft should work nicely.

-- A

 

[mouse]

You'd be MORE likely to need a new shaft with big springs, IMHO, cuz your pinion angle will change. The flip generally points the axle up a bit more, so your existing shaft should work nicely.

-- A

I think you have it backwards. The key to preventing vibrations using a stock driveshaft is to keep the angles of the u-joints the same at both ends of the driveshaft. When you angle the pinion up, the angle is reduced for the rear u-joint - made smaller than the angle of the u-joint at the TC. This WILL make vibrations (but protect the pinion when wheeling). It only takes a little over 1 degree difference to start noticing the vibrations. I've been there, done that, and bought the HAD CV driveshaft.

 

[Leper]

I think you have it backwards. The key to preventing vibrations using a stock driveshaft is to keep the angles of the u-joints the same at both ends of the driveshaft. When you angle the pinion up, the angle is reduced for the rear u-joint - made smaller than the angle of the u-joint at the TC. This WILL make vibrations (but protect the pinion when wheeling). It only takes a little over 1 degree difference to start noticing the vibrations. I've been there, done that, and bought the HAD CV driveshaft.

Mine was the opposite. It wasn't untill I pointed the pinion more up, did my vibrations go away. Right now my pinion points at the output of the tcase. Of all the people I wheel with, only 1 has the angles matched. Everyone else has the pinions pointed at the tcase.

 

[trailblazr81]

When I lifted a 81 K5 and 86 K5 with springs ang pinion angle shims I had vibes. Ended up using a longer CV joint shaft to get rid of all the vibes. Even with a longer shaft and 1350 U joints I had some vibes and u-joints werent lasting too long. Of course the 383 and 4.56 gears werent helping.

 

[ZooMad75]

When I did my shackle flip it pointed my diff up slightly more than what it had been sitting at. I had driveline vibes before the flip, and now I don't.

In my case the PO had 4 1/2" quasi (homemade) zero rates bolted to the spring pack. This caused the pinion to point down lower than stock, creating a larger difference in angles from the rear of the shaft to the front. It would eat the front u-joint in 6 months of regular driving. Post flip I havent had an ounce of any driveline vibe.

Each truck is going to vary, but I belive that the action of a shackle flip lowering the mounting point of the rear of the springs has a natural tendency to point the pinion angle in the positive direction. The whole axle and spring assembly ends up pivoting at the front spring mounts. So when you drop the rear mount down for a flip, the rear goes down but since it still bolted to the same location up front, the pinion rises. My truck needed a more positive pinion angle and benifited from this action, but that was with my stock 465/205 combo. Pulling the quasi-zero rates also helped too. Somebody else with a different t/case setup might need a different adjustment after a flip.

Measure your driveline angles before the flip and then after so you can tell if the angles got better or worse after the flip. All you need is a $10 magnetic protractor from sears.

 

[78Suburban]

According to the ORD website, the 4" lift actually overcorrects the pinion angle on burbs a little bit. because they have a longer wheelbase. So I guess a shim back down, or a zero rate could remedy that problem.

I just wish I had a definitive answer on what lift setup will let me keep my stock driveshaft with no issues.

thanks,
James

PS: Zoomad, do you have a pic of the prtractor you used? or does anyone else have a pic of a protractor appopriate for measureing driveshaft angles?

 

[redneckdude]

There is no definate answer. My 91 needed the axle shimmed back down and my angles match but lepers 91 has the pinion pointed at the t-case. His stepsons 70something didn't need shimming after the flip so it varies between trucks. You just have to mess around with it afterwards to get it right.

 

[ZooMad75]

Here is a pic from the Sears website. Look in the carpentry section.

Keep in mind, even if you have to make a slight pinion angle change either way, its still better than having to get the drive shaft modified with a cv.