Short bed K10 driveshaft angles

[68isgreat]

I know driveshaft angles have been discussed before, but here's my dilemma:

I have a stock height 68 K10 shortbox stepside that had a 6 cyl/4sp from the factory. After installing a crate tbi 350 in the rear position, and a rebuilt 700r4/241c combo (which I know is a lot longer than the 6 cyl/4sp) and having a new rear driveshaft made, the shaft is only 38" long, resulting in a steep 16 degree driveshaft angle and 12 degree working angle at the xfer case (set at 4 degrees) and 9 degree working angle at the pinion (currently set at 7 degrees). If I drop the pinion down to 4 degrees to match the transfer case, I'll have a driveshaft angle in the neighborhood of 19 degrees and U joint working angles of about 15 degrees. Ouch. From what I've read, unless I want to be changing out u joints every few months due to the steep angles, I should probably raise my pinion up to point at the xfer case and go with a SYE and double cardan shaft, and drop another $1k down the rabbit hole. I should probably just call my truck a boat, short for "bite off another thousand."

What I don't understand is, how were these short bed K10's, and even the later OBS short bed trucks, set up from the factory and how did they avoid these steep angles? They didn't have double cardan rear shafts, or rear pinions angled up 15 degrees. An OBS truck (which came with the r4/241c combo) wheelbase is only 2" longer than my 68. I feel like I'm dealing with lifted truck issues, and my truck is only stock height. I must be missing something very basic here. Something doesn't add up???

[pjmoreland]

I have a 1989 K1500 shortbed with the stock 350/700R4/NP241C drivetrain and stock ride height. The operating angles of the rear driveshaft are 3° down in the front and 3° up in the rear.

I also have a 1971 K10 shortbed that I am in the process of getting back on the road. I installed an NV4500 transmission and an NP205, but I slid the engine forward 2" to keep the transfer case in the stock location. My rear driveshaft operating angles currently are 6.7° down in the front and 2.7° up in the rear. I believe these angles would be the same on a factory original truck, but I have changed some things, so my angles might be a little bit off. The rear driveshaft is 49" long, center-to-center.

[68isgreat]

Originally Posted by pjmoreland

I have a 1989 K1500 shortbed with the stock 350/700R4/NP241C drivetrain and stock ride height. The operating angles of the rear driveshaft are 3° down in the front and 3° up in the rear.

I also have a 1971 K10 shortbed that I am in the process of getting back on the road. I installed an NV4500 transmission and an NP205, but I slid the engine forward 2" to keep the transfer case in the stock location. My rear driveshaft operating angles currently are 6.7° down in the front and 2.7° up in the rear. I believe these angles would be the same on a factory original truck, but I have changed some things, so my angles might be a little bit off. The rear driveshaft is 49" long, center-to-center.

Thank you very much. How long is the driveshaft on the 89? The one on your 71 is 11" longer than mine, which must be how you're able to have a 2.7 degree angle in the rear. I talked to Woods Driveshafts, and they said to drive mine like it is first and see if there is any vibration before changing anything. I haven't driven it yet, but the angles just seem extreme.

[pjmoreland]

Originally Posted by 68isgreat

Thank you very much. How long is the driveshaft on the 89? The one on your 71 is 11" longer than mine, which must be how you're able to have a 2.7 degree angle in the rear. I talked to Woods Driveshafts, and they said to drive mine like it is first and see if there is any vibration before changing anything. I haven't driven it yet, but the angles just seem extreme.

The driveshaft in my '89 is 41" long.

[68isgreat]

Originally Posted by pjmoreland

The driveshaft in my '89 is 41" long.

Hmmpf. Apparently that extra 3" length really makes a difference. That's what she said. Lol.

[pjmoreland]

Both my K10 and K1500 have stock suspension, but the K10 sits significantly higher than the K1500. I'm guessing that's a big part of the equation.

[68isgreat]

Originally Posted by pjmoreland

Both my K10 and K1500 have stock suspension, but the K10 sits significantly higher than the K1500. I'm guessing that's a big part of the equation.

Ahhh. I wasn't aware of that. That makes sense now. Appreciate your help.

[HO455]

If after testing your vibration free run it. Just be aware that you will experience short U-joint life span. Keeping things greased will help some.

The greater the angle the more vibration is generated due to the how a U-joint speeds up and slows down on every revolution. A constant velocity joint is the cure for that kind of vibration.

https://youtu.be/LCMZz6YhbOQ?si=vhNn4XQAqiyfh4T5

https://youtu.be/FTiJAdJjsqA?si=nVMzbwPJ-a6Bcm-2

You might give I-5 driveline in Vancouver a call and talk to the owner, he's an old guy who's done it all.

Good luck neighbor!

[68isgreat]

Originally Posted by HO455

If after testing your vibration free run it. Just be aware that you will experience short U-joint life span. Keeping things greased will help some.

The greater the angle the more vibration is generated due to the how a U-joint speeds up and slows down on every revolution. A constant velocity joint is the cure for that kind of vibration.

https://youtu.be/LCMZz6YhbOQ?si=vhNn4XQAqiyfh4T5

https://youtu.be/FTiJAdJjsqA?si=nVMzbwPJ-a6Bcm-2

You might give I-5 driveline in Vancouver a call and talk to the owner, he's an old guy who's done it all.

Good luck neighbor!

Nice, thanks neighbor! I probably will go the double cardan route at some point. I don't want to be worrying about u joints going bad even if I don't feel any vibration. Do it right the first time...