driveshaft

[Mr.Supersonic]

Hi everyone. I have a 68 c10 longbed. it currently has the small diameter 2 piece driveshaft. I'm going to be swapping the engine & transmission soon. (I know I've been saying that for a while but it really is gonna happen soon) I was wondering if I should replace the driveshaft with one from another vehicle, or an aftermarket unit? I want to stay 2 piece because that is probably to long for a 1 piece. any thoughts? thanks!

[LH Lead-Foot]

What are you putting in for engine & tranny?

I am sure if you asked a drivetrain expert, they would tell you to go one piece. You don't have to deal with support bearing, plus 3 other u-joints. I'm sure there a few locations that will do this for you...for a price.

I am used a 1 piece drive shaft from an 03 Tahoe. It is steel and slightly larger diameter compared to the OE 67. It has the same 27 spline slip yoke that fits my 1987 700R4 behind a 5.3L "LS" motor. The u-joints are larger but few 50 year old trucks would not need newer u-joints.
A little research let me find the Tahoe is 3150, while the OEM 1967 is a 3110
(I think the numbers are right, but double check them by measurements and online charts)

Always mark the location of the yoke's centerline before cutting off to reference proper location.
I cut the yoke flange (Companion Flange) off at the weld, cut shaft to length, cleaned, ground an angle on cut edges and welded. I had help with "Tee Notch" jig and someone to turn the shaft slowly as I welded it with my 1984 MIG.
(This MIG is huge with it own cart, tank ledge and handle. 155 amps and hold the 14" spool) New ones are real small. Maybe that's why it's still working.

Afterwards, I install a conversion u-joint that is 3150 on one side & 3110 on the the other. Oddly enough, it's OEM on the 1988 - 1999 Camero and Firebird and commonly available. I got mine from RockAuto for $7 from spicer.

As far as balancing, you can use the GM factory service manual trick, using two worm-drive hose clamps mounted at the back, then rotate together to find the sweet spot. Just make sure they are one clamp, even if you have to buy two that a large enough to fit.

If you safely support the vehicles rear axle with stands, blocks on the front, these clamps will quickly find balance as it will not take much for them to vibrate the ale & frame. Just leave the clamps loose enough to move, so you can do this in 15 minutes. Tack weld two washers for 5/16" bolts where the clamps land.

It's a two page process in the GM service manual. I got lucky & didn't need anything added to balance.

[Mr.Supersonic]

Originally Posted by LH Lead-Foot

What are you putting in for engine & tranny?

I am sure if you asked a drivetrain expert, they would tell you to go one piece. You don't have to deal with support bearing, plus 3 other u-joints. I'm sure there a few locations that will do this for you...for a price.

I am used a 1 piece drive shaft from an 03 Tahoe. It is steel and slightly larger diameter compared to the OE 67. It has the same 27 spline slip yoke that fits my 1987 700R4 behind a 5.3L "LS" motor. The u-joints are larger but few 50 year old trucks would not need newer u-joints.
A little research let me find the Tahoe is 3150, while the OEM 1967 is a 3110
(I think the numbers are right, but double check them by measurements and online charts)

Always mark the location of the yoke's centerline before cutting off to reference proper location.
I cut the yoke flange (Companion Flange) off at the weld, cut shaft to length, cleaned, ground an angle on cut edges and welded. I had help with "Tee Notch" jig and someone to turn the shaft slowly as I welded it with my 1984 MIG.
(This MIG is huge with it own cart, tank ledge and handle. 155 amps and hold the 14" spool) New ones are real small. Maybe that's why it's still working.

Afterwards, I install a conversion u-joint that is 3150 on one side & 3110 on the the other. Oddly enough, it's OEM on the 1988 - 1999 Camero and Firebird and commonly available. I got mine from RockAuto for $7 from spicer.

As far as balancing, you can use the GM factory service manual trick, using two worm-drive hose clamps mounted at the back, then rotate together to find the sweet spot. Just make sure they are one clamp, even if you have to buy two that a large enough to fit.

If you safely support the vehicles rear axle with stands, blocks on the front, these clamps will quickly find balance as it will not take much for them to vibrate the ale & frame. Just leave the clamps loose enough to move, so you can do this in 15 minutes. Tack weld two washers for 5/16" bolts where the clamps land.

It's a two page process in the GM service manual. I got lucky & didn't need anything added to balance.

i want to keep the 2 piece because it is a long bed, and it will be too long for a 1 piece. I'm putting in a 400/700r4 replacing the 350/th400. i just want to get rid of the small diameter shaft i have because this new motor is going to be putting out close to 400hp and I'm worried it will break it, plus the small diameter shaft has a pretty low critical speed from what i read, like 90 mph or something like that. i just want to minimize weak points.

[LH Lead-Foot]

My 67 C10 has an LS with 368 HP, one piece drive shaft, 700R4, Tahoe drive shaft, 3:08 final on 245R75R15, works great with center crossmember, ran up to 119 MPH on interstate North of Salina KS.

[rjs53]

I just replaced my 2 piece with a single. ( shortened truck from long bed to short) However the shop I went said one thing you have to watch out for is to long of a single driveline and it can get a whipping affect sometime. I'm sure other she may have a different opinion, but it sounded good. I don't know what the issue would be with using bigger diameter tubing

[LH Lead-Foot]

I agree rjs53, But that type of phenomenon would be caused by two different problems.
One is the wall thickness of the metal used in the driveshaft tube itself. When aluminum became popular (Reduced Weight for CAFE #'s), the outside diameter increase noticeably.

Two is the length of the tube, thus resulting in flexing. This problem can not be solved by balancing, but a shorter stiffer tube, properly balanced would correct that issue. From school busses, farm trucks to stretched limo's will require multiple drive shafts.

I would prefer to keep it simple. If there are no issues with a factory designed 2WD Tahoe 4DR driveshaft, shortened about 2 inches, worked fine for me. I was almost convinced that it would fit without having to be shorted, but didn't work out that way. Motor mounts, distance from radiator, bell housing bolt access, headers, etc. all created factor in the application.

I was concerned the crossmember would be an issue with the rear axle off the ground...hanging, but wasn't even close.

I have never seen welded weights on the front, always on the back.
But I would not be surprised to find some factory drive shaft with weights on the front & back also. Just never seen them while servicing a U-joint or pulling at trans or diff repair.

But I am not the engineer and the subject never come up while in Troy, MI.I am sure there is a limit to length that is always factored in, regardless of material.