One piece driveshafts.

[Terakilla]

Just got my new gen II motor in, which has a 4L60-E trans. The old driveshaft will fit it buy it needs to be cut and I'd rather use the new driveshaft that came with the engine. I've already scooted the motor back the 2 inches needed for it to be long enough and a conversion u joint will be easy to get. The prob it the hole in the cross member where the carrier bearing mounts. The new shaft it 3 inches round and fits in the hole fine, and I plan on lowering the truck anyways so the rear end won't have as much travel. Does anyone know of any issues with this, I don't wanna damage anything

[BP68]

Is the old driveshaft one piece? I am running a 700r4 and had the driveshaft from the suburban it came from, but it was a little large. I ended up having the yolk from the suburban installed on a cut down one piece lwb 72 truck driveshaft. Works and fits great even with a 4/6 ece drop. I just removed the carrier bearing bracket from the frame.

Also, ECE sells a lowered crossmember that has a offset in the center hole for lowered trucks.

Hope this helps.

[Terakilla]

The orig driveshaft has 3 u joints, 1 at trans, 1 at bearing, and 1 at rear. It's really small dia at around 1 1/2 in. The new one only has 2 u joints at each side and is 3 in. I haven't seen a single strait shaft from trans to rear on these trucks, sort of a newb. I think I can cut some of the cross member easy. Maybe I won't have too much trouble.

[unclewatts]

Like you I have a two piece driveshaft. Some time ago I talked to a reputable mechanic about swapping to a one piece driveshaft and he said that it's too long to balance it for it to be reliable. He also said that it puts to much stress on the bearings at each end as GM never intended those bearings for a single driveshaft. Later on through someone's recommendation, I called Driveline Specialties in Sacramento and the guy on the phone said no problem they could custom fab one up for me for about $600. I know that this doesn't directly answer your question but it does show that it pays to ask around. BTW, I never did do the changeover and my old driveshaft still works great.

[yote1234]

i replaced my 2 pc with a 1 pc in my shortbed with no problems.. been about 10 months..

[BB72CHEVKT]

I have gone to a one peice shaft in both trucks. I had both made for under $200.

[Longhorn Man]

why not stick with the 2 piece? It's stronger and helps with the driveline angles.
Its a better set up

[Terakilla]

Thanks for the input, I always heard a one piece hollow bigger around shaft was better. To use the old one I woulda had to cut, weld, rebalance it whereas the new one just scoot motor back 2 inches. Plenty of room to scoot both ways and elec fans so no prob there. New trans is now about 1 foot farther back than old 3 on tree, all electronic auto and all. I just need to figure out the total travel of rear end and make sure the driveshaft won't hit the walls of the hole in the crossmember that the trailing arms mount to. Less moving parts the better they say.

[jamis]

I run a one peice and have never had a problem and I think any driveshaft shop that tells you it can be a problem is full of it.

[Longhorn Man]

no, actually the oposite is true. Many driveline shops that say they can... shouldn't.
Once a driveshaft gets close to 6 feet long, 'whipping' becomes a problem. Whipping, when talking about drive shafts or prop shafts is in reference to the shaft actually sagging from it's own weight and then traveling in an arc rather than a spinning shaft, an exadurated example would be picturing a jump rope being used.

The best way to get around that, is to build a lighter shaft. However, to do that, they have to be very large in diameter. With the crossmember that has a small hole in it, that becomes a problem. you have to limit the rear suspention travel in order to do it. (hey, less moving parts, must be better)
The long aluminum shafts are not known for there strength. We replace them at work (with steel ones) fairly regularly. They twist like a twizzler.

With a carrier bearing, you get strength through a short shaft, and flexability through a U joint in the center that lets the shaft go in 2 seperate angles.
This has been done since the factorys got away from the torque tube rear suspention in everything from passenger cars to big rigs that put out mega torque.
It' a better design as long as you don't use junk parts.

[unclewatts]

Hey Longhorn man, how'd you get those kitties to pose like that? I could never get my cat to do that!

[Terakilla]

I saw some pics somewhere of a gut installing tubuler trailing arms and c notches and seem to remember a big driveshaft. As long as the shaft won't hit the crossmember ill be cool. New motors not gunna have much torque, aiming for a highway driver and not a rod. Shafts only like 4' long. Gunna have to remove more rivets holding the hearing mount, no prob.

[toddtheodd]

Oh for the love of god...
I will go take a picture of mine today and have the mods make it a sticky or something just to end all these questions about 1 piece mythical driveshafts.
I have one in my long bed behind a th350 which was dropped 2 inches all around. It was 1/4 inch shorter than the longest they would guarantee, and I have not had a problem with it.

[Terakilla]

Awesome, I have no more worries, now I can proceed as ussual.

[spyder4560]

Don't want to be a post hijacker,but thought I'd put in my two cents worth.I've got a '69 GMC 3/4 ton with a built 400 Pontiac engine,400 turbo with shift kit,straight driveshaft from the donor Catalina with a conversion u-joint in the rear.This thing has tons of torque and I 've never had to replace a u-joint in almost ten years of owning this truck.I haul cars and trucks all the time on my trailer.Just my opinion that one less u-joint is one less headache.

[Ackattack]

I looked under my 05 crew cab silverado, and it has a large diameter aluminum drive shaft that is probably 6 ft long.

As you go longer, you should go with a larger diameter.

[toddtheodd]

Originally Posted by spyder4560

Just my opinion that one less u-joint is one less headache.

The whole reason I went with a 1 piece drive shaft was because my carrier bearing and ujoints were bad... and it was cheaper to have 2 ujoints replaced, and a custom driveshaft made, than it was to have all 3 ujoints replaced and the carrier bearing replaced.

Crazy right?

I guess when you buy a driveshaft, the ujoints are thrown in for free.

[westofb]

Originally Posted by Longhorn Man

why not stick with the 2 piece? It's stronger and helps with the driveline angles.
Its a better set up

I myself have had 2 of the slip yokes on the 2 piece drive shaft fail. They both busted in the splined area length wise...rear drive shaft fell out contacting the ground...luckily there were no large chug holes for them to fall into. Switched to a one piece, no more porblems since.

[Terakilla]

Seems one piece shafts are more reliable, or they'd still use two piece. Was told that skinny driveshafts will twist way easier than hollow big ones, something about surface area.

[texanidiot25]

Most of the time it is not reliability but cost effectiveness that changes how things are made. Heavy dudy (talking medium duty and up) still use 2 piece styles like our trucks. I'd wager those know a tough design better than any modern half ton.