Carrier Bearing

[Pinger]

My crew cab has the two piece driveshaft, but considering it has a 168" wheelbase,

More than three feet longer than a Suburban's lengthy 130'' WB! I knew CCLBs were longer in the WB than 'Burbs but not by that much.

it pretty much has to!

Yep, I see it now.

 

[Schurkey]

Far as I know, the issue is more driveshaft length, than driveshaft load.

The driveshaft resonates/flexes at a frequency dependent on length, material, wall thickness, and diameter. Short driveshaft flex frequency is higher than long driveshafts, steel is different than aluminum or carbon-fiber, and a large diameter flexes less than a small diameter.

Driveshaft Critical Speed

Calculate Driveshaft Critical Speed - by Wallace Racing Home of Pontiac Powered Firebirds,Trans Ams,Pontiac Powered Dragsters,Pontiac Power Rules!

wallaceracing.com

The idea is that the driveshaft flex "critical speed" has to be higher than the vehicle will ever spin that driveshaft. So instead of one long and whippy shaft, they go with two shorter shafts. Look under an old front-engine school bus sometime--they've got more driveshaft segments and carrier bearings than you can shake a stick at.

This is also why longer vehicles generally end-up with longer transmission housings/tailshafts--to shorten the driveshaft length to something manageable. Cadillac TH400 transmissions had the longest tailshafts of all, full-size cars got the next-longest, and compact/intermediate cars got the short tailshafts.

Although the stresses are different, the things that make a good driveshaft also make a good pushrod--material, wall-thickness, diameter, length, etc.

 

[HotWheelsBurban]

More than three feet longer than a Suburban's lengthy 130'' WB! I knew CCLBs were longer in the WB than 'Burbs but not by that much.

Yep, I see it now.

Basically a Burb has a 5' cargo space after the first two rows of seats. Crew cab long bed has 8' of cargo space behind the seats, so there's your extra 3 feet! The whole truck is almost 22 feet with the brush guard on the front and the trailer ball mount in back. I leave it in so I have something to step on, getting in and out of the bed!
The square body Burb had a 129" wheelbase which is 2" shorter than the single cab long bed pickup. When the 400 Burbs came out in 1992, their wheelbase is 131" like the single cab long bed pickup, but the frames are different.

 

[HotWheelsBurban]

Far as I know, the issue is more driveshaft length, than driveshaft load.

The driveshaft resonates/flexes at a frequency dependent on length, material, wall thickness, and diameter. Short driveshaft flex frequency is higher than long driveshafts, steel is different than aluminum or carbon-fiber, and a large diameter flexes less than a small diameter.

Driveshaft Critical Speed

Calculate Driveshaft Critical Speed - by Wallace Racing Home of Pontiac Powered Firebirds,Trans Ams,Pontiac Powered Dragsters,Pontiac Power Rules!

wallaceracing.com

The idea is that the driveshaft flex "critical speed" has to be higher than the vehicle will ever spin that driveshaft. So instead of one long and whippy shaft, they go with two shorter shafts. Look under an old front-engine school bus sometime--they've got more driveshaft segments and carrier bearings than you can shake a stick at.

This is also why longer vehicles generally end-up with longer transmission housings/tailshafts--to shorten the driveshaft length to something manageable. Cadillac TH400 transmissions had the longest tailshafts of all, full-size cars got the next-longest, and compact/intermediate cars got the short tailshafts.

Although the stresses are different, the things that make a good driveshaft also make a good pushrod--material, wall-thickness, diameter, length, etc.

Good points made! That must be why the half ton Burbs have that BIG driveshaft, but it's not a two piece.

 

[Pinger]

Good points made! That must be why the half ton Burbs have that BIG driveshaft, but it's not a two piece.

My 3/4 ton Burb has the same shaft.
What Schurkey refers to is 'second moment of area' where stiffness is maximised by increasing diameter and allows aluminium an advantage over steel.
Although aluminium is around one third the weight of steel it is also only one third as strong so three times more is used than when steel is to obtain the same strength. For tubes though, when maximising the diameter, the steel has to be used so sparingly its wall thickness isn't enough to support anything or be easily joined. Aluminium at the same diameter as steel can have three times the wall thickness so in service is more usable. Or, to look at from the other direction, for the same wall thickness it can be three times the diameter which plays to second moment of area where the distribution of the material as far from the central axis increases bending stiffness - which stops pushrods bending and propshafts getting out of line and self-destructing.

 

[someotherguy]

Good points made! That must be why the half ton Burbs have that BIG driveshaft, but it's not a two piece.

Also aluminum vs. steel. All the ones I've seen on GMT400 Suburbans, anyway.

Richard

 

[Erik the Awful]

The whole truck is almost 22 feet with the brush guard on the front and the trailer ball mount in back.

My Cadillac was 21' long. It had a one-piece driveshaft that was 6' long and about 6" in diameter with double-cardan joints at each end.

Funny thing, my '06 Mustang came with a two-piece steel driveshaft with a carrier bearing. The whole assembly was about 60 lbs. When the u-joints started making noise I replaced it with a Ford Racing one-piece aluminum driveshaft that weighed less than 20 lbs.

 

[Road Trip]

Actually the 3/4 ton with a big block had one too; we just didn't drive it long enough to have issues with the carrier bearing assembly.

I would figure all 3500s would have one, just because of the weight loads they're designed for. Especially on big block and diesel engine equipped trucks.

Same here. My big block '99 C2500 (RCLB 131.5" wheelbase) has a 2-pc steel
driveshaft with a carrier bearing. Good discussion, I was just admiring it, and
now I'm going to take it to the next level & actually put a grease gun to it! :0)

 

[HotWheelsBurban]

My Cadillac was 21' long. It had a one-piece driveshaft that was 6' long and about 6" in diameter with double-cardan joints at each end.

Funny thing, my '06 Mustang came with a two-piece steel driveshaft with a carrier bearing. The whole assembly was about 60 lbs. When the u-joints started making noise I replaced it with a Ford Racing one-piece aluminum driveshaft that weighed less than 20 lbs.

Yup Cadillac used those double Cardan u joints for a long time. The '74 that donated its running gear to the '75 GMC Burb we had, had those. I think the driveshaft weighs 150 lbs....

 

[someotherguy]

Yup Cadillac used those double Cardan u joints for a long time. The '74 that donated its running gear to the '75 GMC Burb we had, had those. I think the driveshaft weighs 150 lbs....

Back in the late 80's I had a girlfriend with a mid 70's Caddy hearse. The double cardan joints were going bad on it and I thought hey; I've done plenty of u-joints already, I bet I can do these, too.

Nope. Wrong. I mean, I probably could've done it, if I persisted, but it seemed unwise at the time.

Ended up taking that whole assembly to the driveshaft shop, let the pros do it..

Richard