Why a 2 piece driveshaft?

[gearys 5600]

I have a one piece shaft in my static dropped yellow 69, No problems, I had a local driveshaft shop build mine.

[pritch]

I thought about converting to a one-piece, but then I decided, why re-invent the wheel? It seems to me if I had to get a larger diameter, I would maybe run into clearance issues where it passes through the member that the trailing arms are connected to.

But I've always had one nagging question about two (or more) piece shafts. Does the carrier bearing(s) ever interfere with the movement of the yoke in the transmission? It looks to me like the carrier bearing is solid, I mean, not intended to have any give, so as the rear end travels up and down, forcing front and back movement onto the driveshaft, does it bind up at the carrier bearing?

[WIDESIDE72]

Originally Posted by pritch

I thought about converting to a one-piece, but then I decided, why re-invent the wheel? It seems to me if I had to get a larger diameter, I would maybe run into clearance issues where it passes through the member that the trailing arms are connected to.

But I've always had one nagging question about two (or more) piece shafts. Does the carrier bearing(s) ever interfere with the movement of the yoke in the transmission? It looks to me like the carrier bearing is solid, I mean, not intended to have any give, so as the rear end travels up and down, forcing front and back movement onto the driveshaft, does it bind up at the carrier bearing?

I have not looked at a 2 pc shaft in a while, but isnt the splined part of the front section that goes into the carrier bearing supposed to slide in and out with rear axle movement?

[70blackfish]

my 70 chevy swb had a 2 piece with a stock 350 and turbo 400 trans.

it would shift hard, I replaced that center support all the time. (hated it!)

my 69 gmc swb 6 cyl. has a 1 piece...

[Shyguy]

Here is another reason for a two piece drive shaft, if you have a SM-420 or SM-465 transmission they do not have a slip joint so the two piece is necessary to take up for the movement of the driveshaft when the suspension flexes.

Just another bit of info.

[long67]

Not all carrier bearings are splined. Mine is solid. the bearing is pressed on the drive shaft behind the yoke that connects the two shafts. really does not allow for much movement.

[69GWC]

Originally Posted by Shyguy

Here is another reason for a two piece drive shaft, if you have a SM-420 or SM-465 transmission they do not have a slip joint so the two piece is necessary to take up for the movement of the driveshaft when the suspension flexes.

Just another bit of info.

My 69 has a sm-465 wi5h a one piece shaft, but its a 4wd and the shaft has a built in slip joint.. . Just thought I would throw that info out there..
Posted via Mobile Device

[midniteblues]

I've never owned a lwb truck(except s10 and parts trucks) but I had swb's with both shafts and never understood why they came both ways either

[brad_man_72]

Originally Posted by long67

Not all carrier bearings are splined. Mine is solid. the bearing is pressed on the drive shaft behind the yoke that connects the two shafts. really does not allow for much movement.

I build driveshafts for a living.

The carrier bearing you are talking about allows for plenty of movement, trailing arm trucks Don't need much slip as the rear end doesn't move straight up and down, it swings in an arc very simmilar to the driveshaft.

I build one piece driveshafts for swb and lwb trucks like ours pretty frequently and have never had an issue. I would never attempt modifying a shaft at home especially the way the guys on hot rod tv did it.

Remember to have your driveshafts ballanced guys and gals. Its a lot cheaper than a new trans tailhousing.
Posted via Mobile Device

[ERASER5]

My '71 Chevy has the tear "drop" type of carrier like most people talk about.

My '70 GMC has a differnent carrier. The bearing is just a standard bearing like you could get at any bearing supply house. there is a rubber doughnut that goes over the bearing. There are 2 large clam shells the encase the bearing/doughnut. This thing is stout. I should get some pictures of it as I have never seen another one, but surely there are out there.

[67chevemall]

67 stepside with stock one piece shaft. 6cly 3 on the tree....

[pritch]

Originally Posted by brad_man_72

I build driveshafts for a living.

The carrier bearing you are talking about allows for plenty of movement, trailing arm trucks Don't need much slip as the rear end doesn't move straight up and down, it swings in an arc very simmilar to the driveshaft.

I build one piece driveshafts for swb and lwb trucks like ours pretty frequently and have never had an issue. I would never attempt modifying a shaft at home especially the way the guys on hot rod tv did it.

Remember to have your driveshafts ballanced guys and gals. Its a lot cheaper than a new trans tailhousing.
Posted via Mobile Device

That certainly makes sense.

[brad_man_72]

Originally Posted by ERASER5

My '71 Chevy has the tear "drop" type of carrier like most people talk about.

My '70 GMC has a differnent carrier. The bearing is just a standard bearing like you could get at any bearing supply house. there is a rubber doughnut that goes over the bearing. There are 2 large clam shells the encase the bearing/doughnut. This thing is stout. I should get some pictures of it as I have never seen another one, but surely there are out there.

Those are pretty uncommon, may have been a 3/4+ ton thing or a leaf spring truck thing. I know I've only seen a half dozen or so in the last 5 years.

A lot of prople think the car style or teardrop style carrier bearings are weak. Carrier bearings don't just fail, our 2 piece driveshafts can very easily be reassembled incorrectly, changing the timing of the bolt on yoke or putting the rear shaft in 180* out or even backwards will cause a vibration. Many people just think old trucks are supposed to have some vibrations and are completely unaware of why ther carrier bearing fails 3 times a year, some even go out and buy one of those fancy billet/poly supports instead of fixing the real problem, an out of phase and or ballance issue.
Posted via Mobile Device

[long67]

Originally Posted by brad_man_72
I build driveshafts for a living.

The carrier bearing you are talking about allows for plenty of movement, trailing arm trucks Don't need much slip as the rear end doesn't move straight up and down, it swings in an arc very simmilar to the driveshaft.

I build one piece driveshafts for swb and lwb trucks like ours pretty frequently and have never had an issue. I would never attempt modifying a shaft at home especially the way the guys on hot rod tv did it.

Remember to have your driveshafts ballanced guys and gals. Its a lot cheaper than a new trans tailhousing.
Posted via Mobile Device

That makes sense, I have replaced it twice, last time because the housing broke. First time because of bearing.

[ERASER5]

Brad man, The '70 is a GMC, so it has leaf springs, but is still a 1/2 ton. As for the"weak" factory tear drop carrier, I believe you are right on the money. Those things servived 30 years, then suddenly they are weak junk. I doubt it. Other factors are more likely involved, just like you mentioned.

I like to draw/scribe a line so I can match the orientaion back up. But that's just me.

[Builtbychevy]

Originally Posted by brad_man_72

I build driveshafts for a living.

The carrier bearing you are talking about allows for plenty of movement, trailing arm trucks Don't need much slip as the rear end doesn't move straight up and down, it swings in an arc very simmilar to the driveshaft.

I build one piece driveshafts for swb and lwb trucks like ours pretty frequently and have never had an issue. I would never attempt modifying a shaft at home especially the way the guys on hot rod tv did it.

Remember to have your driveshafts ballanced guys and gals. Its a lot cheaper than a new trans tailhousing.
Posted via Mobile Device

I have a stock height '71 LWB. I was looking to go to the 1 piece without modifying the crossmember and without lowering the truck. Do you recall any modifications or diameter etc?

[hardwaycooke]

Contemplated trying to get a 1 piece made for my 500hp longbed. After much discussion with reputable drive shaft shops and a couple my buddies who build high end pro stock engines for a living , I decided to keep my 2 piece, get it balanced, get new heavy duty u-joints and a new improved yoke to handle my needs. I love it. It does not wobble, rattle, shake, etc...oh, and a new carrier. Much cheaper than having one built ad probably much smarter.

[brad_man_72]

Originally Posted by Builtbychevy

I have a stock height '71 LWB. I was looking to go to the 1 piece without modifying the crossmember and without lowering the truck. Do you recall any modifications or diameter etc?

3.5" diameter tubing will fit through the crossmember. Id worry about the shaft hitting the bottom of the crossmember at stock ride height.

[Mike_The_Grad]

Originally Posted by brad_man_72

3.5" diameter tubing will fit through the crossmember. Id worry about the shaft hitting the bottom of the crossmember at stock ride height.

I've been searching the forums for a lil over an hour,and I still have not found an answer to what I believe is a relatively easy scenario....how do I reengage the driveshaft to transmission once the engine and transmission have been reinstalled in the vehicle,without removing the entire assembly? I know this may not be the correct thread but direction is welcomed.. Thanks in advance.

[brad_man_72]

Originally Posted by Mike_The_Grad

I've been searching the forums for a lil over an hour,and I still have not found an answer to what I believe is a relatively easy scenario....how do I reengage the driveshaft to transmission once the engine and transmission have been reinstalled in the vehicle,without removing the entire assembly? I know this may not be the correct thread but direction is welcomed.. Thanks in advance.

Put the driveshaft in trans yoke first, then pinion yoke. If its a 2 piece then you set truck to ride height then tighten bolts on center support bearing.

[2009kvfd976]

i have a 68 lwb with a 350/th700. engine is bone stock crate goodwrench but will get vortec heads, xe268 or thumpr cam, headers, performer intake and 600 carb. trans will be swapped for a 700r4 and rear gears will have 3.42 and eaton tru trac locker. will i be able to have a 1pc drive shaft made? or a 1pc shaft from like a 90 gmc 2wd lwb? it currently has a 2 pc shaft...

[mike16]

engineers do things for a reason. may be they study the tea leaves or cat guts on the highway. long drive shafts can get whippy at speed. also remember that drive shaft angle can change based on loads. I dont know but i'm betty on the cat gut theory

[Mike_The_Grad]

Originally Posted by mike16

engineers do things for a reason. may be they study the tea leaves or cat guts on the highway. long drive shafts can get whippy at speed. also remember that drive shaft angle can change based on loads. I dont know but i'm betty on the cat gut theory

I had forgotten I was subbed to this thread, how strange I was notified of an update to this thread at the same time I'm facing a 2 piece driveshaft dilemma on my '72 custom/10 LWB with factory overload rear leaf suspension. I had removed the driveshaft a couple years ago to rebuild the 350 sbc, I had to remove the actual center bearing support bracket from the frame in order to remove the driveshaft. Now I can't remember which of the two 4-bolt bracket mounting locations (heightwise) is the correct one for my vehicle. I do have the factory assembly manual and it does not define which of the two is correct. It does differentiate between the two based on RPO#'s but only for 1968 vehicles, with no mention anywhere else in the entire book of any other production years.
Picture for reference and clarification on which holes I'm referring to.

[mike16]

Originally Posted by Mike_The_Grad

I had forgotten I was subbed to this thread, how strange I was notified of an update to this thread at the same time I'm facing a 2 piece driveshaft dilemma on my '72 custom/10 LWB with factory overload rear leaf suspension. I had removed the driveshaft a couple years ago to rebuild the 350 sbc, I had to remove the actual center bearing support bracket from the frame in order to remove the driveshaft. Now I can't remember which of the two 4-bolt bracket mounting locations (heightwise) is the correct one for my vehicle. I do have the factory assembly manual and it does not define which of the two is correct. It does differentiate between the two based on RPO#'s but only for 1968 vehicles, with no mention anywhere else in the entire book of any other production years.
Picture for reference and clarification on which holes I'm referring to.

all kidding aside. looking at your cross member it is covered with a lite suface rust except where the carrier bearing mounting brackets attach. the carrier bearing mounting brackets covered and protected the paint under the mounting brakets. That would be a clue as to where the brackets origonally mounted. Hpe that helps.

[Mike_The_Grad]

Originally Posted by mike16

all kidding aside. looking at your cross member it is covered with a lite suface rust except where the carrier bearing mounting brackets attach. the carrier bearing mounting brackets covered and protected the paint under the mounting brakets. That would be a clue as to where the brackets origonally mounted. Hpe that helps.

I agree. I had tried both mounting locations at one time with no noticeable difference. I think the difference comes into play as the suspension travels. I just don't want to pick the wrong one and have the rear of the transmission beat up or have my pinion bearing take a beating either. Does anyone know how to determine which location is correct?