big block driveline???

[lyrikz]

The truck is a 71 SWB stepside. Came with a I6 in it.. Im installing my big block shortly and i need a new driveline. Now, since im useing stock BB engine mounts, cant i just purchase a drivline for a BB chevy of that same year make with a TH400 transmission????

Thanks for the info.

[Longhorn Man]

In theory yes.
However, odds are slim that you'll locate a SWB with a big block. It'd be much quicker to call your local drive shaft shop, have them tell you how they want you to measure it (make sure your ride height/weight is about right) and have them make you one.

[68350]

I would try for a one piece, too. It bypasses the hassle of the bearing going out.

[chevy72blu]

Measure from the hub coming out of the rear end to the tailshaft of your transmission and take that to your local reputable driveline shop. It shouldnt cost more than $150-$180 to have them make you a new one from scratch.

[Longhorn Man]

To add to that... make that measurement with the suspention loaded, and the yoke 1/2 way in, 1/2 way out of the tranny.
That is the driveshaft industry standard... but once in a while, you'll get some idiot that does it another way, so get the info fromt eh dude doin the work.
You could also take your measurements, and spend a day in the junk yard... but it'll probably need U joints and just isn't worth the work IMO.

[lyrikz]

Any tips for an air ride suspension.. Do i measure with it fully dropped or fully inflated?

[chevy72blu]

Originally Posted by Longhorn Man

To add to that... make that measurement with the suspention loaded, and the yoke 1/2 way in, 1/2 way out of the tranny.
That is the driveshaft industry standard... but once in a while, you'll get some idiot that does it another way, so get the info fromt eh dude doin the work.
You could also take your measurements, and spend a day in the junk yard... but it'll probably need U joints and just isn't worth the work IMO.

Longhorn covered it better than I did.

As for bags, I have never used them. But, it would make most sense to measure at ride height.

[Longhorn Man]

Talk to them. They may recomend a 2 piece shaft

[lyrikz]

Originally Posted by Longhorn Man

Talk to them. They may recomend a 2 piece shaft

LM,
You mentioned slip yoke. My truck doesnt have a slip yoke. the rear mounted to the diff is ujoint solid, and the end on my th400 is solid. No slip yoke. Is that needed???

[Hart_Rod]

Originally Posted by lyrikz

LM,
You mentioned slip yoke. My truck doesnt have a slip yoke. the rear mounted to the diff is ujoint solid, and the end on my th400 is solid. No slip yoke. Is that needed???

The piece that goes into the tranny is called the slip yoke, it will slide in and out as the rear suspension moves. As far as air ride, if you have a serious drop, you may want to go with a 2 piece because it will minimize the pinion angle change. Here's a picture of my setup for my 69 Burb.

[lyrikz]

Originally Posted by Hart_Rod

The piece that goes into the tranny is called the slip yoke, it will slide in and out as the rear suspension moves. As far as air ride, if you have a serious drop, you may want to go with a 2 piece because it will minimize the pinion angle change. Here's a picture of my setup for my 69 Burb.

So that part that is on the end of the tranny slides in and out??? I grabbed the end of that and drug the transmission by it and it didnt come out......

[Hart_Rod]

Originally Posted by lyrikz

So that part that is on the end of the tranny slides in and out??? I grabbed the end of that and drug the transmission by it and it didnt come out......

It should come out, . Take a rubber hammer and tap on it.

[lyrikz]

Originally Posted by Hart_Rod

The piece that goes into the tranny is called the slip yoke, it will slide in and out as the rear suspension moves. As far as air ride, if you have a serious drop, you may want to go with a 2 piece because it will minimize the pinion angle change. Here's a picture of my setup for my 69 Burb.

So, if im measuring for the new driveline i want to measure from these two points?

[Longhorn Man]

That tranny is set up for a 2 piece shaft. There is a slip in the center of the shaft.
You'll need to convert your trany to a slip yoke.

[70rs/ss]

Nope, on the 400 the toke bolts to the tailshaft on some and a slip on the others. Get a DS from a newr model truck and have it cut down to fit your truck. You can take the bolt on yoke out and install a slip yoke (you'll need to do this if you want a one piece shaft) or stick with the bolt on and get a two piece shaft with the slip in the center of the shaft. I don't do air bags, but I'd guess a mesurement fully air up and air out would let the driveshaft shop figure out if a one or 2 piece shaft is needed as well as the length.

[lyrikz]

Originally Posted by 70rs/ss

Nope, on the 400 the toke bolts to the tailshaft on some and a slip on the others. Get a DS from a newr model truck and have it cut down to fit your truck. You can take the bolt on yoke out and install a slip yoke (you'll need to do this if you want a one piece shaft) or stick with the bolt on and get a two piece shaft with the slip in the center of the shaft. I don't do air bags, but I'd guess a mesurement fully air up and air out would let the driveshaft shop figure out if a one or 2 piece shaft is needed as well as the length.

sweet golden 4lb 8oz baby jessus, the plot thickens....

[70rs/ss]

Yeah, sorry the th400 was used as a heavy truck trans, so it can be bolt on yoke or slip if it was a car trans or the like. Call a Driveshaft shop and tell them what you are doing, they will tell you where to measure from (I have been told 2 or 3 different places by different shops, so I think it is a matter of each guy's preference) The used shaft will help in that cutting one down is way cheaper than building one. The late model trucks have beefy driveshafts. Hope this helping and not confusing ya!?

[lyrikz]

Originally Posted by 70rs/ss

Yeah, sorry the th400 was used as a heavy truck trans, so it can be bolt on yoke or slip if it was a car trans or the like. Call a Driveshaft shop and tell them what you are doing, they will tell you where to measure from (I have been told 2 or 3 different places by different shops, so I think it is a matter of each guy's preference) The used shaft will help in that cutting one down is way cheaper than building one. The late model trucks have beefy driveshafts. Hope this helping and not confusing ya!?

Well, i also have the setup off the donor truck. Thats a two piece driveline setup... It was a LWB truck, but im sure that wouldnt be hard having them cut that down.... I will call my driveline shop.

[70rs/ss]

Yep, they can cut it down to fit if you want/need a 2-piece, but I was suggesting a late model one piece for the donor to be shortened into a 1-piece. The yoke thing is funky on the 400 as it came both ways, but usually as a bolt in on a truck cause the mostly came with a 2-piece when a 4oo was used (heavy duty, usually means longbed).

[lyrikz]

Originally Posted by 70rs/ss

Yep, they can cut it down to fit if you want/need a 2-piece, but I was suggesting a late model one piece for the donor to be shortened into a 1-piece. The yoke thing is funky on the 400 as it came both ways, but usually as a bolt in on a truck cause the mostly came with a 2-piece when a 4oo was used (heavy duty, usually means longbed).

So regardless if i go with 1 or two piece, i need some kind of slip yoke....

[70rs/ss]

Yes, as the rear end moves up and down in suspension travel the DS has to get longer and shorter. If a one piece, the slip yoke will be in the trans, on a 2 piece there will be a slip shaft in between the two piece of DS. Make sense? Sorry if I am confusing ya, picts would be easier but I dont have any?

[lyrikz]

Originally Posted by 70rs/ss

Yes, as the rear end moves up and down in suspension travel the DS has to get longer and shorter. If a one piece, the slip yoke will be in the trans, on a 2 piece there will be a slip shaft in between the two piece of DS. Make sense? Sorry if I am confusing ya, picts would be easier but I dont have any?

Completely understand... My 3 speed saginaw has the slip yoke on the tranny and the driveline just slides in. Then it bolts to the rear end.. Its ALLLMOOST long enough. ahaha....

[Hart_Rod]

Originally Posted by lyrikz

Completely understand... My 3 speed saginaw has the slip yoke on the tranny and the driveline just slides in. Then it bolts to the rear end.. Its ALLLMOOST long enough. ahaha....

Check this out.

http://www.iedls.com/twopiece.html

I think it even tells you how to measure them.....

[70rs/ss]

That looks like the ticket. I am not into 2-piece shafts, but a good aftermarket one would be the ticket behind a BBC with bags.

[Longhorn Man]

that's what all the 2 piece shafts I've had look like (except the high dollar C-bearing there)
Slip yoke up front, and a slip shaft in the middle too.
My 70 3/4 ton longhorn (350/TH350)
My 70 one ton Longhorn (350/TH nfc)
My 3/4 ton burb (402/TH400)
The 1/2 ton parts burb I left in Washington (402/TH400)
The 72 3/4 ton Longhorn I had for parts (307/TH350)