big block driveline??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lyrikz · 05-22-2008, 09:13 PM

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 · 05-23-2008, 04:04 AM

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** · 05-23-2008, 06:11 AM

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

chevy72blu · 05-23-2008, 06:13 AM

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 · 05-23-2008, 06:18 AM

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 · 05-23-2008, 07:05 AM

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

chevy72blu · 05-23-2008, 07:52 AM

Quote:

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 · 05-23-2008, 12:27 PM

Talk to them. They may recomend a 2 piece shaft

lyrikz · 07-29-2008, 05:00 PM

Quote:

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???

Longhorn Man · 07-29-2008, 05:09 PM

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.

**Hart_Rod** · 07-29-2008, 05:15 PM

Quote:

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 · 07-29-2008, 05:27 PM

Quote:

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** · 07-29-2008, 05:35 PM

Quote:

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 · 07-29-2008, 05:41 PM

Quote:

Originally Posted by Hart_Rod

It should come out,

. Take a rubber hammer and tap on it.

tranny was just completely rebuilt. Hmm, i will try it.

70rs/ss · 07-29-2008, 05:52 PM

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 · 07-29-2008, 05:52 PM

Quote:

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?

lyrikz · 07-29-2008, 05:53 PM

Quote:

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 · 07-29-2008, 06:18 PM

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 · 07-29-2008, 06:20 PM

Quote:

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 · 07-29-2008, 06:26 PM

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 · 07-29-2008, 06:35 PM

Quote:

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 · 07-29-2008, 08:01 PM

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 · 07-29-2008, 08:13 PM

Quote:

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** · 07-29-2008, 08:49 PM

Quote:

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 · 07-29-2008, 08:51 PM

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.

05-22-2008, 09:13 PM	#1
lyrikz PITbut Join Date: Sep 2007 Location: monroe washington Posts: 3,045	big block driveline??? 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.

05-23-2008, 04:04 AM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: big block driveline??? 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.

05-23-2008, 06:11 AM	#3
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Re: big block driveline??? I would try for a one piece, too. It bypasses the hassle of the bearing going out. __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

05-23-2008, 06:13 AM	#4
chevy72blu Registered User Join Date: Apr 2004 Location: Las Vegas, NV Posts: 2,188	Re: big block driveline??? 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. __________________ RIP EastSideLowLife '72 C20 SWB convert. 5 lug, LS1/4l60e

05-23-2008, 06:18 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: big block driveline??? 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.

05-23-2008, 07:05 AM	#6
lyrikz PITbut Join Date: Sep 2007 Location: monroe washington Posts: 3,045	Re: big block driveline??? Any tips for an air ride suspension.. Do i measure with it fully dropped or fully inflated?

05-23-2008, 12:27 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: big block driveline??? Talk to them. They may recomend a 2 piece shaft

07-29-2008, 05:09 PM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: big block driveline??? 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.

07-29-2008, 05:52 PM	#15
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: big block driveline??? 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.

07-29-2008, 06:18 PM	#18
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: big block driveline??? 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!?

07-29-2008, 06:26 PM	#20
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: big block driveline??? 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).

07-29-2008, 08:01 PM	#22
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: big block driveline??? 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?

07-29-2008, 08:51 PM	#25
70rs/ss Registered User Join Date: Dec 2004 Location: Northern AZ Posts: 7,271	Re: big block driveline??? 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.



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