one or 2 piece driveline for a 700R4 swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Ricks1971** · 07-24-2021, 05:48 PM

I am putting a 700R4 trans in my 67 C10 longbed and was hoping for help in putting a one piece driveline in the truck thanks Rick

blackdiesel · 07-24-2021, 09:23 PM

Rule of thumb is 69" max center of u joint to center of u joint. If it's longer than that you'll need a carrier bearing.

Accelo · 07-24-2021, 09:52 PM

The issue is the drive-line's diameter.

As they get longer they need to get bigger in diameter to avoid whip. Exactly why the front drivelines on four wheels drives are smallish in diameter, they are short.
When you go for a long drive shaft, of the correct diameter to avoid whip, it increases the chance it will impact the cross member because of the increased diameter.
An overdrive transmission exacerbates the whipping issue as the driveline speed goes up by the o/d ratio. On the plus side the 700R4 transmission is 3-3/8 longer than a short shaft 350. So this helps shorten the driveline extra length required for a one piece drive shaft.

GM knew what they were doing, for the most part. I recommend staying with the two piece driveline, on a long box truck, for this reason. Especially if the truck is taken on bumpy roads or has an overdrive transmission.
Short box trucks avoid one piece driveline issues, for the most part. Lowering the truck tends to help center the driveline in the top portion of the cross member and lowering shocks avoid over extension of the differential.
Rick

Davidf · 07-25-2021, 09:21 AM

I installed a one piece in long bed with LS and 4L60E. The driveshaft length needed was exactly 69” and 3.5” diameter tube. It is close the bottom of the cross ember, but works. My truck is not lowered. The LS utilizes Hooker Blackheart engine stands and crossmember.

I made the switch because I got tired of constantly replacing the center bearing on the two piece. The rubber would go after about one year resulting in driveline vibration on decel and strong acceleration.

Sparky dave · 07-26-2021, 05:15 PM

My 69 longbed has 700r4 and one piece drive shaft. Is pretty chunky maybe 4 inch wide. Don't know much more was like that when I bought it. Drives nice though

**MySons68C20** · 07-26-2021, 08:36 PM

Did this on the 68 super happy with it!

07-24-2021, 05:48 PM	#1
Ricks1971 Senior Member Join Date: Mar 2006 Location: Clarkrange Tennessee Posts: 1,757	one or 2 piece driveline for a 700R4 swap I am putting a 700R4 trans in my 67 C10 longbed and was hoping for help in putting a one piece driveline in the truck thanks Rick

07-24-2021, 09:23 PM	#2
blackdiesel Registered User Join Date: Jan 2009 Location: Omaha, Arkansas Posts: 929	Re: one or 2 piece driveline for a 700R4 swap Rule of thumb is 69" max center of u joint to center of u joint. If it's longer than that you'll need a carrier bearing. __________________ '57 Chevy Pickup '56 GMC LCF Cummins '38 Chrysler Royal '57 2wd change http://67-72chevytrucks.com/vboard/s...light=speedway

07-24-2021, 09:52 PM	#3
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,159	Re: one or 2 piece driveline for a 700R4 swap The issue is the drive-line's diameter. As they get longer they need to get bigger in diameter to avoid whip. Exactly why the front drivelines on four wheels drives are smallish in diameter, they are short. When you go for a long drive shaft, of the correct diameter to avoid whip, it increases the chance it will impact the cross member because of the increased diameter. An overdrive transmission exacerbates the whipping issue as the driveline speed goes up by the o/d ratio. On the plus side the 700R4 transmission is 3-3/8 longer than a short shaft 350. So this helps shorten the driveline extra length required for a one piece drive shaft. GM knew what they were doing, for the most part. I recommend staying with the two piece driveline, on a long box truck, for this reason. Especially if the truck is taken on bumpy roads or has an overdrive transmission. Short box trucks avoid one piece driveline issues, for the most part. Lowering the truck tends to help center the driveline in the top portion of the cross member and lowering shocks avoid over extension of the differential. Rick Last edited by Accelo; 07-24-2021 at 10:08 PM.

07-25-2021, 09:21 AM	#4
Davidf Registered User Join Date: Nov 2014 Location: Austin Posts: 749	Re: one or 2 piece driveline for a 700R4 swap I installed a one piece in long bed with LS and 4L60E. The driveshaft length needed was exactly 69” and 3.5” diameter tube. It is close the bottom of the cross ember, but works. My truck is not lowered. The LS utilizes Hooker Blackheart engine stands and crossmember. I made the switch because I got tired of constantly replacing the center bearing on the two piece. The rubber would go after about one year resulting in driveline vibration on decel and strong acceleration.

07-26-2021, 05:15 PM	#5
Sparky dave Registered User Join Date: Nov 2017 Location: Leeds west yorkshire Posts: 307	Re: one or 2 piece driveline for a 700R4 swap My 69 longbed has 700r4 and one piece drive shaft. Is pretty chunky maybe 4 inch wide. Don't know much more was like that when I bought it. Drives nice though __________________ 69 longbed 350 700r4 3.73 POSI cruiser

07-26-2021, 08:36 PM	#6
MySons68C20 Senior Member Join Date: Sep 2014 Location: Wenatchee, Wa Posts: 897	Re: one or 2 piece driveline for a 700R4 swap Did this on the 68 super happy with it!



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