TH350 driveshaft options - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Ol' Red · 12-17-2015, 11:42 PM

I have an 85 half ton with a Th350. The old stock trans has the long tail shaft. The one that is going in has a lot of upgrades but it has the short tail shaft. Being that it is a long bed, stock is the long tail shaft. I don't want to take both transmissions apart to build an upgraded th350 with a long shaft. I need 72" driveshaft. Currently mine is 69". A local shop said the only way I can keep a one piece driveshaft that long is to go aluminum. That's fine but it's costly. Am I able to get away with putting a yoke on my stock driveshaft that is a few inches longer or do I need to go with getting a new shaft made? Thanks

68c10owner · 12-18-2015, 12:58 AM

You need a longer driveshaft to do it correctly. If I remember correctly the later model trucks, 88-98, had a aluminum driveshaft. You might be able to find one that works. Or just have a new front shaft made.

**MikeB** · 12-18-2015, 10:32 PM

I don't like the idea of using a longer yoke, even if you could find one. I'd bet you can find a few shops in your area that will build you a new front drive shaft for around $300. And if you take them the rear shaft, they could balance it and properly phase it to the front one.

The again, if you can run a one-piece 4-inch shaft, that's the way to go, IMO. (I didn't know you could do that on a long bed.)

jetmech85 · 12-19-2015, 12:34 AM

It has been my experience that long bed trucks use a short tail shaft 350 with a two piece drive shaft and short bed uses a long 350 one piece drive shaft. There are probably variations because I have a '91 Suburban 350 auto with a one piece shaft and sold a '91 Suburban with a two piece shaft.

barry1982 · 12-19-2015, 01:24 AM

Hmmm.... I have been down this road before. Have seen three different length TH350 driveshafts. Full size cars had a 12" tail, early 80s light duty pickups had a 9" tail (with one piece drive shaft) . Camaro/Nova's and heavy duty pickups had the 6" tail. To keep costs down you have a couple options. Go to the wrecker, and pull the shafts/steady bearing assembly from a heavy duty truck. I can't quite recall, but you also may need the support for the steady bearing. Option two is a bit "sketchy" ..... but I have successfully done it. I happen to have quite a few parts trucks, and am a fairly good welder. I cut my original shaft a few inches in from the rear u-joint with a precise tubing cutter.
Cut another driveshaft three inches longer. I butted up the new section, and clamped it tightly between two angle irons to hold it true and tack welded with my Miller Mig machine. After tacking, removed the angle irons/clamps and completed welding. Was going to take it to a machine shop for balancing, but for the heck of it tried it on the truck. Got lucky, and it worked smooth as silk.....

I ran the truck quite a few years without any issues. Like I said though, option one is better. There is probably a reason the GM Engineers called for the two piece shafts with the 6" tail trannys.

barry1982 · 12-19-2015, 01:29 AM

Hmmm.... I have been down this road before. Have seen three different length TH350 driveshafts. Full size cars had a 12" tail, early 80s light duty pickups had a 9" tail (with one piece drive shaft) . Camaro/Nova's and heavy duty pickups had the 6" tail. To keep costs down you have a couple options. Go to the wrecker, and pull the shafts/steady bearing assembly from a heavy duty truck. I can't quite recall, but you also may need the support for the steady bearing. Option two is a bit "sketchy" ..... but I have successfully done it. I happen to have quite a few parts trucks, and am a fairly good welder. I cut my original shaft a few inches in from the rear u-joint with a precise tubing cutter.
Cut another driveshaft three inches longer. I butted up the new section, and clamped it tightly between two angle irons to hold it true and tack welded with my Miller Mig machine. After tacking, removed the angle irons/clamps and completed welding. Was going to take it to a machine shop for balancing, but for the heck of it tried it on the truck. Got lucky, and it worked smooth as silk.....

I ran the truck quite a few years without any issues. Like I said though, option one is better. There is probably a reason the GM Engineers called for the two piece shafts with the 6" tail trannys.

12-17-2015, 11:42 PM	#1
Ol' Red Registered User Join Date: Feb 2013 Location: LaGrange, OH Posts: 17	TH350 driveshaft options I have an 85 half ton with a Th350. The old stock trans has the long tail shaft. The one that is going in has a lot of upgrades but it has the short tail shaft. Being that it is a long bed, stock is the long tail shaft. I don't want to take both transmissions apart to build an upgraded th350 with a long shaft. I need 72" driveshaft. Currently mine is 69". A local shop said the only way I can keep a one piece driveshaft that long is to go aluminum. That's fine but it's costly. Am I able to get away with putting a yoke on my stock driveshaft that is a few inches longer or do I need to go with getting a new shaft made? Thanks __________________ Ol' Red. 1985 GMC Sierra Classic 1500 2wd 305/th350/2:73 rear "never miss a good opportunity to shut up" "if you look back at your work and you aren't proud to you say did it then you better go back and do it over" "don't talk bad about farmers with your mouth full" Last edited by Ol' Red; 12-17-2015 at 11:51 PM.

12-18-2015, 12:58 AM	#2
68c10owner Registered User Join Date: Oct 2003 Location: Carmichael, California Posts: 3,006	Re: TH350 driveshaft options You need a longer driveshaft to do it correctly. If I remember correctly the later model trucks, 88-98, had a aluminum driveshaft. You might be able to find one that works. Or just have a new front shaft made. __________________ Anthony

12-18-2015, 10:32 PM	#3
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,544	Re: TH350 driveshaft options I don't like the idea of using a longer yoke, even if you could find one. I'd bet you can find a few shops in your area that will build you a new front drive shaft for around $300. And if you take them the rear shaft, they could balance it and properly phase it to the front one. The again, if you can run a one-piece 4-inch shaft, that's the way to go, IMO. (I didn't know you could do that on a long bed.) __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

12-19-2015, 12:34 AM	#4
jetmech85 Registered User Join Date: Sep 2014 Location: Texas Posts: 215	Re: TH350 driveshaft options It has been my experience that long bed trucks use a short tail shaft 350 with a two piece drive shaft and short bed uses a long 350 one piece drive shaft. There are probably variations because I have a '91 Suburban 350 auto with a one piece shaft and sold a '91 Suburban with a two piece shaft.

12-19-2015, 01:24 AM	#5
barry1982 Registered User Join Date: Oct 2015 Location: Waskatenau, Alberta Posts: 259	Re: TH350 driveshaft options Hmmm.... I have been down this road before. Have seen three different length TH350 driveshafts. Full size cars had a 12" tail, early 80s light duty pickups had a 9" tail (with one piece drive shaft) . Camaro/Nova's and heavy duty pickups had the 6" tail. To keep costs down you have a couple options. Go to the wrecker, and pull the shafts/steady bearing assembly from a heavy duty truck. I can't quite recall, but you also may need the support for the steady bearing. Option two is a bit "sketchy" ..... but I have successfully done it. I happen to have quite a few parts trucks, and am a fairly good welder. I cut my original shaft a few inches in from the rear u-joint with a precise tubing cutter. Cut another driveshaft three inches longer. I butted up the new section, and clamped it tightly between two angle irons to hold it true and tack welded with my Miller Mig machine. After tacking, removed the angle irons/clamps and completed welding. Was going to take it to a machine shop for balancing, but for the heck of it tried it on the truck. Got lucky, and it worked smooth as silk..... I ran the truck quite a few years without any issues. Like I said though, option one is better. There is probably a reason the GM Engineers called for the two piece shafts with the 6" tail trannys.

12-19-2015, 01:29 AM	#6
barry1982 Registered User Join Date: Oct 2015 Location: Waskatenau, Alberta Posts: 259	Re: TH350 driveshaft options Hmmm.... I have been down this road before. Have seen three different length TH350 driveshafts. Full size cars had a 12" tail, early 80s light duty pickups had a 9" tail (with one piece drive shaft) . Camaro/Nova's and heavy duty pickups had the 6" tail. To keep costs down you have a couple options. Go to the wrecker, and pull the shafts/steady bearing assembly from a heavy duty truck. I can't quite recall, but you also may need the support for the steady bearing. Option two is a bit "sketchy" ..... but I have successfully done it. I happen to have quite a few parts trucks, and am a fairly good welder. I cut my original shaft a few inches in from the rear u-joint with a precise tubing cutter. Cut another driveshaft three inches longer. I butted up the new section, and clamped it tightly between two angle irons to hold it true and tack welded with my Miller Mig machine. After tacking, removed the angle irons/clamps and completed welding. Was going to take it to a machine shop for balancing, but for the heck of it tried it on the truck. Got lucky, and it worked smooth as silk..... I ran the truck quite a few years without any issues. Like I said though, option one is better. There is probably a reason the GM Engineers called for the two piece shafts with the 6" tail trannys.



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