86 c/10 th400 driveshaft question

[jgage]

I have an 86 C/10 shortbed that was originally a 6 cylinder/manual trans truck that had a 350/th400 swapped in by the previous owner right before I bought it. They also attempted to change the bolt on yoke to a slip yoke, when the yoke hit the o ring lip on the output shaft they ground the yoke shirt instead of using one that was counterbored. Of course that caused a nasty vibration. I replaced the seal and the bushing in the back of the tail shaft housing and I know I need the counterbored yoke, my question is about the driveshaft. Even with the correct yoke this driveshaft is probably going to be an inch or two shorter than it should be. Does anybody know what the driveshaft length is on this setup should be? And is there a vehicle that came with a driveshaft that works for this, something I can source from a junkyard or marketplace? Or will this have to be a custom length shaft? I used my budget buying the truck and replacing the dry rotted tires, now I either need to budget source a driveshaft or let it sit for a while and squirrel away a little money at a time, otherwise the wife is gonna kick my ass, lol.

 

[Frankenchevy]

Short bed or long bed? There are probably quite a few c20s you could source a drive shaft from.

 

[jgage]

Short bed or long bed? There are probably quite a few c20s you could source a drive shaft from.

oh my bad, yeah it’s a short bed

 

[HotRodPC]

So what Turbo 400 does it have in it? Is it the short tailshaft with the bolt on yoke or is it the long tailshaft with the slip yoke?

 

[HotRodPC]

Short bed or long bed? There are probably quite a few c20s you could source a drive shaft from.

The problem there is going to be all the C20's were long beds and used a 2pc driveshaft to the bolt on yoke with the center of the 2 pieces drive shaft being where the slip is located. Being a shortbed he most likely is going to need a 1 pc driveshaft with a slip yoke.

 

[jgage]

It’s the short shaft bolt on style yoke transmission. And yes it’s the one piece driveshaft I’m looking for. Custom length might be the only option, but there’s enough of the swaps for multiple companies to offer the slip yoke with the counter birentimclear the o ring lip that I wondered if there was a known length and maybe anvehicle that came with a one piece drive that would work. Maybe not. Figured I’d ask.

 

[Frankenchevy]

The problem there is going to be all the C20's were long beds and used a 2pc driveshaft to the bolt on yoke with the center of the 2 pieces drive shaft being where the slip is located. Being a shortbed he most likely is going to need a 1 pc driveshaft with a slip yoke.

Oh, right. What is it Keith was saying about 1 vs 2 piece shafts? Had to do with axle gearing... some lwb 2wd would get a 1 piece.

 

[jgage]

I need the counterbore yoke either way, my hope was that there was a full size car or something that had a driveshaft length that worked and that someone in here knew it. Probably a long shot.

second question, is there any real advantage to the single piece driveshaft and slip yoke? How hard or costly is it to find the 2 piece shaft and bolt on yoke? I’m trying to do it on a budget, my “spend money on the c/10” fund is dry. The 350 is nine stock and likely will be for a long time. The counterbore yoke is around 100 and the driveshaft shop said at least 200 to lengthen the driveshaft I have now. Can I find a bolt on yoke and 2 piece driveshaft that will be the right length for less than that?

 

[bucket]

When I swapped my C10 from a long tail th350 to a short tail th400, it was very easy. I wanted to convert from the bolt-on yoke to a slip yoke, and my original drive shaft was a couple inches too short as well. I don't remember exactly how short it was, but I may have posted it in my build thread.

All I did was install an NP208 slip yoke from a 1/2 ton truck. It was 32 spline, longer than the original 27 spline yoke and used the same u-joint. It fit in the transmission and didn't seem to bottom out. Well, it did, but I assumed it was because the length of the yoke. It doesn't bottom out when installed and the truck has no vibrations or leaks. I don't know if it's actually "right", but it works, it was simple and it was cheap.

 

[Paladin]

I have a couple of 2 piece driveshafts I have saved from a couple of parts trucks listed in the For Sale area of the forum. Don't know exactly what you need but I can get exact measurements on them for you if needed. 1 came from a 1985 Chevy C30 2wd crewcab, the other from a 1984 GMC 3500 cab and chassis. They are both different lengths. Both for bolt on yoke.

 

[HotRodPC]

Oh, right. What is it Keith was saying about 1 vs 2 piece shafts? Had to do with axle gearing... some lwb 2wd would get a 1 piece.

They got the 1 piece if they had long shaft transmissions. This is why the C10's with Th350's use the 9 inch output shaft instead of the passenger car 6 inch. I do believe what it has more to do with is the length of the driveshaft overall. If it's to long then it get's split and slip goes in the middle, so that means the Yoke on the transmission has to be a bolt on fixed yoke that doesn't allow slip.

Now since this is shortbed truck and a bolt on short output shaft. It seems to me he could change the output shaft housing to the slip yoke type and then use a single driveshaft with a yoke on it that can slip in and out of the transmission. If you don't have the right set up then it will leak trans fluid constantly. In short, the tailshaft housing has to be the correct housing for the type of yoke used whether it be a slip yoke or a bolt on fixed yoke coming out of the transmission. The other option is to keep the fixed yoke at the transmission and have a driveshaft made where the slip is at the back at the rear end pinion yoke. This is how the 4x4 trucks are done that have the NP205 Transfer case with a fixed yoke. 1pc driveshaft and the slip is built into the driveshaft at the pinion yoke and that's where the shaft slips rather than the middle for a 2pc with a carrier bearing, or slip into the transmission.

 

[jgage]

They got the 1 piece if they had long shaft transmissions. This is why the C10's with Th350's use the 9 inch output shaft instead of the passenger car 6 inch. I do believe what it has more to do with is the length of the driveshaft overall. If it's to long then it get's split and slip goes in the middle, so that means the Yoke on the transmission has to be a bolt on fixed yoke that doesn't allow slip.

Now since this is shortbed truck and a bolt on short output shaft. It seems to me he could change the output shaft housing to the slip yoke type and then use a single driveshaft with a yoke on it that can slip in and out of the transmission. If you don't have the right set up then it will leak trans fluid constantly. In short, the tailshaft housing has to be the correct housing for the type of yoke used whether it be a slip yoke or a bolt on fixed yoke coming out of the transmission. The other option is to keep the fixed yoke at the transmission and have a driveshaft made where the slip is at the back at the rear end pinion yoke. This is how the 4x4 trucks are done that have the NP205 Transfer case with a fixed yoke. 1pc driveshaft and the slip is built into the driveshaft at the pinion yoke and that's where the shaft slips rather than the middle for a 2pc with a carrier bearing, or slip into the transmission.

I have 2 issues with my current set up, the first being you can convert the fixed yoke to a slip yoke with a yoke that has a counterbore inside it to clear the metal lip that the o ring sits against, on a fixed yoke transmission this is much closer to the rear of the output chart than it is on the fixed yoke. So the guy that did the swap used a regular yoke, which made it jam against that lip. Their solution was to grind the yoke shorter which made it not but that lip but meant that it only engages about half of the bushing in the tail shaft of the trans. Made a nasty vibration. Also wore a fro over in the yoke and wore out the bushing. But I can’t just replace the yoke with the counterbore yoke because I think the shaft is a little too short anyway.
It’s sounding like the counterbore yoke and having my shaft lengthened is about my best bet.

 

[jgage]

This is the type of yoke for anyone interested. It has a counterbore to allow it to slide over the o ring lip

https://www.dennysdriveshaft.com/p3...rged_chromoly_1350_series_32_splines_fit.html