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Discussion Starter #1
Hey guys im new to the forum. I have a 2wd 91 s10 4.3 that i put a th400 in. Im having a problem figuring out the driveshaft. I cant afford to have one made. By any chance has anyone here done this swap in the same truck? If so do you know how long the driveshaft was? Are there any cheaper options then having one made?
 

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You probably won't want to hear this, but Turbo 400's bring a pretty penny in the hotrod crowd. You might consider selling it and getting a 700R4. Your engine and wallet will thank you.

BTW...Moved to Transmission/Rearend
 

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Since you already have the TH400 in the truck, why not just get a front ujoint yoke for it and measure the length you need. I'm sure with enough JY shopping you'll find one the right length.
You original trans was 30-3/4" OAL. The TH400 came in 3 lengths. Depending on whether you have the 4", 9'', or 13" tail housing. Resulting in OAL lengths of either 28-3/8", 33-7/8", or 37-7/8".
So depending on which you have you can do the math to figure out how much shorter or in the case of the short TH400 how much longer you need.
This is making the assumption that you didn't move the 4.3's location.
You are also going to have to use a hybrid U-joint on one end of the driveshaft you find since the TH400 front yoke uses a larger u-joint than the S10 uses. They're available, just not as common.

Why did you put a TH400 behind a 4.3? You're losing OD and creating problems that aren't helping anything. Granted the TH400 won't break behind a 4.3, but it's overkill. I've been working on cars and trucks for close to 60 years and S10's for 35 years and I can't think of any reason to do it. Poorer performance, worse gas mileage, more engine wear.
Lose, lose, lose scenario.
But it's you truck and if you need more info to do your thing, just ask.
 

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You can make your own IF you have any idea of what you are doing ! If you can't find the right length just have one made - there not that much.
 

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I just bought 2 used driveshafts off Craigslist for $5 each. Helped that I knew what length I needed and he had measured the ones for sale the same way. U-joint center to center is the most common way.
Best thing to do is stick a yoke in your trans and measure with it on the ground. TH400 yokes are bigger than what was in the truck.
Your driveshaft probably has 1310 joints, 1.062" caps. There are two different size TH400 yokes, one has 1330 joints and the other has 1350 joint. There are conversion ujoints from 1310 to 1330 and 1310 to 1350
https://www.speedwaymotors.com/1310-1330-Series-Chevy-to-Ford-U-Joint,6989.html?sku=91048316&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=CjwKCAiAh5_uBRA5EiwASW3IaqWuRj4YilCyD41cQTTQFS3bJbPsbPb3thBqIc01XONCE2W2Xvnq2BoC4OMQAvD_BwE
 

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Discussion Starter #6
Since you already have the TH400 in the truck, why not just get a front ujoint yoke for it and measure the length you need. I'm sure with enough JY shopping you'll find one the right length.
You original trans was 30-3/4" OAL. The TH400 came in 3 lengths. Depending on whether you have the 4", 9'', or 13" tail housing. Resulting in OAL lengths of either 28-3/8", 33-7/8", or 37-7/8".
So depending on which you have you can do the math to figure out how much shorter or in the case of the short TH400 how much longer you need.
This is making the assumption that you didn't move the 4.3's location.
You are also going to have to use a hybrid U-joint on one end of the driveshaft you find since the TH400 front yoke uses a larger u-joint than the S10 uses. They're available, just not as common.

Why did you put a TH400 behind a 4.3? You're losing OD and creating problems that aren't helping anything. Granted the TH400 won't break behind a 4.3, but it's overkill. I've been working on cars and trucks for close to 60 years and S10's for 35 years and I can't think of any reason to do it. Poorer performance, worse gas mileage, more engine wear.
Lose, lose, lose scenario.
But it's you truck and if you need more info to do your thing, just ask.
Yeah i know its a little overkill but in the past ive had 2 s10s and 3 tahoes which all had 700r4s with aprox 170k and they all blew up. Not even any slip or warnings just dead. Im hard on my vehicles and have a really heavy foot plus i also Live in the city. Im not stressing the 4.3 cause its one of the most reliable motors chevy made and i also know this truck was taken care of. But to answer your question eventually i plan on building a 350 and putting it in or maybe even rebuilding the 4.3 and throwing in a few bolt on's. Plus i got a good deal on a th400 with 36,000 out of a old motorhome. I found someone to replace all seals for 225 and only paid 400 for the trans. Its only gonna be driven in the city so overdrive dont matter. And how much u think it'll affect gas mileage
 

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Discussion Starter #7
My drivshaft had 3r u joints. I cant seem to figure out what size u joint and straps i need at the th400s yoke. Its a bolt on fixed yolk.
 

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Discussion Starter #8
Since you already have the TH400 in the truck, why not just get a front ujoint yoke for it and measure the length you need. I'm sure with enough JY shopping you'll find one the right length.
You original trans was 30-3/4" OAL. The TH400 came in 3 lengths. Depending on whether you have the 4", 9'', or 13" tail housing. Resulting in OAL lengths of either 28-3/8", 33-7/8", or 37-7/8".
So depending on which you have you can do the math to figure out how much shorter or in the case of the short TH400 how much longer you need.
This is making the assumption that you didn't move the 4.3's location.
You are also going to have to use a hybrid U-joint on one end of the driveshaft you find since the TH400 front yoke uses a larger u-joint than the S10 uses. They're available, just not as common.

Why did you put a TH400 behind a 4.3? You're losing OD and creating problems that aren't helping anything. Granted the TH400 won't break behind a 4.3, but it's overkill. I've been working on cars and trucks for close to 60 years and S10's for 35 years and I can't think of any reason to do it. Poorer performance, worse gas mileage, more engine wear.
Lose, lose, lose scenario.
But it's you truck and if you need more info to do your thing, just ask.
Yeah i know its a little overkill but in the past ive had 2 s10s and 3 tahoes which all had 700r4s with aprox 170k and they all blew up. Not even any slip or warnings just dead. Im hard on my vehicles and have a really heavy foot plus i also Live in the city. Im not stressing the 4.3 cause its one of the most reliable motors chevy made and i also know this truck was taken care of. But to answer your question eventually i plan on building a 350 and putting it in or maybe even rebuilding the 4.3 and throwing in a few bolt on's. Plus i got a good deal on a th400 with 36,000 out of a old motorhome. I found someone to replace all seals for 225 and only paid 400 for the trans. Its only gonna be driven in the city so overdrive dont matter. And how much u think it'll affect gas mileage
 

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How's that gonna work with fixed joints on both ends? As the axle moves up and down the driveshaft moves in and out.
I'm sure the motor home had a 2 piece shaft with a slip joint of some kind in the middle.
TH 400 normally have 1330 or 1350 u-joints. Ideally you can find a 1330 yoke. Not as much bigger than the 3R/S44.
This explains what you need to connect them once you find the right length shaft.
 

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Discussion Starter #10
How's that gonna work with fixed joints on both ends? As the axle moves up and down the driveshaft moves in and out.
I'm sure the motor home had a 2 piece shaft with a slip joint of some kind in the middle.
TH 400 normally have 1330 or 1350 u-joints. Ideally you can find a 1330 yoke. Not as much bigger than the 3R/S44.
This explains what you need to connect them once you find the right length shaft.
My truck has a 2 piece driveshaft with a slip at center bearing on the rear side. Im just gonna have a longer rear driveshaft made, put on and balanced. Shops here want close to $300 to do it. Then ill jist move the center bearing forward a little bit.
 

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From Denny's driveshafts again.
What is the difference between 1310, 1330 and 1350 Series?

The "series" of a driveshaft or universal joint is determined by the actual dimensions of the u-joint. While the front and rear u-joint can be of two different sizes the shaft is only as strong as the smaller one. The 1310 series u-joint measures approximately 3 1/4 inches wide. The 1330 and 1350 both measure approximately 3 5/8 wide. The 1310 and 1330 series can have cap diameters of 1 1/16 and/or 1 1/8 inch or a combination of both sizes. The 1350 series has a cap diameter of 1 3/16 inch and the body and journals are bigger than the 1310 or 1330. Remember 1350 is almost never found in production car driveshafts.
 
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