Transmission Options

[jorlain]

Hi Everyone,

I'm new to the forum but I'm an avid gearhead. I wanted to touch base with you guys who have a lot more experience with these trucks than I have to see if there's something I'm overlooking.

I recently picked up a 1980 C10 Stepside with the Inline 6 250 and a three on the tree. I'm weighing my options with engine\transmission swap options. Ultimately, I think I'm going to end up with a 4.8 or 5.3 swap as my power plant, although I'm still toying with the idea of a BBC. I actually kind of like the three speed, but I plan on cruising a lot in this pickup so I'm thinking I ought to convert to an OD transmission. I'm also not sure how much power the 3 speed can handle. I'll probably be in the 500 ft lbs of torque arena at the flywheel.

Finding an OD manual transmission seems to be quite the trick, though. The ones I do find are way too expensive. I'm finding NV transmissions at $1500+ and T56s at $3000+. I'm sure I could find a T5 out of a third gen camaro\firebird for cheap but I'm not sure if that would really last very long. At these prices I'd almost be better just getting a Gearvendor's overdrive unit and keeping the 3 speed. I've heard tale of a 3 speed with overdrive unit, but I've never seen one. I'm guessing they're unobtainium and parts are few and far between.

After looking at all of that, it's seriously got me considering just going to a 4l80e, as those seem to be plentiful and in the $500 arena. Add a couple hundred for a shifter, fab a crossmember, and I'd be pretty much squared away. The downside, obviously, is that it's an automatic.

What's everyone else's experience been?

Thanks!
Mike

 

[Big Chip]

Maybe look into a Nissan 350Z or 370Z manual transmission and call www.advanceadapters.com for the parts you need. I heard the owner on a podcast talking about them because the T56 is so expensive. They can tell you the HP and Torque limits of that transmission and at least give you an idea of cost.


Edit: I had one of those 3 speed with overdrive that was in a 67 GMC I had. I gave to an uncle and he put it in his 72 and drove it for years. He loved that transmission.

 

[Shorty81]

Welcome from the Buckeye State. JMO, I'd stay with the 250 3 on the tree.

 

[mcarlo86]

I have one of those 3 speed overdrive transmissions that came out of a '67 C10. It has a solenoid on it that activates the OD. Thought about swapping it into my '68 C10 in place of the SM465 that is currently in it, but haven't found a floor shifter that would work with it. I also vote for keeping the 250 and the 3 on the tree. It is getting rare to see that combo anymore as everyone seems to be doing LS swaps now days.

 

[jorlain]

I agree the 250 and 3 speed have a certain amount of cool factor, but I really would like to cruise the thing somewhat efficiently. I would really like to keep the 3 speed. I wonder if I can hunt down one of those OD units for not too much scratch.

 

[Rhett Croley]

I've got a 700r4 that my transmission guy built for me to handle a 500hp big block stroker. He told me he could do it and that 700r4's were capable if built correctly and he was right. It was built with heavy duty clutches and a corvette servo. The motor is just over 500fpt. He also built the 700r4 on my son's 87 k10(405hp/420tq). Both were rebuilt as carry-outs for $800. I've had zero issue with either, shift great. On our '86 K10 "LS" swap we'll be installing a 6.0 LQ4 motor. I'd assumed I'd just rebuild the stock 700r4 in it but I've researched that the 2wd-4L80 will mate to a NP208 transfer case, something about shortening the shaft. I'm not looking for an LQ4 with a 2wd 4L80, it's a no-brainer for me considering what it will cost to rebuild and adapt the 700r4 to the LQ4.

 

[jorlain]

If I were to go with an auto, I'd definitely go with a 4l80e. You can get pullouts at most salvage yards for $400-500. Panel trucks and utility vans came with them aplenty with varying engine configurations. Not that a 700R4 wouldn't work. I rather like them for what they are, but you do have to put some money into them to keep them from burning up 3-4 clutch packs all the time, especially behind any power.

 

[Battlac40]

I've got a 700r4 that my transmission guy built for me to handle a 500hp big block stroker. He told me he could do it and that 700r4's were capable if built correctly and he was right. It was built with heavy duty clutches and a corvette servo. The motor is just over 500fpt. He also built the 700r4 on my son's 87 k10(405hp/420tq). Both were rebuilt as carry-outs for $800. I've had zero issue with either, shift great. On our '86 K10 "LS" swap we'll be installing a 6.0 LQ4 motor. I'd assumed I'd just rebuild the stock 700r4 in it but I've researched that the 2wd-4L80 will mate to a NP208 transfer case, something about shortening the shaft. I'm not looking for an LQ4 with a 2wd 4L80, it's a no-brainer for me considering what it will cost to rebuild and adapt the 700r4 to the LQ4.

@Rhett Croley Can you send me any details you have on the LQ4/4L802wd/208 setup? I have $900 into a 208 that is behind a worn-out 350C-lockup. I am very interested!

 

[Craig Nedrow]

The 350TH, 700R4, 4l60 and 4L60e all have similar internals, many parts exchange. Go here: https://www.sonnax.com/
Will take as much HP as you can throw at is, until the input shaft breaks, then go to an M300 shaft or simular. they are easy to build at home, go to Youtube university, many excellent videos.

 

[shiftpro]

With a 4L60 or 80, you will need a pricey shift controller.

 

[jorlain]

Jake's Performance has a neat little shift controller that essentially makes it perform like a manual valve body. The car will be in whatever gear the shifter is in. It's not too crazy a price - $185 or so. The downside is that it's at full line pressure all the time so the shifts are going to be a bit on the firm side, depending on your converter, etc.

https://shop.jakesperformance.com/shop/ols/products/4l80e-manual-control-box

 

[Dale A]

If your C10 is clean and bright, I too, would leave it as is. I am biased a little, that is my favorite year, If you are planning on restoring the truck you might just consider a 350CI w/ a 400 or 350t. The combo is fairly inexpensive, easy to find and easy on the wallet for parts. A little mod here and there and you'll have a truck that's classic and burn up the rubber now and then.

 

[jorlain]

Unfortunately, the truck is riddled with rust and will be receiving some donor pieces and a fair amount of patch panels. In the end, there won't be much that's original to the truck. The good news is that the box seems to be in much better shape than the rest of it, with just a few rust spots in out of the way areas.

 

[shiftpro]

Jake's Performance has a neat little shift controller that essentially makes it perform like a manual valve body. The car will be in whatever gear the shifter is in. It's not too crazy a price - $185 or so. The downside is that it's at full line pressure all the time so the shifts are going to be a bit on the firm side, depending on your converter, etc.

https://shop.jakesperformance.com/shop/ols/products/4l80e-manual-control-box

There's a fellow in eastern Canada who makes them and they cost I think around $80 Cn beaver bucks... If anyone is interested PM me...

 

[Catbox]

What about just putting some boost into the 250?

Nothing crazy, just 7-8 pounds would make it peppy and totally different.