'67 C10 SM420 to Turbo 350 question

[xtinc]

Hi all,

I'm new to the board and Chevy trucks. I recently purchased a '67 LWB with a 350/4sp. It's a little ruff, but overall in good shape. I'm not a big fan of the 4sp trans currently installed and want to swap it out with a TH350 Auto. I plan on purchasing a Lokar floor shifter to go with the trans.

Hoping someone could help me with a few questions
1. What size transmission shaft should I get short or long?
2. Can I use my current drive shaft?
3. Besides an auto flywheel, auto trans mount, Lokar shifter, transcooler, and fluid lines, will I need anything else?

Thanks in advance for the help.
Tom

[Americanrider]

Howdy from Washington! I'm a stick man myself so I'll leave the questions up to those who know better than me. It's best that you put your location up in the right top corner, never know which board member could be close by and it makes trading parts easier. Do you know if you have the stock 4sp transmission in it now? If so it should be a SM420, it's popular with the 4x4 rock crawlers because its strong & low geared. Whatever parts you take off become good trading material, so add to your list a single brake pedal setup. Also you might consider better brake hardware, a booster, power brakes, or disks up front.

[Tx Firefighter]

Originally Posted by xtinc

Hi all,

I'm new to the board and Chevy trucks. I recently purchased a '67 LWB with a 350/4sp. It's a little ruff, but overall in good shape. I'm not a big fan of the 4sp trans currently installed and want to swap it out with a TH350 Auto. I plan on purchasing a Lokar floor shifter to go with the trans.

Hoping someone could help me with a few questions
1. What size transmission shaft should I get short or long?
2. Can I use my current drive shaft?
3. Besides an auto flywheel, auto trans mount, Lokar shifter, transcooler, and fluid lines, will I need anything else?

Thanks in advance for the help.
Tom

Welcome Tom.

I'm not sure about which length of trans you need. I've never swapped a 4 speed to an auto, just 3 speeds. You can measure the length of your current trans and compare to the lengths of auto trannys to see how it compares.

This I know for sure though....

You're also going to need an automatic tranny crossmember. You'll notice the old 4 speed has a riveted in crossmember right underneath the bellhousing. That all has to be removed and the auto crossmember goes under the rear of the auto tranny. The bolt holes are already in the frame. It's will take 8 bolts and nuts to hold it in to the frame.

If you starter is the original type which bolts to the standard bellhousing with 3 bolts, you'll need an automatic trans type of starter that bolts to the block as well as the 2 special long starter bolts to go with it.

You'll need new bolts for the auto trans flexplate. The original standard flywheel is much thicker and takes longer bolts than the auto one does.

You'll need the 3 special bolts that hold the torque converter to the flexplate.

Be sure and remove the old standard trans pilot bushing out of the center of the crankshaft. The auto trans does not use one and if you leave it in place, it will not allow the torque converter to fully seat up to the engine.

[xtinc]

Thanks for all the info, I'll update my profile and post on my swap progress.

[Longhorn Man]

These trucks came stock with the short shaft, so if you were to grab a short shaft Th350, then you could possably save a few bucks on drive shaft modifications by getting a strock th350 equipped drive shaft(s)
However, other than the drive shaft, there is no reason to not get the long tailshaft version. They are more common, and if you are thinking of a one piece drive shaft, this will shave off a few inches which can make it a $200 ordeal instead of $500.
Your parts list does look to be about right. The pedal assembly doesn't need chainged...the assembly is actually the same from one to the other, the only difference is the clutch pedal is removed for the automatic driven truck.
you may or may not need a new speedo cable too...small detail, yet makes going through the local speed trap much less nerve wrecking.

[krue]

Welcome to the board from South Mississippi! Check out our FAQ Submissions page for lots of good info!