67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

New here, so hopefully I'm posting in the right forum. I have a 67 Chevy C20. Originally 3 speed transmission (3 on the tree). I've purchased a TH400 (automatic) for conversion. I have the trans installed. Now comes the hard part - the drive shaft. Since the truck obviously isn't drive-able, wondering A. Do drive shaft specialist come out to measure? If so, does anyone know of a trust worthy operation in Los Angeles (323 area) or B. Can I measure it myself?... and how do I do so with accuracy (starting point, ending point)? Help. I'm lost. :chevy:

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

I found this website. Looks like good information here. I know nothing about the company.. Good luck as i will be in the same boat in a year or so when i do that swap!
http://www.dennysdriveshaft.com/how_to_measure.html

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

The one posted on that link in the last post is a good reputable company. They will tell you how they want the measurements. Would looking for a stock front half of a driveshaft not be a viable option? I know EVERYONE says to change out thew halves together but I just thought if you could find a used shaft it might be OK to use.
Welcome to the forums there is lots of good people and some really good truck help here too. Jim

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

For mine I measured the original trans (and bell housing) from where it mates to the engine to the end of the output shaft. I measure the new on the same way and subtracted the difference. In my case it was 5-3/4". I dropped the DS off and said shorten the transmission side 5-3/4". A few days later I picked it up and viola...perfect.

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

Many Thanks for ALL the great info guys! HUGE help! I guess I'm in the right place.

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

How To Measure A Drive Shaft
If you have changed transmissions and need to measure for a new one, it is important to measure from the face of the seal on the tailshaft to the flat surface on the pinion-yoke with the pinion-yoke installed and the car sitting at ride height. Changing to a billet pinion-yoke can alter the length by as much as 3/4 inch. maintenance

With this measurement, the driveshaft shop can create the complete shaft with the required slip-yoke and predetermined play for the slip-yoke. For most applications, 1 inch is more than enough for suspension travel. Do not let a shop talk you into leaving more play than that. Some transmission shops will insist on running 1.5 inches, which would be disastrous. With that much of the slip-yoke hanging out of the tranny, there could be less than 3 inches of splined yoke in the tranny, thus creating a wobble in the yoke, which would cause a heavy vibration at various rpm. Stick with the 1-inch rule and you will be good to go.

Source- http://www.hotrod.com/how-to/transmi...alancing-tips/

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

I have done this last month. Just know, your yokes will probably different on the T-400 transmission than the end of the drive shaft. You can use crossover U-joints. "While it can be done, using crossover U-joints is not suggested as a long-term solution. The smaller size basically becomes a fuse, and it will eventually fail." Is what I am finding.
Be prepared to replace the yoke on either the transmission or the drive shaft.
Mine is a 67' which had 3 on the tree. I went with a 396BBC / T-400 automatic. This is what I ran into. Hope it helps!!

Re: 67' C20 manual to auto trans, Turbo 400 conversion, drive shaft length??
 

This is where I am at. The yoke is different than the shaft. Any idea on a part number on that particular cross-over u-joint or will they know what I am talking about?