T5 swap & driveshaft length?

[67 twins]

I picked up a T5 from an S10 that I plan on putting on my 67 C10 v8 truck that has a 3 speed in it now. Looking at what I need to make this work it looks like the T5 is about 3 3/16 in. Longer than the 3 speed (best as i can measure with the Tranny still in the truck)meaning I need a equivalently shorter driveshaft. After talking to the driveshaft shop & being quoted $350 to shorten my shaft, I started thinking.
The six cylinder trucks mount the engine & transmission further back in the chassis so a six cylinder 3 speed truck should have a shorter shaft. Well after measuring what I could it looks like the transmission crossmember in the 6 cylinder trucks sit somewhere between 3.4 & 3.7in. Further back.
I'm thinking this is close enough that a driveshaft from a 6 cylinder 3 speed truck might be just what I need. Anyone tried this before or would anyone like to comment?

[gmc684x4]

I am surprised there is not a chart made up of the varies drive shaft lengths for our trucks
I am not there yet but looking at putting a 5 speed from a 96 c1500 into my truck build

[typerr]

I did the exact same swap of a WC T-5 into my 70 that originally had a 3 speed. I took exactly 3" out of the driveshaft but paid significantly less to have it shortened. I brought them the front half of the driveshaft with the u-joint and carrier bearing already removed.

[jocko]

Originally Posted by gmc684x4

I am surprised there is not a chart made up of the varies drive shaft lengths for our trucks
I am not there yet but looking at putting a 5 speed from a 96 c1500 into my truck build

There's probably not a chart because every truck is different - the amount to cut is not simply the difference in trans lengths, it depends on the suspension, ride height, etc. Driveline shops generally ask for the straightline distance from the rear tailshaft HOUSING face (not the output shaft) to the center of the rear u-joint - as measured while the truck is weight-on-wheels. Then they do their math and cut - provides appropriate slip yoke engagement amount and ensures it won't fall out when the suspension is unloaded when one gets airborne over the RR tracks - or, more likely, binds it into the rear of the trans when the suspension is compressed (when one lands )

I've noticed that driveline shops (or at least the ones I've dealt with) don't tell me how long it's supposed to be after I give them my vehicle's measurements, until they have it in hand and start choppin. Probably a good business model or folks would be sending in their measurements, then chopping and welding at home. Personally I'd always use a trusted driveline shop, no matter HOW good I might think my welding is... They generally do a much better job cutting, welding, and balancing than someone who only does it every once in a blue moon - money well spent.

If you are measuring a ds from one someone else cut for their trans swap - and EVERYthing else is the same - ride height, tire sizes, rake, and of course trans & rear - you could probably get close enough to cut yourself and be ok. But I truly think it's worth letting an experienced driveline shop do it, in which case, knowing the exact length measurement they are going to cut it down to doesn't matter, they do it and you're good to go. I don't like spending $ or farming out work on my trucks either, but sometimes, it seems to be a good idea.

FWIW, $350 is only a little more than I paid about 10 years ago, but not much. Seems reasonable to me.

[Ultrasummer]

I just got done doing this whole thing. I put a T-5 in. Once the engine and trans was in place, I then approached the drive shaft shop told them what I had. They asked me questions about certain measurements. I crawled under the truck, got all the measurements they asked for, and then they fabricated a new drive shaft for my application. Btw, my old driveshaft was a 2 piece. The new one is a one piece. $388.00 done....with piece of mind.