factory 1pc driveshaft lengths, pulling 3 sp, swap in used 4 spd if I can get a shaft

[Chuck78]

SM318 is acting up, and don't have the time to convert my Ford Tremec 5 speed to a GM and then swap it into my truck with a lot of fab work involved... My dad has a Saginaw 3.44 first gear 4 speed out of a 74-ish Camaro or maybe Monte Carlo, but it's approximately 21-1/4" from bellhousing to end of tailshaft housing (22" to end of tailshaft). My SM318 is only about 16-1/2" or 16-5/8" long, so obviously this won't work without chopping the shaft.

Are there any combination of chassis lengths, rear ends, and transmissions in our trucks that would lend me a 1 piece driveshaft for this Saginaw's length that will bolt into my 62 GMC 1000 panel truck without modification??? I have the GMC-only Dana 44, not sure if it's nose is any different length than a GM unit. That would be a real easy swap to be able to just bolt it up and to, with the addition of a floor shifter and deleting the column shift linkages. I'd still want overdrive in the future, but for now, with the time I have, this would be a great swap that I could do in an evening if I had a driveshaft.


Thanks,

Chuck in Ohio
1962 GMC 1000 panel truck
305D rat rod daily driver part time work truck

[Chuck78]

My truck is on part time, large hauling only duty (use the Subaru wagon or VW rabbit diesel truck for the rest) for a while until I get the time to swap in the 89 Suburban disc brake crossmember (my $120 each ((times 3!!!)) ball joints are shot on the 62 torsion bar front end, the 89 Suburban crossmember uses a common 1973-91 $9.99/each ball joint!), and my SM318 3 on the tree has a bad first gear, makes a clunk-clunk-clunk-clunk nonstop in first, with clutch in or out...

I have a Tremec TR-3550 for my future 71 RS/SS Camaro project, and a second one used 5,000 miles from a Mustang to eventually put into the GMC truck, but it not only requires getting another driveshaft to shorten about 7-1/2" from the current one, and add a Tremec-standard Ford C6 yoke to, AND custom make a crossmember for (SM318 uses no xmember) as well as buying a Tremec speedo cable adapter and adding a mid shifter kit to, but I also have to pull the Ford input shaft and input bearing retainer and install a GM and drill the GM bolt pattern into the blanks on the universal case.... Winter project for sure, after I get the house remodel under control....That's a lotta work!
This would be fantastic if I could just throw in this tranny with a different driveshaft and try it out. Also would be good info for others looking to ditch the 3 on the tree for an easy factory 4 speed swap.

[Chuck78]

I am thinking that I remember the Muncie/Saginaw/T10/ST10 being the same length in a Camaro as the TH350's installed in Camaros. Then I looked up a thread on hotrodders.com and apparently there are three lengths of tailhousings on TH350's, 6", 9", and 12". Not sure which came in a 60-66 truck, but that would be excellent if I could get a stock 60-66 shaft that uses the same U-joints and is a bolt in.
I could go to All City Auto Wrecking and sift through their massive pile of driveshafts, but who knows what vehicles they may have come out of, and how to ID u-joints without knowing what vehicle they came out of. Someone sell me a shaft!
I have a stock 70-81 Camaro driveshaft, but surely the panel truck requires longer.
I think it.s a 3.50 first gear Saginaw after reading that hotrodders.com post.

[raycow]

Your Saginaw is the same length as a 6" TH350. The problem is that no TH350 came in anything until 1969. You have a short SM318 which is the same length as used in 58-64 Chev passenger cars. There is also a long SM318 which is the same length as your Sag, but I don't know what year trucks it was used in. My 60 C-10 came with a 4 speed, so that's no help.

You are on the right track with your plan to go to a salvage yard and measure the shafts. You already know the Sag is about 4-3/4" longer than your SM318. Measure your stock shaft center to center on the U-joints. Then measure the U-joint cup diameter and span (distance between the lockrings). This is all the info you actually need to find a shaft. The Sag takes a 27 spline yoke, so your stock SM318 yoke probably won't work (the spline changed sometime around 64-65). Fortunately, the 27 spline is the most common GM yoke there is.

The above procedure is the way I found my shaft when I did a T-5 swap on my 60. Remember, the shaft can come out of anything as long as it has the right U-joints. The one I ended up with fomerly belonged to some kind of Ford product. It was the right length and all I had to do was swap the yoke.

Ray

[MikeN]

Having a driveshaft shortened and re-balanced is really cheap...$50 or less at the shop I use here in the Atlanta area. Use the driveshaft you already have. All you need is a slip yoke that fits your 4-speed, which should be common and inexpensive.

[6863m]

I have put a new 350 with a TH 350 transmission and I placed the engine based on where the HEI distributor and fan fit. I did not give much thought about the drive shaft because it came out of the same truck with the same combination.

I went to a drive shaft shop to build a new drive shaft because I was a little short and the one I had a little dent. He was not happy with my length of 72 inches and gave me all the warnings about vibration and would not stand by his shaft and I had to accept no warranty.

[andyh1956]

what rear axle ratio do you have in your truck now? the deep 1st gear ratio in the saganaw you have will be a bear to drive with a deep rear ratio. it will be like having a granny 1st gear, and if you have a 3.73 or 4.10 rear ratio you may be able to skip 1st altogether.
andy

[Chuck78]

The tag on the diff says 3.07:1, but I think the rear was rebuilt at some point in time with deeper gears, and I am thinking that it may possibly have something in the 3.42 range. Highway speeds are revving the low rpm 305 V6 pretty darn high for an engine not meant to go over 3700-4100 rpm's. 3rd gear at 35-40mph seems like a real nice cruising speed as far as the sound of the engine hitting it's happy spot of low end torque.
You can't rev the GMC big block V6's very high, but they sure are some serious stump pullers and haulers.

I don't want to have my shaft shortened yet because I would eventually like to put in one of my tremec's, which will require shortening it again, and I'd like to have a backup trans and matching driveshaft in case something went wrong with the 5 speed, or if I were to sell the truck and keep the 5 speed.

[Chuck78]

As far as a bear to drive, I think it'd be easier than an NV4500 with a 5.00 somehting first gear, and isn't the SM420 or SM465 as deep as 7.-- in first???? It'd give me an extra boost off the line but I'm sure with my gear range it will be manageable.
Right after I was born, my dad bought a brand new 79 Ford F250 with the 351 big block and 4 speed that I have a lot of childhood memories of. Not sure what trans it has, but it was a 0-6 mph first gear, and he'd often just take off in second gear with it by letting the clutch slip just a little off the line.

[raycow]

Originally Posted by Chuck78

The tag on the diff says 3.07:1, but I think the rear was rebuilt at some point in time with deeper gears, and I am thinking that it may possibly have something in the 3.42 range. Highway speeds are revving the low rpm 305 V6 pretty darn high for an engine not meant to go over 3700-4100 rpm's.

It is relatively easy to find out your actual axle ratio.

Put matching marks on the pinion yoke and differential housing. Jack one rear wheel off the ground, put the transmission in neutral, and the parking brake off. Turn the wheel exactly TWO revolutions and count how many times the driveshaft turns, estimating any fractional turn as closely as possible. That number is your axle ratio.

If the wheel is difficult or impossible to turn, you may have posi. In that case, jack both rear wheels off the ground and turn either of them only ONE revolution. Count the driveshaft turns the same way as for an open rear.

Ray

[andyh1956]

i have two trucks with NV 4500s- one with 4.10 & another with 3.42 rear axles. i never use 1st gear unless i have a trailer tied to them. good luck!
andy