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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: bobcooter on December 16, 2009, 03:37:44 pm
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I have a 79 C-20 with a TH-400 and a two piece drive shaft. I have been toying with the idea of replacing it with a one piece driveshaft. I have a couple but they are either too long or too short. One is out of a 77 C-10 shortbed ( too short by 1 1/2" and not very strong looking for a C-20) and the other is out of a 78 GMC C-15 long bed with the TH-350. That's why it's too long. . My question is, surely Chevy built some C-10 longbeds with the TH-400? That would be an easy swap after matching the crossover u-joints. Any thoughts.. There a place down the street that will shorten one for $100.00 but i'd rather skip that step if I am able to. Any thoughts? Thanks,
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From most of the data I have, most Heavy duty trucks 3/4t and up (and some hd 1/2's) recieved 2 piece driveshafts, because of their strenght and because of load.
If you really want 1 driveshaft, it is best just to have one made instead of trying to find one as you would need one out of the exact same truck to work.
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Yeah, well I don't do any hauling or towing. I measured eveything and if I swapped over to the TH-350 and used the shaft I have it would work nicely. I just don't want to change transmissions.
Thanks,
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Anything wrong with your current driveline? Whats the advantage of a single over the 2 piece. Just asking. Both my 3/4 have 2 piece, and my 4 half tons have singles.
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Far as I know the only advantage of a one piece is less U-Joints to service and replace. Maybe, maybe less driveline noise. Somebody once told me one pieces rob less hp, but I dunno.
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Thats what I am thinking Layne. I less u joint, less carrier bearing and about it. One big advantage to a 2 piece is less wear on the on the output shaft and seal of the trans too. Although that can also work in reverse too in some cases. I like a 2 piece when its done right and balanced. Many people do not mark them if they seperate them, and it can makes things a bit rough at times. I always stamp arrows on my 2 pieces when pulling them apart to be sure they go back together the same way.
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I don't know really. I just had some driveshafts lying around from some half ton trucks and thought about replacing the two piece with a one piece. Sometimes I think it's the "quest" for a part that gets me going. The two piece works fine, but I think you may get a little more power to the ground with a one piece. The thing is, I really doubt the difference is noticeable.
I 've had a two piece before on a Longhorn and didn't really ever have any problems except the carrier bearing going out.
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U-joint angle and balance.
Quoted from UTI Heavy Duty Truck Systems 4th ed:
"The longer the driveshaft, the greater the weight and therefore the greater the radial forces, especially as driveshaft rpm increases. At high speeds, balance becomes more critical. This why manufacturers limit tube length. For example, at 3,000 rpm, the length of any single driveshaft section, measured between the center line of the u-joints at either end, should not usually exceed 70 inches."
You also have to take in consideration the working angles of the driveline throughout the entire range of movement of the rear axle. The shorter shafts with more joints will have less of an angle, and permit a higher working speed (while also ensuring longevity for the joint and the rest of the driveline) vs a single long shaft with severe joint angles.
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We watched a movie in school about driveshafts. Pretty interesting stuff. Scared me enough to spray paint a dot everywhere on the U-joints and couplers and whatnot.
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Then you ask yourself, so what is the differance in a 1/2 ton and 3/4 or 1 ton that the 1/2 ton gets a single but 3/4 and 1 ton get 2 piece. Above would explain that, if you consider a 3.73, 4.10 and 4.56 rearend ratio, that shaft is going to be turning alot more rpms than a half ton with 3.42, 3.08 or 2.73's. Also the load weight and geometry when the truck drops too must be taken into consideration.
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We watched a movie in school about driveshafts. Pretty interesting stuff. Scared me enough to spray paint a dot everywhere on the U-joints and couplers and whatnot.
What does spray painting a dot do?
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Until he responds, I'll take a wild guess and say it has to do with balancing if taken apart, and to see if anything has moved or twisted. I use a metal stamp kit and hammer, and put marks on 2 piece drivelines, to make sure they go back together EXACTLY the way they were taken apart should the 2 pieces become seperated.
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I think hotrodpc is right. a driveshaft is balanced, whether one piece or two piece. A two piece will be out of balance if its put back together wrong.
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An unbalanced driveline can cause a few differant problems. 1 being vibration and uncomfortable for the passengers, but that is the minor issue. It can also cause premature tailshaft bushing and seal wear in the trans, and can also cause pinion seal wear and premature pinion bearing wear. Also can wear out U joints and carrier bearing too. Just best to keep it balanced. For what its worth, it really does not cost alot either. Trying to go off memory here, but about 10 years ago, I took my 2 piece driveline out of my 93 Ford E-350 Retired Ryder box van, to the driveline shop. I had them replace all 3 u joints, new carrier bearing, and balance both pieces. They considered that a total refurb on the driveline which actually it is, so they also had vatted it, and painted it nice and shiney black. If memory serves it was like $138 and it was like a brand new driveline again. I didn't think that was to bad for a 2 piece heavy driveline like that.
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Witness marking the driveshaft is known as driveshaft phasing. It is critical to maintain proper balance. The other important thing to do is witness mark the companion flanges so the driveshaft goes back in the same way it came out. The most important reason for this is to ensure no new noises or vibrations arise after R&R. Even if there is an existing vibration people tend to get used to them. If the pitch or rpm changes after you R&R a driveshaft you will get the infamous "ever since you worked on my car..."
We had a thread on this a while back
http://forum.73-87chevytrucks.com/smforum/index.php?topic=10814.0
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Yep! What everyone else stated! :D I couldn't remember it, but I was phasing it. Thanks Vile
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I see I really opened a can of worms with this one. But you guy's gave me some food for thought. Especially on things like drive shaft angles and RPMs. I my mind the longer one piece shaft would have less angle than the back end of a two piece shaft. I also wonder how much RPM difference exists between a 12 bolt rear end with a 8 7/8" ring gear and 15" tires vs. a 14 bolt rear end with a 9 1/2" ring gear and 16.5 tires? I have 3:73 gears so I guess it does turn pretty fast.
My truck is a "retired" work truck and now pretty much leads a "life of leisure" if that's possible for a truck. LOL! I drive it to work everday but I don't tow anything and the biggest thing I've hauled so far was a Powerwheels Mustang for my Grand Daughter's Christmas. I was thinking I could keep the two piece and reinstall it if I ever buy a travel trailer or big boat something.
Thank you for all the input but no one however, answered my original question: Did Chevy build a half ton, long bed with the TH400? Thanks again for all the replies.
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I am sure they did but someone might have changed it down the road. They made both long and short tail shaft TH400. I have seen both in our trucks.
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I do not recall ever seeing a factory half ton long bed or short bed for that matter, with a Turbo 400 from the factory. All have been T350 if they were automatic that I have seen back in those days. From memory, what I remember, half tons got T350 and 3/4 and 1 ton got T400. The 3/4 and 1 ton got Turbo 400 regardless of engine size, so even if it were a small block. But if you got a Big block in half ton, it was a T400. I do not recall ever working on a factory big block half ton truck in this era, but I am sure they exist. But I think that is the only way you'd get a T400 in a half ton, is it were a factory big block 1/2 ton.
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Did Chevy build a half ton, long bed with the TH400? Thanks again for all the replies.
Lots of these trucks 1/2 ton came with TH400's
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Cool, I have never seen one, and I have worked on lots of these trucks. I build automatic transmissions, and yet to build a 400 out of a half ton. Done a few in 3/4 and 1 tons. Done lots of 350's though in half tons. Maybe because 400's last so long could be why. So now that makes me wonder if those 1/2 tons with 400's have a 1 piece or 2 piece shaft. Of my 6 trucks, 4 are half tons and all are 1 piece driveline w/ turbo 350 including the K10 that is a 700r4 w/NP208. That truck does not have a drivetrain in it right now, but I do have the rear driveshaft for it. Both of my 3/4 tons are Turbo 400 and 2 piece shafts. 1 being a factory 454 w full float 14bolt, 1 being a factory 350 with Semi Float 14 bolt.
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My 74 C15 came Th400 2 piece
My 80 C10 came Th400 1 piece
Both were long beds
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Thanks Guy's. I may still try it. If I do I'll let you know. If it fly's into a million pieces like Vile said, I'll let you know that too!
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Sounds good Cooter. Anyway you can mount a video cam under the truck? We want to see that carnage as it happens. I say its gonna be fine, no matter which way you choose to go.