The Stovebolt Site Forums The Shop Area Engine Shop two piece driveline to one piece conversion.

I am wanting to convert my two piece driveline to a one pice. Any one out there have any ideas, or maybe have done this themselves. Any tricks will be very helpful. Thanks for replying.

What truck? There are some good reasons for running a two piece driveline, and the longer the wheelbase the more sense it would make not to change it.

The longer the driveshaft, the more critical balancing is. The faster the driveshaft is spinning, the more critical the balancing is. I can understand if weight is an issue and you were switching to carbon fiber or aluminum on a drag vehicle, however on a daily driver, I would not do it.

Go to the OldgmcTrucks website. The guy that runs the site, Rob (Oldcarkook) did this modification on his 3/4 Ton. He had some initial problems but apparently all is well now.

Grigg has a good tech article in the Tech section that explains how to properly set up a custom driveline. If you run through all the calculations in the articles provided, it will tell you what critical speed and balancing requirements would be necessary. Additionally, this might help you decide if it's something you want to go ahead with. Good luck.

Sorry I forgot to mention the model. Its a 66 C10 lwb

I also have the 2 part driveline. I want to go back to the "three-on-the-tree." Current set up is on the floor. The thing I notice is the transmissions are different. The 3 speed
T-5 tranny is longer. The tranny in the truck is very short. Can you keep the 2 part for the longer transmission or can you get a smaller driveline that attaches to the longer 3 speed tranny?
Thanks! I have a 1957 Chevy 3100.

This is what you need to know:
http://www.stovebolt.com/techtips/driveline/setup/index.html
And get out your calculator,

Grigg

Grigg,
You are a life saver! I was getting sandbagged by this shop and I knew there were other choices on this driveline...I will read up and give it a go! Thanks a bunch! Jon S.

I have a '62 SWB. I was surprised to find a 2-piece behind my sm 420. I am switching to a t-5, and prolly will go to a 1 piece. My worry was the slip yoke. I'm not sure if the flange type is mandatory with a two piece or not. A local driveshaft shop said they would shorten the 2 piece for around 175.00, but I can buy a used 1-piece for maybe 40.00.

As the former owner of a driveline shop I have many years of experience at building drivelines. These are a few things I leaned along the way.

Here are some very basic rules to be used a guidelines:

1. total length is from ctr/ctr of joints
2. 3" tube diameter is generally considered the minimum for automotive gas engines
3. 54" length maximum for gasoline which may require 3.5" tube in some instances
4. larger tubes need heavier wall thickness, i.e, 3"x.065 is popular but .083 & .095 are available, depends on the joint series, speed and available end yokes.
5. joint angle must be equal and cancel out each other.
6. 65" maximum length for diesel units - 3000 max rpm, usually 4-4.5" tubes
7. when replacing a driveshaft always have the builder use a tube & yoke [censored]'y which is much less $ than a tube and two weld yokes, This is because there is only one yoke to align and weld.
8. joint series cannot be mixed in any driveline
9. All yokes must be in phase
10. carefully assembled and welded drivelines do not require balancing which is a production consideration. Tolerances must be tightly held however.

When replacing a transmission the new one must have the same series of joint as the old one. So if the 4 speed has a 1310 series, (very common) and is shorter than the replacement tranny, uses a 2 piece driveline then it may be possible to go to a longer transmission assuming the new tranny also has a 1310 series and use a one piece shaft IF the OAL is still acceptable and angles are within specifications.

A complete new 1310 shaft might well be $200+ but a tube & yoke [censored]'y with a re-used slip stub shaft should be 25% less. Often u-joints can be re-used as well if they are in good condition, are carefully inspected and re-assembled.

Small dents do not usually cause concern and larger ones call for a tube replacement. Drilling holes in the dent and pulling them out will mean rust inside the tube, a no win situation.

These are all general information items and not meant to be specific to any particular vehicle. Most driveline rebuilders know their business and will not take advantage of a potential customer so don't jump to conclusions about them unless you have ALL the facts. That's good advice for virtually everything on the internet IMHO.

Thanks Dave, some good rules of thumb(s?).
Only two I am curious about are 8 and 10.
#8, I had never heard that the joint sizes/series could not be mismatched. I have done it with no ill effects (yet), and in considering how the joints operate and behave I can't think what would cause a problem. What am I missing?
#10, Even if carefully assembled you should still have your shafts checked for dynamic balance at the highest RPM you will be turning it, and correct the balance if needed. It may be really close but it can't hurt to check, and may save some time and money in the long run.

Dave has provided the short answers, for the long ones check the manuals in the driveline Tech Tip, they fill in the blanks and remove most of the guess work. Also find a good driveline builder, and pay for their good work and advice, it's their business...

Grigg

Tranny
Here is the tranny I have in my truck. Can some one tell me what type it is? I also have a photo of the 3 speed I want to put in New tranny I have the 2 part driveline. Can I just get a shorter driveline from the tranny or do I have to replace both drive lines? Thanks! drive line

It looks like you should be able to use your original rear shaft and carrier bearing.
The front shaft you would need shortened to work with the new transmission.
Then double check the geometry and shim as necessary to make the angles right. http://www.stovebolt.com/techtips/driveline/setup/index.html

For a two shaft system the first shaft needs to have it's centerline 1 degree down (or up) in relation to the transmission/engine centerline. With that 1 degree the inboard yokes on that shaft need to be in the same orientation. The rear axle pinion centerline then needs to be parallel with the centerline of the first shaft.

Grigg

Thank you Grigg,
Can you tell what type of tranny I have in the Chevy at this time? Tranny

Appears to be an An SM420... and quite frankly I can't understand why you would choose the three on the tree over an already installed 4 on the floor??? By choosing the three speed you gain nothing, and you loose a good low first gear and a firm reliable shifter.
I suppose if you want original, and it had a three originally, then that's one thing, but for a good usable easy to drive truck, the 4 is my choice of these two options.

Grigg

Hey Grigg,
Yes..I am a die hard 100% stock guy. My pop got this truck new and I recall shifting when I was very young with the 3 on the tree. I plan to restore the truck now that my father passed and I would love to return it to the original way. I know.. call me crazy!

I actually like the column-shifted 3-speed and would have it in my 1-tonner if it made sense - maybe with an electric O/D - because I like shifting them better than the floor-shift, but I would occasionally end up slipping the clutch pretty good to get going, and so my stump-puller first gear is of some use. Then, too, I have geared my truck higher for better road speed, so the low gear is of even more use now.

I had a '73 one ton van with two piece driveshaft, when I put in an overdrive trans I got a shorter front section at a wrecking yard. The factory had two lengths for the front section, the back parts were all the same. It was an easy swap, you should have no trouble.

Yes,
I think I am going to go with T-5 Tranny 3 speed and the 2 part driveline. Thanks

Well I have not modified too many drivelines, but I did work at a driveline shop for quite a while and if you really did want to change it (which i recommend not) you take your drive shaft to a specialty shop and what they will do is cut a length of tubing and weld your mateing yokes from the old drive shaft to the new, also they way you measure a driveline is from the center of the u-joint bearing cap and from weld to weld for good measure. I also recommend measuring from the tail shaft of the trans to the mateing yoke on the differential and based on your ride height you will get the amount of end play you want your slip yoke to travel. for a stock chevy c-10 i would go with anywhere from 1 1/4 to 1 3/4 inch of travel but only if your slip yoke splines are between 4 to 5 inches if is smaller step it down to about 1 inch or less. these measurements are to be taken prior to drive shaft welds are completed.

OK gang,
This is my new thought. I am returning the 3 speed tranny back into the 57 Chevy. Can I keep the 2 piece drivelinethat is in the truck already or do I have to go back to a one piece?
Thank you.

I have a 55 2nd 3200. I changed my 3 speed on the column to the 3 speed on the column with OD. There was no difference in length - I used the original drive shaft. It is a one piece drive shaft. I do not know why you have a two piece one?

UnklRod. I do not know if this helps or answers you question. Just my experience.

Dennis,
Good question. I know my dad removed the 3 speed back in the 70's and put the shifter to the floor. I am thinking that is when he used the 2 piece driveline. My problem is the 3 speed tranny is longer than the 4 speed that is in the truck now. If I kept the 2 piece, the driveline coming off the tranny would be very very short. When I get to that part of the restoration I am sure I will figure it out. Thank you for the thought! Jon