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Discussion Starter · #1 ·
All:
I have a question regarding drive line balance. Recently transplanted a new 727 and 208 into a manuel transmission vehicle for the wife. I understand drivelines should be installed in balanced orientation. Considering I swapped trannies marking the ends was not an option. I installed the drive line and took my chances. The truck ran fine for almost 3 weeks and then came the low hum from the rear of the vehicle. I went underneath this morning checking for loose u-joint bolts and diff/gearbox oil. All checked out fine. I did notice some transfer case fluid starting to drip out the rear seal suggesting driveline wabble. One option is to create a marking system and start the process of elimination by rotating the driveline until the sound goes away. It seems there are four possible configurations to choose from. My question is are there any rule of thumb approaches and how does one determine true balanced installation?. It seems impractical to have a driveline mated to a particular drivetrain. You should be able to swap out drivelines as long as they are installed correctly. Please advise.
Thanks for your time.
Cliff out
 

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what kind of vehicle did you do the transplant on? did you replace all the bumpers that the t-case and trans ride on? perhaps driveshafts need to be balanced. when they are unbalanced it leads to wobble, that sounds like your main problem.
 

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If your driveline wasn't correctly balanced to begin with, you would have noticed it from the beginning. Drivelines just don't unbalance themselves, unless the weights got flung off or the driveline receved damage. There can be other reasons for the humming noise you're hearing.

Since the t-case is dripping oil, I'd start there. It may have had a bad or worn out seal when you reinstalled it, and it maybe running low. Additionally if the bearings are bad in either your t-case or axle, the driveline could vibrate.

Ed
 

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ok what i think you are experiencing is your driveline being out of phase. the ujoints need to be installed parralel to each other

this is fairly rough drawing but should give you the general idea

other than that you might be having a ujoint go out on ya

ok i edited the pic, see later post

eric
 

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Discussion Starter · #7 ·
Intenseimages and JackedRamcharger: The slip yoke was never removed from the driveline so it shouldn't be rotated in reference to the opposite driveline end. Does it matter if you take the entire driveline and rotate 180? What happens if you put the transfer case in neutral and rotate the output shaft before mounting the driveline? Is the balance of the drive shaft relative to the outputs of the t-case and diff? Am I making this too difficult? Any comments or suggestions would be great.
 

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ok, when you did the swap, did you take the WHOLE driveshaft from the donor truck ??? Was the driveshaft ever taken apart ?? did it possibly get bent ??? Did one of the yoke arms get bent ?? (drop the driveshaft ??)

what engine was in the donor truck and your truck ?? if the donor truck was a 318 and yer truck is a 360 (or vice versa), then you have to swap torque convertors, as the 360 and 318 have different torque convertors (well, the 360 one has a special weight on it for balance).

Also make sure the mounts for the tcase are bolted down securely. I had one work loose once, and it gave me a similar vibration.

How much engagement do you have at the splined joint in the driveshaft ?? if it less than 1", that may be the problem too. Try pushing on the d/s at the slip yoke. if it moves more than 1/8" up or down, you may have a worn out slip joint.


You could put the rear of the truck up on jackstands, and try to see, with it in gear, if there is any obvious problem, like wobble (if you can disengage or remove the front driveshaft).

And that picture is confusing me.....the u joints should be in phase...IE if you were to lay the driveshaft on the ground, the yoke arms for the driveshaft should be in the same positions on both ends. They may not have been in phase before you got it. So if you have it laying with the yoke arm for the d/s at the pinion end straight up & down, the other end should be the same way.

Also look to see if it looks like any weights may have been knocked off. Often times, they are just a flat square of metal thatr is spot welded, and it ain't hard to knock one off.

Make sure the u joints are fully seated in the yoke arms, and that they are the right size too.

And IF you have a rear bearing problem with the tcase, it can give you the same symptoms.
 

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Lots of good advice here, so add this for more information:
 

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Nice chart, but it don't include the engine/trans. I had a vibration from 60 on up, and it was cuz of a 318 TC on a 360 engine. Swapped to the correct TC and it went away.

It would be a good idea to try and get a bit better/clearer pic of that and put it in the help section for driveline if it isn't already.
 
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