driveshaft vibes?

[domn8tr]

Reading my (quality) Haynes manual it says to scribe the ends when removing the driveshaft for re alignment upon installation. When putting in the dogleg we had to adapt the output flange with the freeze plug and nothing was scribed. also I don't know the history of the driveshaft and have a feeling the front and rear sections may have been swapped . How crucial is the alignment of flanges and front /rear sections of the driveshaft ?. I have a lot of vibration I'd like to clear up. I also suspect the support bearing is toast. Are these a bitch to get off.? I saw the bearing once on Fleabay for $75 anyone know where to get one cheaper? and are new rubber rings available for the bearing support? Thanks!

[datzenmike]

If yours is a 2 piece drive shaft, it may have been balanced together. If you split them apart you may alter the balance. If in doubt split it again and swap 180 and install and see if that clears up the vibration. Just changing the spline shouldn affect it.

 

Inspect the driveshaft for... undercoating. I can't believe how some idiot dealership dick over sprayed this crap all over one side of mine.

 

 

 

The center support bearing almost never goes bad, never seen a confirmed bad one. What does go bad is the rubber donut 'isolator' around it. They flex and slowly rot away allowing misalignment and vibration, mostly when accelerating.

[domn8tr]

When I bought the truck from SDSurf it had a 4 speed that was so loud I couldn't hear myself think. I put in a 5 speed but there's still a lot of noise especially in the higher gears. He did give me an extra driveshaft maybe I'll swap it and see if that makes a difference. My friend who cut the trans mount didn't quite get it right and the trans sits high. I had to work th trans tunnel to get to not rub. Would this bit of misalignment possibly be causing vibes?

[albyneau]

When I bought the truck from SDSurf it had a 4 speed that was so loud I couldn't hear myself think. I put in a 5 speed but there's still a lot of noise especially in the higher gears. He did give me an extra driveshaft maybe I'll swap it and see if that makes a difference. My friend who cut the trans mount didn't quite get it right and the trans sits high. I had to work th trans tunnel to get to not rub. Would this bit of misalignment possibly be causing vibes?

 

When scribing they're referring to the center slipyoke. The only time the ends can come into play in phasing is if the driveline's been improperly modified (1 piece), or not indexing that center slip yoke (3 piece). Like Mike said, carrier bearings rarely go bad in the protected invironment under our trucks. On a large truck (or 4x4) they're hangin out in the air/dirt/mud/rain/roadkill stream~ and I've replaced quite a few! Do mike's 180 degree test~ and while your under there (with a light) carefully inspect the shafts for newly exposed bare metal areas and failed spotwelds near the ends~ sometimes a d-shaft can just sluff off a balance weight. The trans mount may be an accomplice, but would not be a lone perpetrator~ depending on amount of movement from original location. Is the trans hitting the tunnel anywhere? Do you feel or hear the vibration? Have you checked the diff fluid??? The front pinion bearing can get quite a song going if its running low or has been run low on gear lube. Also if it's been lifted/lowered excessively to where there's significant ujoint angle change at the pinion~ it sideloads the front pinion bearing more, with the same noisy result as the lack of oil...

 

Scott

[domn8tr]

Thanks Scott! Very Informative . The trans was up enough that I had to pry and beat the sides of the trans tunnel until it cleared. I think more likely the two halves aren't aligned as my son and I had them apart during the swap. We did change the diff oil and there were shavings on the magnetic plug. I'll be hitting the yards in search of a 4;11 LSD diff soon

[datzenmike]

For best vibration free running the angle in should equal angle out. When there is a bend the drive shaft actually speeds up and slows down when turning. If the angles are the same the second U joint being 180 different will cancel the vibration.

 

 

Try lowering the back of the transmission.

[domn8tr]

Thanks mike! My friend did the cut and weld free so I hate to ask him to fix it but if swapping the driveshaft doesn't help I'll have to do it!!

[datzenmike]

Was it balanced???

[ggzilla]

Haynes is not talking about the center slipyoke balance! The Haynes Repair manual says:

 

The propeller shaft is carefully balanced to fine limits and it is important that it is replaced in exactly the same position it was prior to removal. Scratch marks on the propeller shaft and rear axle flanges to ensure accurate mating when the time comes for reassembly.

 

This is stock wording that's in all the Haynes manuals. My opinion is that genuine Datsun driveshafts and differentials are balanced and manufactured more precisely than most cars of the era, and what Haynes says here does not apply to Datsuns. Although it won't hurt to follow there advice I've yet to see a case where it mattered.

 

With some american cars of the 1960s they were so out of balance from the factory that the dealer would do an on-car balance (w/o removing the driveshaft) and in those cases, marking the flange faces is important. They didn't check what was OOB, they just balanced everythign at once.

[albyneau]

Keep in mind that mike's pic post is for illustrative purposes only! Equal angles at both ends is optimum, but minimal angularity is important as well, here's why~

 

 

If you find yourself on the path of driveline angles, here's a good place to start~

 

http://www.drivetrain.com/parts_catalog/drivetrain/driveline_angles_and_phasing_problems.html

[Brian D]

Also if there is too much pressure from the rear end pushing forward it can cause what you explain. With changing the drive shaft it could be applying to much forward force along with a incorrect pinion angle. Just a thought.