JimMueller

iTrader: (9)

I'm having the u-joints replaced on my factory aluminum driveshaft. To ensure I don't need to take it off again to have it balanced, I requested they balance it before I pick it up. They said that the shaft never turns as fast as the motor, and that driveshafts are never balanced over 2000RPM on the balancer. Does that sound right?

Carl at CRP

iTrader: (9)

No it is incorrect. The driveshaft is spinning faster than the engine anytime Your trans is in overdrive.

Many companies with older balancers are limited to 2000RPM, most performance driveshaft companies have balancers approaching 10,000 RPM.

Carl

JimMueller

iTrader: (9)

What's the likelihood that putting on Spicer U-joints will throw the balance out of whack? I don't have any idea if there's 'performance' balancer anywhere close to where I live. Suggestions on where to send it for a performance balance?

Carl at CRP

iTrader: (9)

I would not have a driveshaft balanced after replacing u-joints. Difficult to think of any reason to do that.

Carl

1 FMF

iTrader: (1)

on the T56 manual transmission, 6th gear is a 0.5 to 1 ratio so the drive shaft spins exactly twice the amount of revolutions your engine rpm's in 6th gear. so if rpm's in 6th gear are 2000 (your going around 85-90 mph) your drive shaft is spinning 4000 rpm's.

for an automatic transmission 4th gear ratio is 0.7 to 1 so 2000/0.7 = 2857 drive shaft rpm.

my guess is your drive shaft shop doesn't do enough business so they have a cheap balancer that only does up to 2000 rpm. but the way you described what was told to you they are either lying to you to get your business or they are incompetent. nearly every car has an over drive transmission, and over drive by definition means a gear ratio less than 1 which means the drive shaft will always spin faster than the engine. for them to say it never does is a big red flag.

and like said there is no reason or need to balance a drive shaft after doing u-joints.
what you should do is mark which way the transmission yoke goes on to the drive shaft and reinstall the same way, they are typically balanced with the drive shaft so if you install it 180° out there is the slight possibility the shaft + slip yoke might be slightly out of balance.

Blackpanther99

iTrader: (8)

Agreed with posts above^^ Theres no reason to really balance it unless you just want to do so. Next time look for a drivetrain shop that can high speed balance your DS.

JimMueller

iTrader: (9)

My aluminum shaft was a used unit and I have no idea what orientation it was installed on the original vehicle; I didn't mark which way it came off the tranny yoke either. Based on info above, I didn't have it re-balanced, thanks!

mikedamageinc

iTrader: (49)

Hey Jim, I realize this is an old post but did you find a resolution? I just replaced my u-joints and now I have slight vibes on the highway. I forgot to keep the slip yoke the same orientation, yep my bad. I was thinking of either changing the yoke 180 or finding a DS balancer if the yoke doesn't change it.

JimMueller

iTrader: (9)

Hey Mike, I didn't have it balanced after the u-joints were replaced and I haven't had any problems with the driveshaft. I didn't do the work nor am I familiar with that process, so unfortunately I don't know what to tell you.

RockinWs6

I move the slip yoke 90 degrees at a time until its smooth at most speeds. Just mark the rear yoke -ds and front yoke-trans, remove the ds at rear and slip the yoke out of the trans. Turn the frt yoke 90 degrees clockwise and then slip it back into the trans. Test drive- repeat until you are satisfied, if you still have issues you can rotate the rear yoke 180 degrees and start over OR use 2 screw type stainless hose clamps as weights to rebalance the ds. Good luck

01ssreda4

iTrader: (96)

Lord.......if your ds was smooth before and vibrates after then you reinstalled the front trans yoke 180 out. It only goes on two ways so its a 50/50 chance even if you dont mark it. The rear yoke on the rear end has its own weight and is neutrally balanced so take that out of the equation. The front yoke and the DS need to be balanced together. Some DS like ford or dodge may have a flange on the rear end of the DS so it would need to be put back together correctly also but fbodies are not like that. And that stuff about turning it 90 of how its splined to the transmission......dont fool with that sillyness.

dailydriver

Most shops around here CANNOT balance an aluminum alloy drive shaft, as they are incapable of welding the weights onto aluminum.

I seriously doubt any shop with an old style, low speed balancer would be able to either.

mikedamageinc

iTrader: (49)

Well I tried changing the front yoke 180 but no change. The weird thing is it is mostly in 4th gear, but not every time.

phoenix rises

iTrader: (3)

The shop I work at balances at 5,000 rpms or 6000 depending on application. And yes we recommend balancing after u-joints.