R50 Propeller shaft run-out spec concerns

[donald]

SooOOooo... this past weekend I took on the feat of changing the u-joints on my 2001 Qx4 (4wd) on the rear shaft (Front shaft looks like I'll need some special skills to get the bolts out).

So, I did this all on my own, took me about 4-5hours from start to finish, changing both u-joints on the rear propeller shaft (drive shaft, for those who are picky on wording :p)

Long story short - there was a lot of banging and such with a hammer and a u-joint press to get the u-joints out. Actually, when I removed the shaft, the original u-joints were still good (no play, and roller-bearings seemed good). I decided to change them only because I had the new u-joints in hand, and had already removed the shaft.

Anyway - just took my highspeed drive today (ie. 65mph+) and I'm getting a very noticeable vibration at certain speeds (notably, 70mph and 80mph on the point). I read through the FSM (PD-5), and it reads

"If vibration is present at high speed, inpsect propeller shaft runnout first. Runout limit: 0.6mm (0.024in)"

So, 0.6mm is a VERY small amount, I'll agree.
My question is how "easy" would it be to knock or bend the shaft out of straight by this much? I worried all the hammering I did may have somehow bent the shaft out

[Leo1998]

Did you mark the propeller shaft before removing?

[Leo1998]

http://www.drivelinespecialist.com/Tech1.htm

This may help...check out the Phasing part.

[donald]

http://www.drivelinespecialist.com/Tech1.htm

This may help...check out the Phasing part.

good info. I'll try to crawl under the truck again and see if I can run the measurements. I really hope it's not a bent shaft

[miamiheat3332]

I had this issue few years ago. Random day in car it had vibration coming from the middle/floor and could be felt through the whole car.

Looked under car for a day, on the driveshaft there are welded weights from factory when they balance it, one of them had fell off.

Took driveshaft out and took it to a place that did driveshaft balancing. Installed it again and issue fixed..

Either that happened on yours, or how you said hitting it with hammer may have slightly bent/indented it somewhere.

Id say take it out and do what i did. It was only about 80-90 dollars i believe.

[racerken]

SooOOooo... this past weekend I took on the feat of changing the u-joints on my 2001 Qx4 (4wd) on the rear shaft (Front shaft looks like I'll need some special skills to get the bolts out).

So, I did this all on my own, took me about 4-5hours from start to finish, changing both u-joints on the rear propeller shaft (drive shaft, for those who are picky on wording :p)

Long story short - there was a lot of banging and such with a hammer and a u-joint press to get the u-joints out. Actually, when I removed the shaft, the original u-joints were still good (no play, and roller-bearings seemed good). I decided to change them only because I had the new u-joints in hand, and had already removed the shaft.

Anyway - just took my highspeed drive today (ie. 65mph+) and I'm getting a very noticeable vibration at certain speeds (notably, 70mph and 80mph on the point). I read through the FSM (PD-5), and it reads

"If vibration is present at high speed, inpsect propeller shaft runnout first. Runout limit: 0.6mm (0.024in)"

So, 0.6mm is a VERY small amount, I'll agree.
My question is how "easy" would it be to knock or bend the shaft out of straight by this much? I worried all the hammering I did may have somehow bent the shaft out

The Nissan service manual is a joke because the removal illustration has a guy tapping lightly with a hammer to remove the u-joints. After I completely damaged a u-joint via hammering, I broke down and drove the driveshafts to a drive shaft expert... There pricing is $45 for driveshaft balancing, 15 for each u-joint they replace. I'm lucky because I live 30 minutes away from Shaftmasters in Detroit and all they do is custom driveshafts and balancing.

Did you replace with new grade 8 nuts/bolts?

Things to try:
1. balance.
2. make sure all bolts/nuts are identical.
3. rotate yoke 90 degrees and test drive, repeat until you find the least amount of vibration.

I've never seen anyone straighten a drive shaft but I'm assuming it aint rocket science but it aint for home remedy.

[donald]

I didn't want to leave you all hanging, so here's a mid-term update

first - I'm still getting the vibrations at 60, 70, and 80 (especially when decelerating from 80+)

To answer some of the questions above:
1. Marking drive shaft? - yes I marked and replaced the driveshaft in line with the markings prior to removal.
2. balance weights? - the balance weights seems to still be there. I don't see any markings or indication where the weights might have fallen off. I still have 2 on the shaft, 1 near each end of the shaft.
3. identical bolts? - I purchased the bolts from Nissan dealership. The bolts and nuts all look the same. I haven't tried weighing them or anything.

What I've tried:
- verify u-joints are "zeroed" out by slapping a hammer against the joints (shaft removed) and double checking joints/pin-bearings are not stuck/sticky
- thinking that the connection orientation at the transmission side was out of place, I tried rotating the shaft 180' with respect to (wrt) the transmission splines [result: vibration still exists, no change]
- replaced the orientation and reverted back 180' on tranmission splines.
- rotated shaft at transaxle 90' [result: no change, vibration remains]
- rotated shaft at transaxle another 90 (total 180' from original) [result: no change]

So, now I think I'm going to cross my fingers and seek out a driveshaft shop. I haven't seen any mechanic shops strictly advertise driveshaft work, but I'll call around to different shops. There's a local transmission shop that has pretty good reviews that I may try and see if they can do anything.
I'll update with prices, and possibly a solution.

What I don't really understand is why the FSM suggests rotating the shaft 90' at the transaxle. I figure the shaft is balanced while the shaft is removed from the driveline.

thanks again!

[Leo1998]

Isn't there a center bearing/bushing for the propeller shaft. Bolts to a cross member and the shaft goes through it? I know on mine i have to replace it but haven't yet. I can see the boot torn and move the shaft around, so a lot of slop in it, could be your vibration and the shaft is fine.

[Leo1998]

Never mind, your Qx4 is 4WD.

[donald]

An update (Oct 2014).

So, i still have the vibration at certain speeds.

I was able to take the truck in to have it "diagnosed". Long story short - technician suspects the vibrations to be coming from road noise transferring into the truck/cabin based on the fact that I have poly bushings on all 4 rear trailing arms, in combination with the suspension lift I have in the rear (ie. the OME Medium Duty springs, but I have MD springs at all 4 wheels).

The shop tech did agree and noticed the vibration at specific speeds. The shop did not have a balancer for the propeller shaft, but the technician noted that the u-joint R/R job looked good and did not see anything adversely wrong. He also checked the front and noticed the wheels to be "loose" and suggested to re-pack the front wheel bearings with grease - but he did say that he didn't think the front wheel bearings would be the cause.

My worry is that I likely bent the yoke somehow (likely the either of the yokes at the rear joint) and it is mis-aligned and causing the u-joint cap to rub tight against the pin-bearings.

I do know that the u-joints do freely rotate; that is, with the shaft removed and not touching the u-joint - when I rotate the shaft the u-joint will freely rotate about the joint and shows no sign of "sticky" rotation, or slow rotation when the shaft is being rotated. This goes for both the front and rear joint on the rear propeller shaft.

My next try is to go to another shop - hopefully one that can test the balance of the shaft - have them re-do the u-joints, check the "trueness" of the yokes, bend them back if possible, and check balance of the shaft.

[racerken]

My Two Cents:

1. It might be the transmission? I started noticing a slight vibration at 68mph and discovered that coolant mixed with the trans fluid. (Typical problem with R51 - clamshell radiators unclams!) After flushing the fluid out 3 times, there is only a whining sound so I'm waiting for the transmission to die one day before rebuilding it.
2. Maybe it's the propeller shaft between the transmission and the rear differential which might be out of true - not straight... The run-out is not supposed to exceed .6mm for a 4x4. If it's off, you're supposed to rotate 90, 180, 270 and check run-out... If it's out, the shaft has to be replaced.

This is what the service manual states:
REAR PROPELLER SHAFT PFP:37000
On-Vehicle Service EDS001H1
APPEARANCE AND NOISE INSPECTION
Check the propeller shaft tube surface for dents or cracks. If damaged, replace the propeller shaft assembly.
Check the bearings for noise and damage. Repair or replace the bearings as necessary.
PROPELLER SHAFT VIBRATION
If a vibration is present at high speed, inspect the propeller shaft runout first.
1. Measure the runout of the propeller shaft tube at several points
by rotating the final drive companion flange with your hands.
Propeller shaft runout limit
4x2 : 1.02 mm (0.0402 in) or less
4x4 : 0.6 mm (0.024 in) or less
2. If the runout exceeds specifications, disconnect the propeller
shaft at the final drive companion flange; then rotate the companion
flange 90°, 180° and 270° and reconnect the propeller
shaft.
3. Check the runout again. If the runout still exceeds specifications,
replace the propeller shaft assembly.
4. After installation, check for vibration by driving vehicle.

PM me if you need the guide.