Hi guys,

When I put the dual transfer cases in my Pajero, I had 2 custom shafts made up, front & rear.

They both had to go back for a rebalance & the front one went back for a rebuild as it had 40thou runout.

The rear shaft has 11 thou runout at the transfer case end & the front one still has 12 thou run out.

I still have vibes when I run the car in 4wd highway mode, no vibes that worry me when I run in 2wd with front axle disconnected.

Heres my theory,

Most sources seem to indicate that 12 thou is 'within spec' for run out tolerance on driveshafts.

If so then why do I have vibes in 4wdh? My theorey is that whilst one shaft with 12 thou runout may not produce vibes, 2 shafts with 12 thou runout each however running at the same time, tip me over the tolerance level & hence I get vibes? What do you guys reckon?

The driveshaft guys say they cant get the tolerance any lower (cheap arses they are), so I am in discussion atm with Tom Wood over in the US to make me a custom front shaft.

I also believe that others who have done this mod, ie dual cases, have used the NP231 which doesnt have the highway 4wd mode, so shaft vibrations may not have reared their head since the NP231 doesnt run in 4wd on the highway. Does this sound reasonable/

cheers

I'm not sure what you mean by "4wd highway mode". The NP-231 is a dual range t-case with many applications.

As you have a dual t-case setup, I would look into driveline angle for your source of vibration, especially as the vibration occurs in 4wd.

Another possibility would be the vibration coming from within the T-case or the output shaft.

Use the site search at the top of the page to see several 4x4Wire article dealing with driveline angle like the link below...

http://www.4x4wire.com/tech/pinionangle/

Whats speeds do you get vibration at?

by 4wd highway mode I mean 4wd high range with the centre diff unlocked. I think you guys call it Active Trac. AFAIK the NP231 does not have a centre diff?

The vibes kick in around 80kph

Driveline angles are not excessive, in fact quite mild.

I just need to know if I should get Tom to make a shaft that has less that 12 thou runout

Okay, got it. There are several variants of the NP-231 and the NP-241 with creative names like Select Trac and Command Trac.

Anyway, your issues is with vibrations when you hit 80 kph (about 45-50 mph is I have the conversion right).

Tom Woods does produce a quality drive shaft. I am sure he can make one that is within tolerances.

As you have mild driveline angles, there are other factors that have could be contributing to you vibrations. I recall some past threads about vibration in the forums. Search for "driveline vibrations".

I have had vibration issues that were resolved by replacing the transfer case mount. I like to look for the simple (cheap) solutions before swapping high cost parts....

You could tell the original guys and see if they'll balance them again. I'd check the u joints for any play before they do. Something seems off if the second time you got the shafts back when they balanced them you had less vibration.

Tks guys, one thing I didn t make clear was that I am running an NP242 which is very different to the NP231, mine has a centre diff that can be unlocked & run in 4wd mode on the highway.

Sorry I didnt specifically say this.

Figured that after your clarification of terms. Like I said, the NP-231 and NP-241 are basically similar. There are severel model variants, mostly with internal gear ratios.

The NP-241/2 is known in the Jeep world as Command Trac and is a full time 4x4. The NP-231 is the most common.

Again, when you lock it into 4x4, you are fully engaging the front drive. If you get vibrations then, the factors are driveline angle, driveline balance, worn bearings, u-joints, front tire balance and alignment, loose or worn spring hangers. If the runout you measure is within factory specs, I would eliminate all other factors before focusing on the driveline.

I overlooked the question of where (how) are you feeling the vibrations? You said the when. If you feel it in the steering wheel, I would focus on the steering components such as tire balance, ball joints, and steering linkage. If you feel it in the console (at the shift lever) I would focus on mounting issues.

I have experienced vibrations due to driveline balance, worn u-joints, t-case mounting, and tires. Tires can be fine at low speed but cause vibration at high speed due to internal issues where the steel-belt is off center.

Thanks mate,

all was fine before the conversion to the NP242, ie I had no vibes from the front or the rear. Thus I can eliminate most of the usual causes.

The only thing I can really put it down to it the front shaft given that it does have 12 thou runout. I guess I am just gonna have to bite the bullet & get Tom to make a shaft for me.

I made a rear driveshaft in my garage with .006 runout and I never had it balanced. I didn't notice any vibrations so I just let it ride. I think the shop is giving you the shaft... They possibly cheaped out on the front shaft because they mostly don't turn all the time and they probably don't know you're running AWD.