Rumble/Vibration from standing start? (1 Viewer)

[ScottsHZJ80]

I have tried searching but I am wondering if any of you can help me diagnose a vibration I am getting through the seat of my pants as I move off from a standing start (very scientific description eh!).

It sort of feels like really baddly scalloped tire(s), but goes away as soon as the vehicle is moving about 5 or 10 mph.

It doesn't make a lot of difference if I'm in 2wd or 4wd, although it does seem to be a little better in 4wd and does not seem to do it in low range as much, if at all. The fact that I'm feeling it through the seat, and that its worse in 2wd, makes me think its comming from the rear end somewhere.

All I have been able to find by searching is the rear tailshaft might need some work. Mine doesn't seem to have any slop in it at the unis, but I do have a new one to put in as the splines on the old one are worn a bit but not enough (I don't think?!?) to be causing this. Could a worn uni joint be causing this sort of thing without any obvious movement or slop? I would expect to be able to get some play be turning the shaft while lying under the car.

I'm kind of wondering what symptoms I would get from a failing diff, as I have only ever had them go BANG in very spectacular fashion on the trail!! Any help would be much appreciated. In the meantime I'll go and put this new tailshaft in and see if it helps.

FWIW I'm running BFG MT 33's which are not scalloped, and about as well ballanced as MTs get!

TIA Scott

 

[ScottsHZJ80]

Did I miss the 'We won't help the guy with the part time 4wd 80' thread (tongue firmly in cheek) Oh well

I put in the new tailshaft which has solved the rumbling vibration at low speed but have now got one at about 35 mph. Is it possible the shaft is in 180 degrees out? I can't see it would make a difference but don't know a lot about drive shafts and such.

 

[ScottsHZJ80]

So nobody wants to help with the vibration? Fair enough.
I guess my 80 is more 70 series under the skin with part time 4wd etc maybe I'll ask over there.

Anyway, I'm still wondering if anyone can give me an idea of what a failing diff feels/sounds like as replacing the tail shaft has not fixed the problem entirely. It sure has helped though

 

[sseaman]

have you checked/ changed the fluid in the diffs? also do you have a second det of tires you could try and see if the vib is still there?

 

[landtank]

it sounds like normal mud tire vibrations to me. Put on some ATs and see how they feel.

 

[ScottsHZJ80]

Thanks for your input guys.

Yes the fluid level is OK but I guess it can't hurt to change it as its almost due anyway.

The only other set of tires I have at the moment are a set of TSL Super Swamper 34x9.5x16 which are totaly stuffed and even worse as far as causing vibrations go. Having said that I will try rotating the tires on the car from front to back to say if that makes any difference.

One of the guys from 70 series tech suggested the pinion nut sometimes works itself loose over time, so I'll check that as well, although I had a pretty good look around while I was under there the other day and couldn't see anything unusual.

 

[archie]

Try letting the truck roll down an incline while in neutral and see if the rumble still occurs. This way you can isolate the problem and see if it is related to the engine, tranny or wheels. Try it also with the engine off also but you will have NO power assisted brakes so be careful on what's ahead! Keep us updated on the solution!

 

[ScottsHZJ80]

Archie

Thanks for jogging my memory. The vibration goes away almost completely when I put my foot on the clutch. This is what led me to think it was connected to the drive line rather than tires, but I'll try a tire rotation anyway as it is about due for one.

 

[photogod]

"The vibration goes away almost completely when I put my foot on the clutch"... Is it possible that your rear main seal has dripped on the clutch plate and it is slipping at startup? That has happened to me before on various other vehicles that I have had sticks in. Possible damaged or worn clutch plate???

 

[ScottsHZJ80]

I'm really hoping it's not the clutch and I'm pretty sure it's not the rear main seal, as I replaced the clutch and the rear main about 25 k km ago, but anything is possible. When the rear main let go last time it poured oil (1 quart every 1500 miles or so) everywhere, which it certainly isn't doing now. I'll try looking harder at the rear end before I start worrying too much about the clutch, I really, really, really don't want to pull the 'box again as it is a complete PITA. Thanks for the suggestion though, and if all else fails I guess I'll have to look at that.

 

[photogod]

Throw out bearing? Did you change the bearing while you were in there?

 

[Tools R Us]

How much lift do you have? If the rear pinion angle is off, it can cause that type of under load ossolation and it's hard on u-joints.

 

[ScottsHZJ80]

Sorry about the lack of replies, I was away for a long weekend. No wheeling though

Throw out bearing? Did you change the bearing while you were in there?

Yep, did the throw out bearing and spigot bearing while I was at it.

How much lift do you have? If the rear pinion angle is off, it can cause that type of under load ossolation and it's hard on u-joints.

I only have 2" of suspension lift, and have been running the same setup for about 200,000 km so I would have thought that it would have been a problem before now if it was going to be.



Anyway, I have been over the rear end and can't find anything unusual, so I am starting to suspect the clutch and begining to think I may need to pull the gearbox again! ARRRRGH!!