I've got a wobble!

[Ecoman]

Am I likely to have a viscous coupling on my 80? Where abouts is it? and what is its purpose? The reason I ask is that after some reading of various forums I seem to get conflicting information. Some say do away with it as its a waste of time and some swear by it and say its an excellent addition. The reason I ask is that the general consensus when they go wrong is a vibration or wobble and as you will probably have guesses my 80 has assumed a wobble!

The wobble at slow speed is almost like a tyre is out of true or a wheel is buckled but increase the revs and pick up speed and the wobble fades away. I have had the tyres checked and balanced and nothing is out of true. I have also had the 80 up on a ramp and checked the hubs while in drive and there is nothing loose or buckled. However, the wobble turns into a shudder when creeping along in gear at walking pace (stuck in traffic). It first became apparent when I had the injectors cleaned and the fuel system overhauled. With the increase of power came this shudder/wobble. I thought at first it may have been a cylinder or two low on compression but it seems that all the bores are spot on. When you take the transmission out of drive the shudder stops. Put it back in drive and the shudder returns. Again increase the power and the shudder becomes a wobble again and fades away.

Any help would be greatly appreciated

 

[adrianr]

You should have Viscous coupling do dad. Chris has a thread going on it on here.

Im not 100% but i would have thought either fails to work in which case you wont notice it in day to day driving or it locks up and it will be like having the cdl engaged and you'll get transmission wind up.

So if you can feel a wobble at those low speeds and since it started when injectors cleaned and fuel system overhauled id be inclined to examine those areas more closely.

how was fuel system overhauled exactly?

 

[Ecoman]

Ok thanks for that. I did see the thread you were on about hence why I started to wonder if thats what it could be.

Basically I had all the injectors reconditioned. I had the IP cleaned and calibrated and had the whole fuel system (except the tank) flushed out and pressure tested. I then had the pump refitted and timed up. I never noticed a problem before the work but put it down to an increase in power as the injectors were very bad before they were reconditioned and the IP was full of deposits. They concluded that someone must have run poor bio through it at some point. I did question the noticable shudder at the time and had the diesel specialists go back over their work and recheck the settings etc. They basically re-did their work and set up everything by the book but couldn't get rid of the shudder. They put down to an issue with the transmission but I'm not 100% convinced.

 

[Cptsideways]

I very much doubt its the VC

More likely engine mount, CV joint or propshaft

 

[Gav Peter]

Is there any noise associated with the 'wobble'??

 

[Andrew Prince]

or propshaft

I like this candidate Check u-js, and also input and output bearings in t/case and diffs. You haven't had any oil leaks from the t/case or front/rear diff inputs by any chance?

Seized VC seems unlikely to cause a wobble. Can we assume you've checked the rims for any clumps of mud on the inside or lost wheelweights? And the discs are all in reasonable shape, pads are within spec and none of the pistons have seized in the calipers? (Any signs of "blueing" on the discs would indicate heat build-up, possibly from a seized piston and the disc may be warped)

Looking forward to this internet diagnosis unfolding!

 

[Paul]

This also fits with the symptoms of an overgreased prop shaft sliding joint.

 

[adrianr]

Not sure fellas, hes feeling it a walking speed and its going away with speed?

If IP was out by a tooth when refitting would this not upset the overall balance of the engine and the low revs he is talking about>?

 

[Ecoman]

I don't think its propshaft or CV etc as it does it when stood still too. It gets more pronounced when the brakes are let off and it starts to roll forward under power. Put it into neutral and the vibration dissappears.

 

[Chris]

Sounds very like a problem I had. Not when driving really, but idling, very much. Just as a check, what's it like when you put it into reverse and try to back up slowly? Mine was atrocious. The cure was retipping the injectors. It went away completely then. I know yours have been done, just cross referencing here.

Any smoke or fumes at all? You haven't had the prop in bits by any chance? Wondered if it might be a phasing issue.

Chris

 

[Jon Wildsmith]

If it's doing it stood still then it's the pump or injectors. Sounds like the problem JB had when he had his pump rebuilt and had it done several times trying to fix it

 

[Jon Wildsmith]

See this thread, I know John had problems with it for a long time, don't know if he ever got to the bottom of it but it might give you some ideas.

 

[Gary Stockton]

Engine / cog-box / t-case mounts?? Simple stuff before hard stuff (I know, I know - BTDT). And disk rotor warped, maybe?? Any funny sounds associated with it, besides the driver cussing?

 

[Ecoman]

Just been out to check and it does it the same forward and reverse. Again it does it when its idling but becomes really pronounced when in gear. There is a wee bit of smoke but I have put that down to weeping valve stem seals. It has done 160K and probably ready to get them done but will live with it for a wee while longer.

Not had the propshafts apart at all but I'm ruling out that side of the transmission as it does it while stationary.

I have been having another think about this and was wondering if maybe it could be something like torque converter or fly wheel?

No obvious sounds from anywhere. To be honest its almost like the engine is missing a beat but sounds perfect. All mounts are fine as far as I can tell by checking with a long pry bar and a lot of grunting. Again does it when stationary so ruled discs out. Although they were all replaced earlier this year with 3G brakes and after the issue started.

Apart from this issue it runs fine and has oodles of power and is smooth as you like once moving.....Man I love this 80!

 

[Cptsideways]

If its an auto......


(away from obstacles in front) Stick it in gear, left foot on brake hard & it should/will rev to about 1500 rpm before the stall kicks in on the torque converter (it'll go forwards)

Does it do it then? If so you've ruled out your driveline if not it is in your driveline.

 

[Ecoman]

If it's doing it stood still then it's the pump or injectors. Sounds like the problem JB had when he had his pump rebuilt and had it done several times trying to fix it

Yeah I am assuming it may be something the specialist has done to the IP as it started the day I got it back from them. I took it straight back the same day and they kept it for another 3 days but it came back the same. The chap never drove the truck before hand so had nothing to compare it to so didn't know what it was like before. He stripped and rebuilt the pump for a second time but still no joy so put it down to a secondary issue like hydraulic lifters, valve clearances or something like out of balance flywheel or whatever. He thought it might have possibly been there before but since the injectors were in such a poor state that it masked the issue. I went along with his verdict and never had reason to doubt him as they have worked on my vehicles before and never had an issue. Although I'm beginning to wonder

 

[Ecoman]

If its an auto......


(away from obstacles in front) Stick it in gear, left foot on brake hard & it should/will rev to about 1500 rpm before the stall kicks in on the torque converter (it'll go forwards)

Does it do it then? If so you've ruled out your driveline if not it is in your driveline.

Right i just went out and tried this.

I pulled out of the drive and onto the road. Hard on the brakes into drive and put the foot down. The 80 stayed still and the engine revved to 2100 rpm and then wouldn't rev any higher. I did it a couple of times but same results every time. No vibration or shudder when revving or under load.

 

[Jon Wildsmith]

Long shot but check they adjusted the TPS cable from the IP to the gearbox correctly when they put the IP back on though I've never known one cause vibration at idle. With it in gear and doing its virbration thing, pull the cable a bit and see if it has any effect. It's by the throttle cable but it's not the throttle cable, heads off towards the transmission tunnel, controls pressure applied to the clutch plates in the box and not enough pressure causes judder but usually while you're under way so the fact you don't get any with your previous test makes it seem a long shot to me.

 

[adrianr]

Whats she ticking over at?

 

[Ecoman]

I will check the cable tomorrow Jon.

Its ticking over at around 800 rpm IIRC but again I will check tomorrow. We set it as per the manual but did try raising and lowering to try to eliminate the issue. If we raised it enough it revved passed the shudder.