Drive Train Backlash

[john_char]

Hi all,

I noticed on the way home today that the backlash in my drive train is getting worse.
My truck is an Auto and it happens as you back off the juice, let the car slow down then accelerate. I get a thump and off it goes. Does anyone have this?

I have checked my diff and there's no leaks out of any seals or anything out of the ordinary.

Thanx in advance.

John

[mr_grumble]

Worn Universal Joint ???

I get a CLUNK if I go from no juice to lotsa juice too quickly

[john_char]

I wouldn't think that my uni joint wouldn be worn, only done 140000, will have a look tomorrow.

[Muzza]

Hi John, have you tried the same with the auto locked in 1 gear ( manual mode), I know in auto mode the transmission can jump 2 gears
Muzza

[brett]

I don't think it's wear, mine's had a bit of a thump in it from new, not all the time but certainly as you describe when you back off and then accelerate it does it. Mines a manual and also notice it when changin gears. Never really looked into it, I thought it may be related to the LSD, or maybe just a inherint design problem.

Although I see you have an exceed so you will have TC and an open centre diff, so that counts out my LSD theory.

[john_char]

Thanx Muzz, I will try it out tomorrow. It doesn't seem to jump gears. It's just a thunk in the back of the car. Not too concerned, it's just a little annoying.

[psproule]

John, a lot of owners of 5 speed manual's complain of this. Indeed, ours was chronic @ 175,000km. The transmission / transfer was only 30,000km old, the rear drive shafts / CVs were only 23,000km old. So I put it down to a tired diff through a few K's of hard work and towing. Imagine my surprise when changing the companion shafts (for another fault - the leaky seal problem) that most of the backlash disapeared. The splines on the old companion shafts had worn considerably as had the bearing surfaces, allowing the shafts to float around a fair bit.

Try this - crawl underneath (dont jack it up) with the transmission in neutral but handbrake on. Grab the tailshaft and rotate as far as you can in either direction. Do you see the companion shafts move about either side of the diff? Mine not only rotated, but cocked sideways due to the slop in the bearings. The new shafts hardly moved at all, and the remaining play appeared to be in the diff crownwheel / pinion. You can actually measure the total backlash with this method although I cant tell you the maximum allowable as I do not have the manual with me. I can look it up from home if you wish.

Another potential culprit - a worn output shaft from the transmission into the transfer. I know of 2 auto NM's that have had the splines wear right off the shafts. They eventually let go with a bang, but I would imagine that they would have had considerable slop in the mating before they went. Indeed, the shaft on our old 5 speed manual was just about to let go and was the reason we swapped the whole transmission / transfer out.. I understand that it is only likely in ones that have had a heavy towing life, although having seen the rust around ours when dismantled I wonder if the location of the AC drain might not have assisted matters.

Pat

[6G74]

I cant believe you bought another pajero... its not like you had one or two problems, there were a handfull, a couple reoccouring. Once bittin, twice shy for me...

[gaz1]

Hi Pat

I've noticed a bit of backlash in my '02 NM auto recently, and will try to track it down before I go away again at end September. It is much more noticeable in 2WD rather than 4WD - to me, that tends to indicate the diff/companion shaft area being the most likely culprit. What do you think?

Gaz

[psproule]

Yeah - mine had less backlash in 4WD. If you follow the check I mentioned above.

6G74 - I know what you mean but I'll give you another saying - "Better the devil you know". It came down to price vs features vs performance vs on-road / off-road handling balance. 3 years of factory warranty left also helped.

It has been interesting carrying out the mods to this one. They actually changed quite a lot of small things from the NM to NP that I keep finding. The extra sound deadening being one, the carpets being a solid mould being another (hard to peal up to get at cable access trays). Despite our problems I still think these things are reasonably well built.

Pat

[john_char]

Pat,

I have also upgraded from the NM to NP, but to tell you the truth, I really haven't seen too much different difference between the two models, except for the cosmetic. A list would be cool, that's if you get the time.

John

[gaz1]

did the test today as per Pat's suggestion, everything seemed tight. Could barely move the tailshaft, probably only a few mm movement at the circumference and barely visible rotating movement in the companion shaft flange. No sideways cocking.

So I'm now considering whether the problem is paranoia on my part - maybe the apparent backlash is no different from what it's been all along. But I'll be keeping an eye on it just in case something else is causing it - hopefully not the output shaft from the transmission.

Also checked the front wheel bearings, no detectable movement/end play. This car has only done 111,000km so it's still relatively young in terms of distance, albeit quite a lot of that distance has been towing a van weighing in at 2300-2400kg.

Gaz