New Owner - Driveline vibration under load
Hi there - I live in New Zealand and recently acquired my 1992 300 GE 3 door with 83,000mls on the clock. This G is in near perfect condition apart from one or two issues:
The immediate problem is a driveline vibration under load.
When climbing a steep hill or accelerating heavily from a corner at low speeds and under normal suburban driving conditions there is a soft rumbling vibration in the car.
The vibration is quite subtle and most apparent to the driver - passengers often don’t notice it.
It phases in and out at about a one to two cycles a second – builds up then disappears over and over again until the power comes off. It's not revs dependant as the frequency stays the same if the car cuts down a gear.
The driveline and car is perfectly quiet when highway cruising with no vibration evident although I do fancy I can feel it on sweeping corners at highway speed.
My mechanic has repacked the front hubs, rotated the tyres, inspected the drive shafts and repacked the drive shaft sliding joint – all to no avail. He's stumped and doesn't want to consume more of my money without some fresh ideas. G’s were never officially imported into NZ so there’s not a lot of hands-on experience. Does anyone have any firm leads that could assist the mechanic to pinpoint the problem?
Many thanks,
Stu
Hello Stu,
If you have a CV joint on the prop. shaft between the gearbox and transfer box; the grease in the CV joint tends to harden and can cause vibrations. Strip down the CV, clean and repack with fresh grease.
There is an article covering the topic of vibrations on our 'home page'.
Check the engine mountings, transfer box mountings and in particular the front prop. shaft's front UJ.
Pack grease into the hubs does not lubricate the wheel bearings merely, acts as a reservoir to grease the swivels.
Note: excessive play in the front bearings would mean renewing the bearings. Do not attempt to readjust the wheel bearings, they will simply collapse after a short while.
After all joints have been checked and nothing is obvious, the transfer box itself can be the culprit.
Please give feed back on the article; if it was helpful or not.
turn the radio up
If the tyres have plenty of tread it might be worth having them inspected and rebalanced, otherwise perhaps an early replacement if they're due anyway. Check the wheels are not buckled at the same time. Is it a vibration you can hear, or one you can feel?
Sorry for slow reply, missed seeing your post. Great idea - my tyres are only about 70% worn but I would happily replace them if that solves the problem but could wheel issues produce a vibration that is; 1) load-dependent, and 2) that phases?
Load dependent - I have now noticed the vibration at other speeds but it is still most pronounced at 40/50kph when climbing a steep sealed road under heavy throttle. Last night, I could faintly detect it while coasting down a long section of down-hill motorway at about 80/100kph on trailing throttle. But, it rolls as quietly and smooth as silk when coasting over good tarseal with no load in either direction between wheels and motor.
Phasing - rather than just being a consistent smooth rumble , when it does appear it has a pronounced phasing, i.e. (and don't laugh): "...rrrRRRRRRrrr.....rrrRRRRRRRrrr...rrrRRRRRRRRrrr..." at about two cycles a second. It will stop immediately if I take my foot off, or when the suburban speed limit of 50kph is reach, which, I guess, is the same as lifting my foot up. I don't know if the phasing is significant or even helpful, but it's not what I have experienced in the past with an out-of-balance wheel's continual and even beat.
I still like the tyre idea as I can imagine poor casings fluttering under load (existing tyres are Hankook).
Worth a go, you think?
The fact that it happens under powert and increases with load pretty much rules out tyres, bearings etc.. Assuming its not something exotic gearbox, transfer case) then I think Rakesh is on the money - I'd bet it is main propshaft UJs worn. Changes under load because the angles on the joins change.
You should be able to tell if this is the case by getting under the truck and trying to move the UJs (laterally) relative to the fixed ends.
Fix is to have the shaft rebuilt (new joints), easy enough to do if you get someone like Propshaft services to do it (around £250 from memory) http://www.propshaft-services.co.uk/ They can arrange collection and delivery, turnaround in 3 days when they rebuilt my main shaft.
If you get anyone else to do it, make sure they can re-stake the joins, don't let them spot weld washers to hold them in place which is what lots of bodge-it-and-scarper outfits do.. New shafts are expensive - north of £1200 and providing the splines on your shaft aren't worn then with the joints replaced its as good as new.
LOL.. OK so I just spotted where you are... !
North or South Island? Married to a Kiwi (Taihape) - she's out there are the moment in fact.. 28 degrees she tells me :D
Anyway, propshafts services could do it, but the postage would be a killer... So you need to find someone who offers that same services.. if you get stuck for the replacement parts, then those would be postable and again Porshaft services would do this I'd guess (if you get really stuck PM me and I'll see what I can sort out for you).
Wow. Small world - Taihape on the main trunk line :) That's not far away, I'm in Tawa, just north of Wellington. She will be enjoying the warmth - we had 30c in Wellington on Christmas day. That's very warm for us, it's been a lovely summer.
My 463 has just turned 130k kms today, only 80,000 miles and has had an easy life.
Thanks so much for your help. I'm using a euro specialist workshop in Wellington called Motorworx - the mechanic there feels he's ruled out UJ's. That was actually how I initially described the problem to him - feels like worn UJ's. He's tested them, greased them and reckons they're OK. He commented that the UJ's have already been done because they have nipple points and the originals don't.
He's pumped grease into the sliding spline joints too, and regreased the front swivel joints. He's tested wheel bearings and everything else he can think of. He says that there was massive play in the front bearings and he's adjusted this out.
After reading the message from Rakesh, he now plans to strip the front drive shaft - and secondly, replace those front wheel bearings.
Maybe a silly question: is it possible to disconnect either the front and/or rear prop shafts and still drive (being permanent 4wd) - that would at least allow a conclusion over whether its front or rear? It really has to be to do with something twisting out of true when under load....
Thanks for your assistance!
Lol - just played that old song in my mind over again; it's 'Taumarunui on the main trunk line' - sorry, I'll have had you confused!
Yup, good old highway 1 :-)
Sounds like you've covered it quite well on the propshaft then. As a 463 its permanent 4wd obviously so I don't know whether the rear or front shaft experiences wear.
Massive play in the bearings and they definitely need to be replaced. Adjusting them is a very temporary solution and I think they are then prone to sudden failure.
If you disconnect the front propshaft I seem to remember there being an issue with the oil pump in the transfer box being driven by it... though now I think about it perhaps that is the 460 as I remember the advice being to put it into 4wd to overcome this.. others here will know for sure.
80K miles is not old - has the truck been used offroad much? How are MB for parts over there?
You might want to get a price up front from your mechanic for replacing the front wheel bearings, they are not easy on a G especially if he has not done them before.
I had a similar vibration/rumble in my 463 which was cured when I replaced the front wheel bearings.
Thanks again. Well, seems those wheel bearings must be swapped out! I've also learned a special socket is required so I have my fingers crossed that the garage has one of those, they're not likely to if the tool is G specific ... but probably will do if the socket is used on other Benz.
No - the truck has not been off-road prior to one careful expedition in my hands just a month or two back. I loved it offroad but hated the risk to paintwork. Even with its current 'AT' style tyres, it performed incredibly well. Approach and departure clearance is much better that I expected and when those diff locks are on - wow.
It’s been cossetted.
Thanks Bigblock! That's a positive message (apart from warning of high cost, that is). I will get a solid price indication.
But it is great news that having your bearing replaced cured a similar rumble. Do you recall if your rumble was like mine; a low frequency phasing rumble more strongly felt under drive-load?
The original propshafts have grease nipples, but you have to take out a plug, screw in the nipple, then remove it and replace the plug. Owners who do their own servicing replace the plugs with nipples and leave them there to make the job easier. It would seem as if this was done to yours, in which case it had an owner who cared.
It doesn't sound like a propshaft as you can usually a) feel it through the floor or steering. b) It's usually at higher speed 65 m.p.h. for about 5 m.p.h. and you can drive out of it, until the propshaft disintegrates, of course
With permanent four wheel drive, the only way you can drive it with one propshaft removed is to engage the centre diff lock.. If your front wheel bearings needed adjusting this sounds like a good place to start.
Hankooks are not my favourite tyre, but each to his own. Get the wheels spun on a balancing machine and visually check for any flutter, and also check for wear on the tread. I had some tyres wear the leading edge of the tread block down, so there was a distinct difference in height between the back of the preceding tread block and the front of the following one.
Best idea so far is the front wheel bearings. They shouldn't have needed adjusting.
Oops - missed an A to a Q; plenty of conventional MB's here, but very few G's. I doubt the national G population would get into three figures, probably closer to double digits.
Thanks FP - I will be getting the front wheel bearings replaced. To me, it still feels totally like a bad UJ but the mechanic has ruled that out. The mechanic also has a theory about a weakened axle or front shaft that was deforming under load - but he did say it was a long shot.
Your propshafts will have been balanced as part of the manufacture, they are balanced by welding weights onto them, thes can fall off, giving you a thrumming vibration through the body.
The speed of the input shaft and the propshaft is different 1.05:1 I think. the pulsing nature of your vibration means you have two shafts slightly out of balance, the pulse is when the two shafts go in and out of resonance.
Gordon
Hi
Front Hub Nut Socket is Part Number W460 589 00 07 00 and is the same for 460 and 463 and is used on some MB Commercial Vehicles as well but not as i recall on any Passenger Car models.
You should be able to get a standard version i would think and if not it would be very simple to manufacture as a one off if required
Gav
Thanks Gav, v.helpful - we should be able to nut that out by the sound of it (haha - excuse the pun).
Cheers,
Stu
Great - that's a new idea - thank's Gordon. I'll check for the weights (or spots that look like a weight is missing) asap.
I will update...
Cheers and thanks,
Stu
Hi all - an update. I have not yet managed to get my G booked in for the many suggestions you guys have offered me.
I had a second mechanic look at the G today. He immediately noticed that the knuckles of the two sets of UJ's on the front and rear driveshafts were out of alignment.
By removing the bolts from the diff-end flanges, it was easily possible to slide the ends of the tubes off the splined joints, and then reassemble with the knuckles aligned.
This has made a big difference, but not completely eliminated the issue. The power of the rumble waves (when driving uphill, in low gear and under heavy load) has greatly reduced, but is still there.
It seems driveshaft issues are central to the problem.
Question: in which direction should the sliding joints face? My rear driveshaft has the sliding joint on the diff end while the front has the joint o the transfercase end. Are these orientated correctly? Does it matter?
Many thanks,
Stu
OK – that was wrong! I have now learned about the alignment arrow adjacent the grease point on the driveshaft sleeve, and the corresponding arrow on the yoke.
Since that last post, I have removed both secondary shafts, realigned and refitted.
While doing this put-right job, I took the opportunity to run the G around the block and up the steep hill the produces the rumble, with the front shaft removed, and then the rear shift. To do this I had to turn the centre diff lock on, with that done it drove fine.
The finding: the rumble is there whether driving through only the front wheels or only the rear shaft. So, I guess that leaves the door open for a failing of UJ’s in the GB to TC shaft, or something more sinister further upstream.
Any ideas?
Many thanks,
Stu
Rakesh, I have the vehicle vibration problem as well - just put a new post today in the forum- the vibration only happens between (50 -80kmph) on the highway and then the vibrations drop down after 80 kmph! Even after greasing the 3 prop shafts the noise continued. On dismantling the prop shafts and rotating I observed a noise from prop shaft cross area between gear box and transfer box front UJ. Need to find a source from where I can buy the CV joint assly as replacing the whole prop shaft is an expensive proposition.
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Hi Rakesh - sorry for my slow acknowledgement of your suggestions, I didn’t get any email alerts and so assumed no one had commented on my SOS. I will check regularly now I know that's required.
Thanks very much for your guidance, I have emailed this information on to the mechanic who is on the case.
My G is a 1992 SWB 300GE - so I am guessing it has the driveline CV joint.
I will update you on this thread with progress.
Many thanks,
Stu