Thwaites dumper gearbox problem....

[farmer boy]

Hi all, This is my first post. I have a Thwaites dumper - not sure exactly which model, but..... it is 4wd, looks like it may carry about 2 ton, has a petter 2 cylinder engine (19 HP ish), starting handle, hydraulic tip,...... oh and its yellow!

The gearbox has recently started to make an awful noise in 1st and second gear (top gear is much quieter) - I checked the oil and found that there was none! (or very little).... anyway I filled it with fresh ep90 and the noise is just as bad and when under load (climbing an incline with a full load) the gears appear to slip - bit like a slipping clutch but accompanied by horrible noises!
I guess the gearbox bearings are goosed?

Has anyone removed a gearbox and replaced the bearings? Just wondering if it is a diy job for a reasonably competent person?
Would appreciate and advice or guidance.

ps replacement gearbox is over £600 which is more than it is worth! The bearing kit is about £50.

[martyn williams]

If I were you I would have a go at stripping it down and fit new bearings. Use a camera to record your strip down so you can refer to the photos if you are stuck.You will save money and have the satisfaction of doing the job yourself You could also post the photos on here Good luck.Just take your time and mark every thing us as you remove it.
Martyn

[Stormin]

If it's not actually the clutch that's slipping I don't think £50 of bearings is going to sort your problem. Expect to find knackered dog clutches, gears or layshaft. Best case scenario if the gear selector fork is badly worn or adjusted so it's not fully engaging the dog clutches on first and second, but it will still have badly worn the mating faces of the dogs and usually leads to the gear stick jumping completely out of gear.

[farmer boy]

Many thanks guys... looks like I will try and remove the gearbox today and see what sort of a mess it is in... you never know I may get lucky and new bearings may sort it. Failing that I will have to sell it for spares... pity really as it runs well apart from the gearbox problem.
Would still love to hear from anyone who has removed a gearbox - I have never stripped one down before so it will be an adventure!
I will take pics - may be useful to others.

[todd5]

have a go yourself. i'm not a mechanic but i fully restored my winget muir-hill model 2s dumper includiong a renewal of everything inside the gearbox - and it worked afterwards! some good advice has been offered, take photos etc, you may find its fitted with a newage 42M gearbox, if so an exploded drawing of all the bits are in a download on their website. if you cant find it, let me know and i'll burn you off a copy from my cd manual. johntodd@jptodd.co.uk, tel 01980 626039. hope it goes well.

[farmer boy]

Thanks John... I will let you know how I get on - just need to clean 20 years of grease and muck off it before I make a start... can't even see the bellhousing nuts! Power washer needed I think!

[martyn williams]

Give it a good clean out and check for chipped gear teeth,excessive play in the shafts.The lower gears and reverse will have more wear due to the fact the dumper would be used in those gears more.The dumpers I worked on were realy given some stick as they were hired out as self drive.Check for wear in the selectors.With a bit of luck you will not have to spend much money.They are not too bad to work on as they are smallish gearboxes that can be fixed fairly easily.
Martyn

[farmer boy]

Thanks Martyn, I have removed the gearbox now and there is a LOT of play in the front shaft - (the splined section that slides through the clutch). Also there is obvious wear on the large gear at the front. The rest of the bearings/gears seem fine. I am just trying to work out how to get at that front bearing - I think if I remove the clutch actuator and thrust bearing I may be able to get at it from inside the bell housing?
Do you know if the new bearings are a push fit or will I need to have them "pressed" in? I will take some pics and post them asap.

[essexpete]

If the rest of the dumper is really straight and engine OK then you might pick up a box from a breaker. Most likely bearing wear due to the lack of oil, they also get water contamination when outside for years. As one post has pointed out the damage may already be done to gears and shafts.

[farmer boy]

I have stripped it and it appears that the problem is the shaft at the front of the gearbox (the splined one that sides through the clutch). The bearing you can see in the pics is VERY worn and this seems to have caused considerable wear on the gear teeth (see pics).
Can I get a complete shaft to replace it?

Maybe the bearing and gear need to be removed from the shaft? If so how will I do it? I have tried to drift it off but it will not budge - I am not even sure which way it would come off! I will also need a gasket set. Any ideas where I can get spares from? The rest of the gearbox seems fine with no play so I hope that will be ok.

There also appears to have been a bush between this shaft and its "mate" in the gearbox - you can see the remnants of it in the pics below (IMG_1193)
The gearbox came out very easily - dirty job but easy once the footplate was removed. The gearbox bearing is showing evidence of rust so I guess water has been getting in... oil was a horrible brown colour as well.... must keep it inside in future!

Hope you can help.

IMG_1196.jpg