Front Diff Problems

[LittleBean]

We have a newly acquired Bongo with which we are having some problems, maybe you can help.

Whilst approaching 70mph on the motorway we had a growing resonant hum. It got louder and quieter on cycle of around 1 sec. It then turned into a high pitched whine - it was difficult to spot as it grew louder and I was unfamiliar as to how a Bongo might sound. After a while we got a pungent smell and eventually a puff of smoke at which point we pulled off the motorway.

The vehicle is under warranty and the dealer has been very good.

They replaced the front diff as this was damaged and sent us out again. The same thing happened within 50 miles. The garage then found a vibration on the front part of the prop shaft and has now replaced the relevant drive shaft, the front diff and the front part of the prop shaft.

The problem is, we have a young family (2 under5) and are concerned about reliability. The dealer has offered us an equivalient 2wd van as an alternative.

Do you have any advice on what to do - persevere with the existing van or go for the other 2wd van? Can such problems be effectively resolved or could they indicate that there is something else wrong? Could these problems have damaged the gearbox? Are there likely problems with the viscous coupling? Are 2wd vans inherrently more reliable? Any thoughts much appreciated.

Thanks

[missfixit70]

I went for a 2wd specifically for that reason - less to go wrong. I've never been in a situation where I think "I wish I had 4wd" & I've camped on some wet & muddy fields over the last year or so & still managed to pull a trailer out without a problem. If you feel like you're constantly listening out for it & haven't got the confidence in it, & the replacement vehicle is in as good condition & you are happy with the dealers response I'd say go for it personally

Welcome to the forum by the way

[You've Been Bongod]

hi LittleBean

welcome to bf
could you please put your area where you are from in your profile so people near you can help if ever needed

about your bongo
i have a 2 wd and have been on beaches and in mud with it and have not got stuck
so if the garage are offering you a 2wd and its in the same condition with roughly the same miles go for it i would say
plus the 2wd are better on fuel

good luck

[Mikey B]

Welcome Littlebean.

We had the same problem when we first bought the Bongo. We have a 4WD Bongo and the problem was due to different tyres fitted - snow tyres on the back, road tyres on the front therefore we had a different rolling radius betwwen the back and front wheels. We danaged the front diff and had to have it replaced also changed the tyres to thesame size rolling radius - no more probs.
Think the smell is the gearbox fluid (I might be wrong) overheating.

Hope this helps

[LittleBean]

Thanks for the advice. I relation to this last post.....

I trawled the forum for advice on diff problems and came across the rolling circumfernce thread and I didn't understand. I am no engineer, but the way this 4wd system works in my mind is.....

Front Diff provides output to the two front wheels allowing front near and front offside wheels to rotate at different speeds

Rear Diff provides output to the two rear wheels allowing rear near and rear offside wheels to rotate at different speeds

Viscous coupling at centre allows differential speed for front and rear wheels to such a point as the viscous coupling becomes more "solid" at which point you effectivle "lock" the differential - which is handy when trying to escape mud under either the front or rear wheels.

So I would assume that if the front and rear wheels had different rolling circumferences then the central viscous coupling would firm up and this would result in additional tyre wear and possible problems with the viscous coupling. I guess it could result in damage to the front or rear diff but I would have thought that this would be less likely.......

Our problem initially is manifested the seal on front diff failing. Does this fit with your issue?

Thanks again

[mikeonb4c]

I'd take the 2WD they are offering if it is a nice vehicle in other respects, as you've lost confidence in this one (I would have). Unless you REALLY need 4WD, the 2WD is perfectly fine and less to fret about. I'm very happy with mine. There has been one occasion (waterlogged field this Spring) when I realised how outclassed the 2WD is by the 4WD (I slithered, they didn't) but I still got out the field as I always carry Fiamma grip mats with me for insurance.

[dandywarhol]

Pretty much spot on with the theory LB - search again and you'll find a diagram courtesy of Demon AV in Russia - it explains how to check the VC. It's my gues your VC is gubbed (technical term)

I bought a 2WD for exactly the same reasons as the others - less to go wrong and have only been stuck once when I went too slowly into a deep muddy rut 4WD would have probably got me out.........

[scanner]

I went for a 2wd specifically for that reason - less to go wrong. I've never been in a situation where I think "I wish I had 4wd" & I've camped on some wet & muddy fields over the last year or so & still managed to pull a trailer out without a problem. If you feel like you're constantly listening out for it & haven't got the confidence in it, & the replacement vehicle is in as good condition & you are happy with the dealers response I'd say go for it personally

Welcome to the forum by the way

Welcome.

Exactly and ditto to this.

[parabat2]

Sometimes the fluid in the viscous coupler thickens up permanently, perhaps because the fluid overheats. If this happens, the front and rear wheels are essentially locked together without central diff. This causes "wind-up" which can destroy the front diff and the rear diff. (It did on mine!)

So I would suspect the viscous coupler.

If I was getting one now, I would probably go for a 2wd!