Replacement differential

[Tilly]

The Rear differential is now really beginning to wine ( 79000 miles).

Recommendation is to get it rectified before it could fail. However, which is the best route to take.

BMW reconditioned exchange unit would be about £1700 plus VAT plus fitting.

A quote from a Gearbox/transmission specialist to replace worn parts for about £1000 plus about 2 hours labour charges for fitting. They would need to drive the car first but are confident they can repair the unit. The group have a good reputation so I am confident they could do the job.

Any suggestions would be appreciated.

[Ballie]

I have to admit; I dont think I have ever heard of anyone having to replace their Diff at 80k miles. Strange

[Deano1712]

Think you are better buying a secondhand diff and fitting that. They seem to hold up well so you should be able to get a decent one for a few hundred. Ebay is your friend.

[Tilly]

Thanks for the suggestions fellas.

I have to admit that 80,000 miles is a low mileage for this type of problem, especially since in my ownership it has never been abused and the car serviced as recommended.

The only thing I can think of is the car was a German prelaunch demonstrator, built over two months before the official press launch in Munich. Before the time I got it, although well maintained by BMW, I would imagine the car would have been subjected to some hard usage.

[Ian Kelly]

I'll second Ebay - there's a few on there for around £200-£400.

Swapping isn't a massive job, an Indy should only charge 2 hours labour (or you can scuff your own knuckles!).

Ian

[Dr Shiny]

I had just that job done on my 2.8 a few months ago.

A very, very noisy rear diff was replaced by a second hand one by my local garage.

It cost me a lot of money but a lot less than my local BMW dealer would have charged.

Paul

[Tilly]

The differential noise really became quite deafening. Could even now hear it with the top down. A whine starting around 40M.P.H. and getting louder and higher as the speed progressed. The car has just had a full inspection 11 service including a new vanos from a main dealer, don't ask the cost, but I really couldn't drive it in this condition. They did mention the noise in the service report but did not specify a likely cause. Further investigation required. The whine rapidly became worse over a few weeks. With 132000 Km on the clock I knew that transmission problems could soon rear their ugly head.

The engineers at a local specialist transmission company have now stripped down the diff. The good news is the gears are in good condition. However, the pinion bearings are failing. Bearings and seals they can get, gears are a different matter. Driveshaft and prop bearings are fine.

So new pinion and side bearings plus new seals are being fitted. In addition a braided clutch hose will replace the original part. Apparently a couple of the bolts on the diff had also sheared off, how that happened I have no idea. They believe they have found a company who can supply new bolts. I do not know which bolts they are talking about but when I collect the car I hope to get more details. The estimated cost of the work. The hose was £25 and its fitting plus the servicing of the diff about another £650.

Now just some new tyres and I hope that I can have a few months relatively cheap motoring.

[offyourmarks]

Tilly

Its good to hear you are getting things sorted.

Why did you have to have a new Vanos fitted just out of interest?

[Tilly]

Tilly

Why did you have to have a new Vanos fitted just out of interest?

Funny you asked that question today. Just returned from the garage since the estate was telling me Airbags failed and battery needs replacing. First was not a fault they could find and the second needs a programme update. They will collect the car in a coup[le of days time since reprogramming can take several hours.

While I was in the garage they gave me part of the old vanos. On of the gearbox outlet or input shaft the end had sheared off. I have the part and the shaft had completely sheered. Half of the vanos was not working and this was causing the poor pickup with a warm engine. The new unit totally cured the problem.

[offyourmarks]

Excellent stuff (If you know what I mean )

[Tilly]

Car back,

New bearings and seals have totally curred the rear-end noise. After an extensive road test the specialist engineer said that all the other shaft bearings do not appear to be warn and although there is a slight noise from the gearbox it is only very minor. With just over 130,000Km on the clock that is to be expected. However, if it gradually progresses it would not be a problem to strip the gearbox and replace any worn parts.

New bolts fitted to the diff. Mechanic said if the other two remaining bolts had failed I would have said goodbye to the diff; it would just have disintergrated. No idea how or why they sheared. While work was being done a new braided master/slave cylinder hose fitted. This has completely curred the stiff gearchange when warm. Car now once again a pleasure to drive.

Total cost of this work £798. Could have been a lot worse.

[Robert T]

Glad you have your car back and in good order, Tilly. I recently had a similar job done on the diff on my Frogeye, and it is much quieter now also - means I get to listen to the exhaust note rather than transmission noise. I'd be interested to know precisely which bolts had sheared - I had actually bought a complete replacement diff for the frog, but I took it back because the bolts that hold the crown gear wheel to the central hub (?) were too short - they were only about a third of the way into the crown gear and the rest was bare threads! If they went, it would make a nasty mess. Assuming that the zed diff is structured similarly, then could it be these bolts? Anyway, we replaced the bearings in my existing diff, for considerably less than the price of a replacement diff.

Cheers R.