B3 bi turbo shudder problem

[Timbo76]

Hi, new to the forums so any help appreciated. Just brought 2008 b3 bi turbo with 73k on the clock.. love it however a shudder is apparent like going over a cattle grid between 2-2.5 k revs between 25-40mph.. after reading some info is that it will be torque converter? I’ve changed all plugs and coil leads in case it was ignition but made no difference except it goes like a rocket 🚀 anybody else’s had this issue and or resolved it? It doesn’t do it cold and starts 15 minutes into a drive.. not tyres or unbalancing .. any help appreciated 😬

[ade and liz flint]

Prop shaft is my guess.

Does it do it more whilst coasting down through the revs than accelerating quickly through the revs?

Is it apparent in same engine rev range in all gears?

Is it always apparent at the same road speed irrespective of gear?

If you sit at say 30mph and manually change gears up and down, what happens?

[Timbo76]

Many thanks .. it only does it on acceleration and you can drive out of it with a little more gas. It’s really annoying and lets the car down.. gears all smooth and only does it at low speeds ..

[ade and liz flint]

Many thanks .. it only does it on acceleration and you can drive out of it with a little more gas. It’s really annoying and lets the car down.. gears all smooth and only does it at low speeds ..

See my little test routine above, added since you responded.

Revs, gears and speeds are important dictation of where problem may lie.

'more gas' means a change of speed. Need rev and gear info to focus in. A clear set of tests and answers may answer your problem.

Cheers

[Timbo76]

Appreciate it .. in answer to your questions

Does it do it more whilst coasting down through the revs than accelerating quickly through the revs? It does it more as the revs coast down and then you accelerate.

Is it apparent in same engine rev range in all gears? Yes 2-2.5k

Is it always apparent at the same road speed irrespective of gear? Yes anything from 25-40

If you sit at say 30mph and manually change gears up and down, what happens? It’s not as apparent but in fairness I still believe I can feel a slight shudder.

Rgds rich

[Timbo76]

I’m not getting any noises other than the shudder.. could it be the prop shaft bearing support?

[ade and liz flint]

http://www.realoem.com/bmw/enUS/showpar ... Id=26_0233

Items 7,8,9 are my guess already. See if you can get that inspected. At least if that's good, we look elsewhere. The tests I outlined help identify this, too.

I wouldn't expect much noise as it's low frequency. However, with vibration there is noise as it's one and the same. Guess who's a retired noise and vibration engineer?

[Timbo76]

😂👍🏼 many thanks for the info will try and get it up on some ramps first and have a look

[ade and liz flint]

Does it do it more whilst coasting down through the revs than accelerating quickly through the revs? It does it more as the revs coast down and then you accelerate.

Is it apparent in same engine rev range in all gears? Yes 2-2.5k

Is it always apparent at the same road speed irrespective of gear? Yes anything from 25-40

If you sit at say 30mph and manually change gears up and down, what happens? It’s not as apparent but in fairness I still believe I can feel a slight shudder.

Right, this still supports a propshaft bearing issue. The 1st test basically aiming my sights firmly there as acceleration through a resonance causes a narrow peak response, whilst deccellerating allows the response to show over a longer time period, and therefore feels 'worse' (and actually often is worse as it's underdamped by the load). There is also the effect of torque in the driveshaft which changes the response.

Your gear ratios are keeping the resonant response within the same engine speed band, and that will determine the road speed you feel the response at ie in lower gears it will be at lower road speed, higher gears a higher road speed. Try and see if that's what you're experiencing: if so, it's almost certainly the resonance of the unsupported propshaft ie the centre bearing isn't doing it's job of a) isolating and b) damping the vibration. It also means its third responsibility ie holding the propshaft in the correct alignment position is compromised and it may result in some wear in the shaft linkages, so try to test as stated and then get it in the air to assess that position.

[Oneball]

Noises are very subjective however it does sound remarkably similar to what I had with my E46 B3s, that turned out to be the lock up clutch in the torque converter, mine had done a similar mileage to yours at the time. I can recommend Auto Trans in Gloucester but that might be a bit far for you.

Find a auto transmission specialist and get them to have a drive. I took mine to Auto Trans, Doug drove it to the first island and diagnosed it straight away, when you know what you're looking for I guess it's obvious.

[Timbo76]

All many thanks for the comments and advice.. I got it looked at on the ramps today at my local garage who I trust.. the prop shaft and flex disc are in good condition and no movement,flex or wear. However there is a leak from the rear seal on the gearbox which is a plastic o ring inside or two.. mechanic states it’s probably this causing the issue as air and low fluid is causing the issue.. hopefully.. he will be fixing it with new filter and oil and seals so will update then. 👍🏼

[ade and liz flint]

Fingers crossed!

[Adwo]

All many thanks for the comments and advice.. I got it looked at on the ramps today at my local garage who I trust.. the prop shaft and flex disc are in good condition and no movement,flex or wear. However there is a leak from the rear seal on the gearbox which is a plastic o ring inside or two.. mechanic states it’s probably this causing the issue as air and low fluid is causing the issue.. hopefully.. he will be fixing it with new filter and oil and seals so will update then. 👍🏼

I take it you will have the gearbox flushed? Every 2nd oil inspection Alpina says to have the gearbox oil changed..

Cheers,

Adwo

[Timbo76]

Well just got the b3 back after being away all week and it’s has a new pan, filter, oil and mechatronic valve body which was leaking and glad to update that all is well and the shudder is gone! Smooth as silk now so more than likely low oil and leak didn’t help.. apparently these mechatronic valve bodies are very common to leak. So hopefully all fixed! Once again many thanks for all the help! Great forum

[ade and liz flint]

Pleased you're fixed! Although at some cost. Ouch!