Vibration under hard acceleration.

[Rtaylor2208]

Well it seems the cabby is having a bit of a hissy fit at the moment. Fixed the overheating and now it's developed a vibration under hard acceleration.

It feels like its comming from either the middle or rear.

The cab is a 325 switchable slush box if that makes any difference.

Any suggestions on the most common causes? I was thinking diff bush or prop centre bearing / doughnut

I've never inspected or replaced either so open to suggestions.

[Barx325i]

that's almost defiintely the centre prop bearing - the diapragm fails and it flails - it will just get worse and worse, but you can manage by avoiding certain torque levels and revs etc. Fairly easy job..

[rich318i]

that be the first things to check what you said.

[Rtaylor2208]

Is it easy enough on axel stands? Also do you know what parts I need and any tips on how to replace it?

[Barx325i]

depends how well you know your onions, but do-able with axle stands.. exhaust and heatshield need to come off, make sure you mark the prop before removing the rear section. There's a big circlip which holds the bearing in place IIRC

[rich318i]

nope needs to be up in the air to many things in the way like the exhaust, about an hours work

[Rtaylor2208]

It's a 2 piece exhaust so would that be front and rear sections? I'm no mechanic but have tackled replacing the shocks and springs, replacing the rear exhaust section, timing belt, and general service stuff.

A little wary of doing something and ending up with an undrivable car if I get well and truly stuck.

[rich318i]

it just more easy having it up in the air mate . and mark a line on the prop (both parts) so it lines backup or they could become unbalanced

[Barx325i]

If it's your daily then I'd say it's a £70 labour job, but I'd say just get stuck in - this is coming from a man who swapped a diff in a layby so depends how much you trust your own ability - have faith & logic applies - any issues, post back..

[rich318i]

^ bet that was fun lol

[Barx325i]

^ bet that was fun lol

no it was a cnut, and just about finished as the sun came up.. All character building stuff. I had a gopher, it's not like I carry a spare diff

[rich318i]

^ bet that was fun lol

no it was a ****, and just about finished as the sun came up.. All character building stuff. I had a gopher, it's not like I carry a spare diff

just a spare E30 on a trailer just incase lol

[Rtaylor2208]

The cabs just a sunny day toy fortunately so if it takes me a few hours or a few days it's not an issue.

Looks like I'll give it a bash myself. I take it I only need a new centre bearing and no other parts. Also any specific tools other than the usual sockets and spanners?

[rich318i]

dounut maybe awell while your there. no special tools needed just tipx for the prop marking

[Barx325i]

^ bet that was fun lol

no it was a ****, and just about finished as the sun came up.. All character building stuff. I had a gopher, it's not like I carry a spare diff

just a spare E30 on a trailer just incase lol

it went boom prematurely, but I'd sourced a replacement in anticipation, so we walked 7 miles at 11pm, picked up the replacement, drove back in my passengers car armed with torches and tools.. Summoned the force and a few hours later we were on our way..

sadly, the car STANK of diff oil for weeks after..

@ RT, get stuck in...........

[rich318i]

no it was a ****, and just about finished as the sun came up.. All character building stuff. I had a gopher, it's not like I carry a spare diff

just a spare E30 on a trailer just incase lol

it went boom prematurely, but I'd sourced a replacement in anticipation, so we walked 7 miles at 11pm, picked up the replacement, drove back in my passengers car armed with torches and tools.. Summoned the force and a few hours later we were on our way..

sadly, the car STANK of diff oil for weeks after..

@ RT, get stuck in...........

why did it go bang. did you find out?

[Barx325i]

Rich, the planetaries failed on the overun, over a particularly familiar and heavy undulation (see welded diff thread ) however luckily I'd sourced said replacement 2 days previously due to worrying clunking in a carpark.

RT, there's an important CPB preload to be aware of which means you install the prop as stated and set the CPB at rest, you need to push/preload the diapragm approx 5mm toward the gearbox.

[Rtaylor2208]

Barx i have to say that is Greek to me, but once I can get under the car and see what I'm doing I'll post back with more questions

[rich318i]

once your under there you'll work it out.

[Barx325i]

It decided that the load between competetive points of the diff internals were too much for it to deal with given the torque differences across the axial load of opposing rotational forces..

BOOM...


RT, when you re-assemble and slide the new prop bearing in place all is normal - when you come to tighten it up against the shell you need to push the bearing assembly, forcing against the diaphragm tension, towards the gearbox by aboiut 5mm before tightening it up..

[Rtaylor2208]

PM'd meatballs82 for the parts.

The tax is up at the end of September and realistically I'll do maybe 200 to 300 miles at the most before then. Is this a job that can wait till then or will any other damage be caused if I leave it for now?

[rich318i]

take it to kwickfit for a free brake check just tell them you think you need new brakes. its pulling to one side or something. while its up in the air check everything yourself. they'll say this is wrong and that to get you to buy new discs blarr blarr blarrr

[Barx325i]

remove exhaust
remove heatsheild
mark prop at the central join
detatch prop from diff
remove bust centre prop bearing (CPB)
refit god CPB
align prop
preload (force the bearing and rubber diaphram assembly against its will, about 5mm toward the gearbox and screw back up to the chassis.

refit the rest....

[Rtaylor2208]

Thanks that doesn't sound anywhere near as scary as I thought.

[e30-EVN]

nope needs to be up in the air to many things in the way like the exhaust, about an hours work

gotta be kiddin me..?... it can be done with axle stands and a jack. if i can do my whole m52 conversion using axle stands and jack then a prop centre bearing is nothing more than a minor inconvenience

[e30-EVN]

a vibration from the rear of my car under heavy acceleration in my case turns out to be the dif bush being mullered by the might of my right foot, or more to the point, a combo of that and the m52...

just incase the centre bearing doesnt cure it