There's a quick bust of moment when I engage overdrive.


Curious if others vehicles engage seamlessly or if there is any noise as well??


I've also noticed this nosie on the freeway when I try to get out of overdrive. overdrive well stay on and this vibration keeps happening until I put it in say 3rd and rev it up or stay in neutral. I'll have to mess with it to get it to stop....

a friend was in my car yesterday and mentioned that he thought it was a center support bearing. cause it was vibration on hard acceleration which I never really noticed so much. It did sound like it was coming from under the car.

a center support bearing is new to me, how it works and it's purpose, so I'm not really familiar with the symtops of one going bad.

 

Yeah, it does sound like a CB. To get the M46 to seamlessly shift into and out of OD, gently press on the clutch an inch or so past the friction point. Will shift much easier.

 

I'm thinking the next time I have it on the lift I'll see if I can get a hold of the bearing and feel for any play or roughness. I've done every thing else to this dam car, why wouldn't this bearing be out too.



I'll try pushing in the clutch next time.

 

ok so I've been pushing in the clutch before engaging OD and the engagment is smother. which is great. though the car will still shutter vibrate like it's still in OD after long segments of being in overdrive when I down shift or put the car in netrual.

I was looking through the owners manual ( which has a lot of great info and how things work, etc.) and it doesn't say anything about disengaging the clutch before pressing the od button, but it does say in bold to press the button manually disengaging from 4th before going into neutral. which I think makes it now vibrate so much. it's so hard to remember to do this everytime though, and I forget and it's hard to say if this alone is the cause.

I need to do one run to work where I exclusively remember to do this so I can rule this out or not.


as far as the CSB it's so hard to say if that thing is bad without it whining, which it's not doing, or taking it out and feeling it. I'm at the point where I've put a lot of money into the car and I don't want to replace anything else that isn't bad or needed.

 

The vibrating just sounds weird. I've never had that on my car. You could drain and refill the OD fluid, but I'm not talking from experience.

 

the overdrive is integral with the AW70/71 tranny, uses the same fluid. <== ignore this, I just realized OP said 'manual'.

here's a drawing of the driveshaft off a 240, the 700/900 is almost identical, but this is a better drawing showing the whole thing.


and here's the exploded drawing of a 740/940 driveshaft...



(click on those for bigger drawings...)

note the bearing is held in some rubber bushings, and those bushings can be shot, allowing the bearing to 'buck'. this can cause shudders. failed bearings themselves are more likely to squeal or scrape. ditto, bad U-joints can cause funny things. its usually pretty easy to see whats funky when the car is on a lift and in neutral, spin the rear wheels to turn the driveshaft, grab it and vigorously try and wiggle it up/down, etc.

belated update, the rubber bushings I mention are parts 4 and 5 in the 2nd pic. the bearing itself is 3. 2 is the cage that holds it together, and is bolted to a structural crossbeam. the bearing is pressed onto the front shaft 12, not something you can diassemble with hand tools. there's also two versions of this whole driveshaft assembly on 700/900's, Type 03 and 13, they different somewhat in the length of the two shafts (the inset drawing shows the bearing-to-end measurement for type 03, on type 13, the equivalent measurement is 208mm).

 

I drained and filled the tranny twice, because of a leaking OD solenoid. I thought the OD and tranny shared the same fluid?? I didn't see any drain for the OD unit.......?

 

I thought they are separate, but I've never changed it. Maybe they are the same. I would be a good idea to drop to OD pan and clean it. I think there's a magnet in the bottom. Then refill and check and top off after running it.

 

There's not exactly a pan. there's like a cooler and I believe a bunch of seals/rebuild kit.
You fill the tranny with ATF which makes me pretty sure it's the same. I'll have to look into it.

 

I've had the car in the air and didn't notice anything that really stood out. I didn't stare at the rubber. I'll have to look at it again. thanks for the pics.

disengaging OD before downshifting has been making a quite a difference......

There's this TSB where they want you to move the mounting of the bearing holder to decrease vibration on heavy acceleration......... it's really not that bad on accel though.

 

on the exploded diagram of the type P OD I looked at, there was a small rectangular filter and cover on the bottom of the OD

ok, you asked for it. one exploded P type OD as used on a 92 740T with a M46. I assume the earlier ones are similar... I do note there are two different P/N's for these, didn't bother to drill down and figure out the differences. The filter is #32, the cover is #30 plus the pile of gaskets and such around it.


(click for bigger)

hey, on the *other* diagram I'm not going to upload, there's a block under the back of it labeled 'oscillation damper'. looks to be some kinda rubber tranny mount. ya don't suppose THAT is your problem ?

 

I did replace the tranny mount ( a while ago when I first got the car).

I'm sure I would beneift from changing that filter and magnet. I'll have to see if I can those parts.

Are you getting these pics from vadis?

 

yeah. my russian bootleg 2005 vadis