300CE trans ideas - PeachParts Mercedes-Benz Forum

bkaiser · #1 04-30-2006, 01:28 AM

Hi All,

I have a 1993 300CE 3.2 auto that I love and intend to keep. I have had the car four years and purchased it with 120,000 miles. It now has 147,000 miles. I've been using Mobil 1 every 3-4000 miles and have changed the trans fluid twice. Both times the fluid looked good, didn't smell burnt and the pan was free of any tell-tale material. My dad owned an automatic transmission shop for 37 years and it is still in the family, so I have access to expert help and equipment. (sorry for the rambling)

The trans has always been fine, with the only hint of trouble being a real firm shift especially into 4th gear. This past winter (temps 0-30F) it started taking longer to go into gear when cold. It didn't slip, just took a couple seconds and then went in with a pretty good clunk. It also became very harsh shifting into 4th, to the point the rear end clunks when it shifts. It got better when warm. It was not harsh if I manually held it in 3rd and upshifted to 4th. It seamed worse under light throttle. I also have the feeling that unless you come to a complete stop, it doesn't downshift to first. When slowing almost to a stop and then accelerating, the car feels like it's in the wrong gear and then clunks and takes off.

Also the car has had an erratic idle since I've owned it, especially if you shut it off and start again. It wants to stall untill the idle stabilizer kicks in and it cycles through this untill it is shut off again. It also does it if you accelerate hard and then let off. The dealer replaced the mass air flow sensor and that seamed to help a little, then the problem returned. I put in new standard Bocsh plugs, wires and connectors and tracked down a few vacuum and air leaks like the throttle body boot. None of this realy made a difference.

I did a lot of searching and read Stu Ritter's article in the Star about lubricating the throttle linkage. My linkage had a lot of play, almost a quarter of an inch on the throttle cable guide. I lubed everything with Marvel Mystery Oil and experimented with the adjustment according to the factory M104 engine manual. This seamed to help a lot. The car had much better responce, seamed to shift better and idle better. The harsh 3-4th shift was better, but still very hard under light throttle. I felt I was in the ball park but still needed some help. The dealer kept it for a couple of days, but didn't help the shift much and screwed the idle up again.

After reading about the B2 piston and other problems, I decided to change the fluid again. In the past, I have used a whale oil suppliment that my dad swore by for freeing up sticking valve bodies that sometimes caused similar problems. This time I didn't. I put in four quarts initially and added another pint over the next couple of days. I don't know why, but changing the fluid softened the shift to the point that I thought I might hurt something, so I adjusted the cable up to get a firmer shift. At this point the shift was pretty good, and very good going into 4th, but the idle was still screwed up. The Mercedes tech mentioned that if the linkage isn't perfect, a micro switch in the electronic throttle body may not be trigered.

I took the throttle linkage apart off the car and cleaned everything. Even with lubricating, it was still very gummed up. I spent a lot of time and made sure everything worked smoothly. In the past I was never able to get rid of all the play an susppected the linkage was not returning to the throttle stop. With the linkage unhooked, the idle was perfect. It seemed like a spring should be pulling the linkage againt the stop on the throttle body. I don't know if it is supposed to have a return spring or not, but there is a hole in the bracket and a pin on the linkage arm that look like there shold have been a spring. I made one out of an old carburetor return spring that worked perfect. WOW! what a difference. it hasn't idled this smooth since I've owned it.

It shifts very good now. But transmission ghosts have got me spooked to the point that I'm afraid to drive it. A couple of weeks ago, I left work and hit a couple of traffic lights and everything was fine. At another light, I stepped on it and nothing! It felt just like neutral. I went through the gears a few times and then it took off like nothing was wrong. I wonder if it wasn't in gear all the way. after reading about adjusting it, you can feel that the detents in the trans don't line up to the shift gate exactly, but it's not far off. Since then I am very deliberate about making sure I feel the trans detents instead of just letting the lever hit the gate. It hasn't done the neutral thing again, but it feel like something is wrong when i put it in gear after sitting all day. You can feel the trans engage reverse and drive fine, but when you move away slowly in drive, the car moves a few feet but then clunks hard and the takes off. Almost like you were try to drive a standard off in 3rd. There is the sensation that there is about half a turn of play in the rear end before it clunks and takes off. Today i sat in the parking lot and experimented trying different gears and creeping away. The car actually creeps in neutral. I thought it was rolling a little but tried it in different places and it creeps in neutral. When it is warmed up it doesn't.

I odered a trans rebuild manual and am contemplating going through the trans. I thought about changing the B2 piston and installing the K1 spring kit first. I also want to replace the flex discs.

I'm sorry about this extremely long post, but hope somebody may find the linkage adjustment trial helpfull. I hope sombody has some thoughts about the trans. I would like to do Tri-a-rama this year but am afraid of the transmisson.

Thabks everybody in advace,

Bruce

skiier3_9 · #2 04-30-2006, 01:43 AM

I need to lubricate my linkage..my idle is just a bit rough (slight vibration at 550 rpms when the car is warm)

I'm hoping that this fixes it. Thanks for the information!!

BTW: Does your car have ASR? I've read a caution in the manual about moving the throttle linkage from under the hood causing the ASR to go into limp home mode. I'm assuming this is only with the car running.

pmally · #3 04-30-2006, 03:42 AM

its a diesel right? if it is it should be ideling around 800rpm... i think

haasman · #4 04-30-2006, 05:36 AM

Bruce

I am unsure about your transmission issues. Hopefully someone will be able to knowledgably reply.

I do appreciate your discussion and reminder of lubricating throttle linkages.

The wagon had a very annoying throttle transition problem: from idle to first application, the pedal seemed to stick. It was recommended that the throttle cable be replaced. After a lot of work and no change, I went about cleaning and then lubing the throttle linkage. What a difference.

Haasman

mmountainbiker · #5 04-30-2006, 08:10 AM

sometimes the transmission starts of in 2nd gear.If you move the gear selector to nuetral then back to drive it will start off in 1st.. This coupled to the clunk makes me think about the flex plate.

softconsult · #6 04-30-2006, 09:06 AM

I may have missed it in your post, but have you checked you shifter bushing.
Cheap part. After 150K miles mine had disintegrated. Common problem, but perhaps nothing to do with your particular issues.

Steve