lately, I've been having some strange small issue with the auto trans in my '90 240DL. it seems to stall/not engage when rolling slow then accelerating, or sometimes accelerating from a stop. like rolling into a slow right-hand turn, when I go to give it gas again, it's like the trans will have troubles finding the right gear. sometimes it seems to down**** too far and then shift again right away.

I've also noticed that when sitting parked and I put the car in reverse, I can hear something that sounds sort of like metal lightly clanging around...almost like change in a dryer. it's soft, and it doesn't seem to increase when I use the gas, but I haven't really given it lots of gas either. I can pretty much only hearit when I'm in the parking lot at work and backing out of my space. I can hear the sound reflecting off the cars next to me...if I'm out in the open, I can't hear it. shift into neutral, nothing. shift in to any forward gears, nothing.

now, I've not had the chance to check on the fluid...but I've not changed it since I've owned it (a little over a year), so that might be the first thing to do. but are there any other suggestions? anything outside of the tranny that could cause this?

J.

 

Shift linkage

a few bolts and clips on the shift mechanism.....

Pop the shifter cover off and take a look at the safety neutral switch...Triangle plastic thing with two screws holding it....look at the screws if missing or came off or what...you can tell when you go through gears if the switch moves and screwing with your gear selection. The noises are probably from the link mechanism loose or about to come undone....crawl under the driver side and use a flashlight to see if you notice loose parts...etc..have a friend shift (engine off) and see how all the parts move...

WHILE UNDER THERE....look at the "transmission mount"....it might be deteriorated and transmission is miss aligned. .....

change the fluid.......not hard at all....will take you about 35 minutes to replace.

 

are you talking about an auto trans? because that's what I have. sorry if that wasn't clear...

J.

 

Yes, I am referring to an auto transmission.

check out the picture I have included...look at the cables/links etc on the of an automatic transmission. yours might be a little different but just check for loose or missing nuts..etc...

check your transmission fluid level...and replace if necessary....we can give you a quick write up on how....not hard at all.

 

ok, thanks. that makes sense now that I see it.

J.

 

ok, so I drained the pan and put in more fluid (the old was really old looking and burnt, but no junk in it...) and threw in a bottle of trans-fix stuff. not stop-leak, but the stuff for fixing seals & whatnot.

anyways, checked the levels and they seemed fine. drove to work the next day and everything seems ok. the sound in reverse is gone, and it's shifting a little better. later on, I checked the level again (cold) and it showed that it was over the full line. not sure how that happened since it was fine when I first put the stuff in...

today, I go to work and my overdrive won't work. it's just off...hitting the button turns the light on in the dash, but the OD doesn't change.

was that something I did? I know that the OD switch is just something that happens to almost everyone, but I want to know if I messed it up somehow.

J.

 

you ALWAYS check transmission fluid levels with the engine running, and preferably with hte tranny fully warmed up (which takes longer than engine warmup, I generally go for a 5 or 10 mile drive at highway speeds, leave the engine idling, and check it).

critical to clean off the outside of the dipstick and tube before pulling it, as you don't want any grit to get in there.

just dumping your ATF out the drain plug only changes about half of it, the other half is stuck in the torque converter. you really need to disconnect the upper tranny cooler line at the radiator, connect a plastic hose into a measured jug, start the engine, and for each quart that comes out, add a quart of fresh ATF via a transmission funnel into the dipstick tube, until the stuff coming out is clear red. engine off, replace the cooler line, test drive to warm up the new fluid, check level and top off if needed.
see Transmission. Automatic AW70 and ZF

also you should check the slack of the transmission throttle control cable (often called 'kickdown cable').
see Transmission. Automatic AW70 and ZF

p.s. you undoubtedly have an AW70 transmission in a 1990 240 automatic.

 

so if you bump the kickdown cable it will kill the OD? I know I didn't mess with it that much, if at all. it would have been my hand touching it a little to get the funnel in the dipstick tube...

J.

 

bumping hte kickdown cable shouldn't matter, but if its routed wrong, or hung up on something, or there isn't the correct amount of slack as adjusted per that link, that will definitely mess with the shift points. if the cable is too tight, it will stay in a low gear too long and not upshift to a taller one, while if the cable is too loose, it will upshift too soon and not downshift, and the transmission is more likely to slip (and damage itself).

 

well, it shifted perfectly fine before I added the fluid. and adding the fluid is all I did. I thi k I'll check the relay and see if that's the issue.

J.

 

huh, you opened this thread saying.....

 

haha. what I was trying to say was that those issues were only when leaving from a stop. never on the highway or during normal driving. it shifted just fine under normal circumstances. sorry if that was confusing. I suspect those issues were mostly because I WS low on ATF. when I checked it after posting, the dipstick was almost dry. after putting fluid in, it shifted great for one day. then the OD went out.

J.

 

its possible that stop-leak stuff gummed up the OD mechanism, but just as likely that it was time for it to go.

so, you say the button toggles the light, but it never shifts into 4th? could be the wire to the OD solenoid, or it could be the solenoid it self got stuck. the relay is working because the light is toggling. note that the solenoid is powered the opposite of the light, if the light is ON, the solenoid is OFF< and if the light is OFF< the solenoid is ON.

you can fix it by dremelling a notch into the face of the solenoid, this will leave your OD permanently enabled, ignoring the button (I'd probably pull the relay so the light would stay off).

here's a modified solenoid, note the notch cut, and that the smaller o-ring is left out.




IPD sells a plate you can replace the solenoid with that does the same thing.

 

ok, so where do I find the solenoid?

also, how fast is too fast to drive w/out OD? I've been taking the back roads to work and never get above 50 or so on those. keeping off the interstate until I figure this out.

J.

 

nevermind...I found a PDF on IPD showing where it is. I'll check it out and see what I find.

J.

 

um, 3rd is good right up to about 100MPH which is pretty close to the top speed of a non-turbo 240/740/940. the engine will be revving higher than you might like, but its still under redline.

the OD solenoid is on the left side of the transmission.

 

ok, good to know. thanks Pierce.

J.

 

p.s. its virtually impossible to overrev a redbrick engine, as they have a rev limiter that cuts off fuel if the RPMs go too high. about the only way you could get past that would be downshifting at very high RPMs with a manual transmission (the AW7x automatics likely would refuse to downshift at too high of an RPM).

 

"Up to a 100MPH" in 3rd?
Oh, I don't think so!
It may not be redlining but I certainly wouldn't be trying that in a 25yr old 240 with tranny issues; may be 60MPH.

 

well, I got under the car on Sunday and found the wiring to the solenoid was corroded and falling apart. so I pulled it, dremeled it, and reinstalled. just like new!

thanks for the help guys.

J.