New to me 300CD - Transmission Woes
 

Just got my hands on a '84 300CD.. thanks CDN.

Has an interesting transmission problem.

About 78 miles into my 180 mile trip home the transmission started acting up. Cruising along at 70mph and suddenly the RPM's hit redline. I backed of the accelerator and re-applied and the same thing free-spinning. Shifted into neutral and back into into drive, no dice, still free-spinning. So I pulled over and stopped. Left the car running and shifted to park, then back into drive and the transmission engaged. However, now it wouldn't shift.. stuck in 2nd gear, top speed about 35mph at 4,000 rpm. So I pulled over again and shut down. Let the car sit for 10 minutes tops. Started back up and drive off. Now its shifting all the way to 3rd gear, but not past 3rd. Eventually it slips again and won't enage.

Gave up had the car towed home. Incidently this started after I pulled off and refueled. Literally 2 miles after I got back on the road is when it started.

Any thoughts?

Try some Trans-X...... know trans fluid capacity before going to store, read instructions on can before leaving store, may need two cans....

The transmission fluid is full isn't it? Check it with the motor running and after a short drive to ensure it is warm. If it is overfull it will have bubbles in it and will probably free rev under load (only happened to me once backing up the hill in front of my house after fluid change), if underfilled it will allow the car to free rev.

To be honest its dark its raining and I have no overhead cover so I don't know. Thats my first suspect. I'll take a gander at it tomorrow when I get off work.

My thought was low ATF level.. its getting hot and turning to foam.

When ATF gets to hot it oxidizes and fails to do its job right, however when overfilled it will foam. The tranny fluid is probably the most sensitive fluid in the car. The level changes with temperature as the components expand and such. The defenition of warm for tranny fluid is after driving 10-15 miles, so this is when it should be checked for a detail check. To actually see why it is slipping or not just a little warm will give you an idea.

Re: New to me 300CD - Transmission Woes
 

Congratulations on your newest ride, James! When I saw the location in the ad, I thought of your hankering for a CD.

Sorry to hear about the non-optimal trip home, but hey, you've got the car, and you'll work it out.

Of course, I have my own self-interest working here, too. You know I'm looking, and with each car you buy, I figure you're that much closer to saturation. ;)

I think my wife will kill me if I bring another one home. Starting to look like a '80's Mercedes lot here in my driveway. Besides I have nowhere else to park.

You can gauge the ATF level cold if you are concerned about driving 10-15 minutes right now. Stone cold the level of a full tranny should show about 10mm lower than the MIN line on the dipstick. Anything lower than 10mm below the MIN and you are low, anything higher and you are likely overfilled. If you fall right baout the 10mm low mark then you should be good to go for a short drive to warm things up for an accurate read.

Well its definitely overfull. I drove it for about 10 miles stop and go with some cruising around 60 mixed in. Pulled over and checked the fluid. Didn't have a measuring instrument on me, however, the fluid was at least as much over the full line as the distance from fill to full.

I guess the question is, is that amount likely to cause the flaring I am experiencing?

Most likely. I'd drain it out ASAP! Having the fluid overfull is quite possibly worse than not having any fluid at all.

Well I suppose I'll take this opportunity to go ahead and drop the pan and change the filter out as well. I'm amazed at how much quicker off the line this thing is than my 300D. Guess thats what happens when you cut 500lbs off.

Wow I didn't realize the CDs were that much lighter.

Well I was going by the title which admitedly could be way off.

My '84 300D weighs in at 3900 lbs.
The '84 300CD weighs in at 3400 lbs.


After looking however...http://home.hiwaay.net/~gbf/mbmodels.html
Lists the 300D at 3515 and the 300CD at 3495. It sure as heck feels much lighter ;)

Ironically I still haven't had a chance to drop the pan. I'm actually going to do it as soon as I change cloths.

I took her out today for a nice trip. Went about 40 miles without incident. I stopped to use the bathroom and boom. Well more like.. WWWWAAAAAAAAA. Transmission now slips. If I manage to get it into 3rd or 4th it won't stay there eventually it will drop back to 2nd. Ironically 1->2 is still jarring, enough so that if I don't catch it in the shift and get off the accelerator, it'll chirp the tires.

One other thing of note. When its cold it shifts from 2->3 almost immediately after hitting 2nd.

I'm almost positive its temperature related. Could it be something as simple as overheating? My trans cooler plugged up? If so how would I go about checking that?

Not uncommon, don't ask me why it does this as of yet, probibly valve body related, there are updated service replacements for such issues with these trannys. Mine does this to a lesser degree than yours, I just add marginaly more throttle just after it shifts to 2nd, same with 3rd to delay the 4th shift a little. If you try and adjust it with the bowden cable to hold shifts higher you end up tacking really high at light throttle, which is anoying.

I hate these trannys.
But I love the engine.