Vacuum / Shifting problem ??
 

Hello All. This is my very first post, but I've been lurking for years obtaining information to fix my baby.

This time, I need help, it's not a DIM (Do It Myself-er) it seems :(.

I normally do not drive her in the NY winter, but rather parked it in the garage. Last spring when I revived her, I had this new issue to deal with, and still haven't fixed it. Mind you it worked fine the previous summer.

The issue is with the transmission, I believe most likely vacuum related.
When I come to a stop or sometimes even just when coasting, it seems to act like it goes into neutral! When I press the gas pedal, the engine revs but acts like it's not in gear! Eventually it grabs and then off we go. This happens in every gear.

Also, it sometimes acts like it wont shift up, and doesn't seem consistent with any gear-to-gear shift, it can happen at any shift, and it actually just starts to gallop like a horse, as I say.

I think it's probably vacuum related because some days, it acts perfectly fine. During these sessions, it shifts like a dream, no missing or slipping feelings, nice and smooth. Unfortunately, these days a very slim to none.

I've looked at tons of vacuum and transmission threads, but I'm just not comfortable with any of it. I don't know where to start.

I really need help, I feel like I'm ruining my otherwise excellent car, simply because I can't afford to take it somewhere, and don't know what to do myself.

Thank you in advance!

Jared

On these MB's, a vacuum issue usually goes along with harsh shifting. Flaring is usually fluid related. When was the last fluid/filter change? When you check the fluid, it should be bright red and smell like sewing machine oil (ok I'm showing my age) without any burnt smell.

The first thing is to check the fluid level. It should be warm (20 min. drive,running in park, level ground) Don't overfill. I don't know about others but I've noticed mine is real finicky about the fluid level and should only be filled to the bottom full mark.

Hi Sam,

Thanks for the prompt reply! I wasn't expecting assistance so soon.
I checked it out, and you were right. Apparently I have a leak somewhere because it was at least a quart low.

Are there certain points that are prone to springing ATF leaks that should check first?

Hose the trans. off real good everywhere underneath. Top it off, go for a ride and put it on ramps after about a 20 minute ride. Crawl up underneath and see what you got. It could literally be coming from anywhere. Tail shaft, pump seal, converter drain plug, B2 o-rings, trans. pan drain plug, trans. pan gasket, etc....

Ok, sounds good. That was my plan if there were no spots that "always" spring a leak on these. Thanks for the help!

A couple of leak sources that I've run across besides the pan gasket:
Hard cooler lines.......the rubber in the clamps deteriates and result in metal-to-metal contact. Vibration causes the line to eventually wear through. (~$50 per hard line)
Secondary pump seal......... appears as a leak from the right rear of the transmission. It's an o-ring that is easily replaced.

With regards to the pan, if it's ever been serviced and the pan overtorqued the gasket is notorious for leaking. I ended up having to replace the pan and gasket to finally get a good seal.

Two other things can cause a neutral besides LOW OIL IN UNIT

the trans filter in the oil pan could have not been changed and its restricting fluid flow

and varnish from old brown colored oil can deposit on the governor valve causing a slow or sticky movement < its driveshaft speed operated > and will also cause a neutral in all speeds < its in all speeds so i do not believe its clutches bands Vacuum kind of thing

you should find and repair any of the small leaks and replace filter in pan re fill with fresh oil to proper level and see if that corrects it -- jz