Delayed auto tranny engagement when cold - normal or not? - PeachParts Mercedes-Benz Forum

Flounder · #1 01-30-2009, 11:05 AM

Hi fellow dieselers: When I start my '81 CD cold and put it into either reverse or forward there's a 10-12 second delay before the gear engages. It only does this once then the rest of the time after warming up it's fine. If I let the car cool down for 5-6 hours then it does it again.

I don't think it had this delay last winter. Fluid level is a tad high. I'm wondering if the pump inside the tranny could be getting weak.

My other question is, is this function vacuum controlled? If it is then is it possible my vac pump is getting weak? All other vac functions such as brake booster seem to be fine.

Does anybody else's trans do this in the cold?

rrgrassi · #2 01-30-2009, 11:17 AM

Fluid and filter changed recently?

MBNRA · #3 01-30-2009, 11:23 AM

No, 10 to 12 seconds isn't normal. How does it drive and shift otherwise? The first thing I would suspect is low transmission fluid level. You ARE checking this on level ground with the engine idling in Neutral, right? If it needs a fluid and filter change, this could be a cause too.

Flounder · #4 01-30-2009, 11:48 AM

Thanks for the replies already. Yes I changed the fluid and filter just about a year ago, which would be maybe 24,000 miles. If anything the fluid level is a little high.

Fluid is nice and red. No burnt smell or anything like that.

It shifts just fine. No problems at all other than the initial delay engaging into gear when cold.

So could this symptom indicate I'm headed for big-time tranny trouble?

rrgrassi · #5 01-30-2009, 11:58 AM

Quote:

Originally Posted by Flounder

Thanks for the replies already. Yes I changed the fluid and filter just about a year ago, which would be maybe 24,000 miles. If anything the fluid level is a little high.

Fluid is nice and red. No burnt smell or anything like that.

It shifts just fine. No problems at all other than the initial delay engaging into gear when cold.

So could this symptom indicate I'm headed for big-time tranny trouble?

It's possible. I had a Chevy truck do that. The torque converter impoded, and took out the entrire tranny, except the case.

Being an 81, it may just need a band adjustment also.

MBNRA · #6 01-30-2009, 12:26 PM

Quote:

Originally Posted by Flounder

Thanks for the replies already. Yes I changed the fluid and filter just about a year ago, which would be maybe 24,000 miles. If anything the fluid level is a little high.

Fluid is nice and red. No burnt smell or anything like that.

It shifts just fine. No problems at all other than the initial delay engaging into gear when cold.

So could this symptom indicate I'm headed for big-time tranny trouble?

That's hard to say. It is really cold out where you are now and I live in Arizona. It could need a band adjustment, but I wouldn't panick about the torque converter imploding on you. These are not Chevy's. They are made well! Torque converters going to pieces under hard use and rapid acceleration are not all that uncommon in a GM car! GM racing even has rules and reg's for racing dealing with torque converter explosions and special bell housings are required because sooner or later, this is expected!

I've yet to hear of any Mercedes benz having a torque converter go BOOM!!!

Stop guessing and the next time start your motor and let it warm up and then time how long it takes to go into gear with a stopwatch. Almost any wristwatch has a stopwatch feature. Try this and report back.

rrgrassi · #7 01-30-2009, 12:31 PM

I agree, these are not GM trannies...

That said, what condition are the shifter bushings in? When cold, put selector in L and see if it engages faster or not.

Flounder · #8 01-30-2009, 01:04 PM

rrgrassi: I think you might be on to something there. I forgot to mention if I shift it down into L (lowest notch on the selector) it will usually engage right away.

But I don't notice any problem with the detent positions any other time. After I've driven it 3 blocks even when it's 28 degrees out it engages normally in either R or D.

The more I think about it maybe I should just go ahead and change the fluid and filter this weekend. It can't hurt.

Thanks for the helpful ideas everybody.

babymog · #9 01-30-2009, 01:26 PM

Common failure mode.

The seals are getting hard, aren't elastic enough to compensate well for the changing sizes with temperature changes. Once warm they expand and seal well. Until then, there are internal pressure leaks which make the transmission incapable of operating properly, once the pressure normalizes with the seals warmed up it is fine.

Chances are that it'll operate that way fine for quite some time provided you aren't revving it up to engage gears or driving with a clutch slipping. Better would be to have it checked and adjusted, seals replaced if necessary.

bgkast · #10 01-30-2009, 03:51 PM

From what I have heard the only fix is a rebuild.

compu_85 · #11 01-30-2009, 04:28 PM

So what's the normal delay? My SDL goes into forward gear after about a second, but reverse takes 2 to 4.

-Jason

bgkast · #12 01-30-2009, 04:35 PM

I would gess less than a second when they were new. Mine takes 1-2 seconds.

rrgrassi · #13 01-30-2009, 04:40 PM

Quote:

Originally Posted by babymog

Common failure mode.

The seals are getting hard, aren't elastic enough to compensate well for the changing sizes with temperature changes. Once warm they expand and seal well. Until then, there are internal pressure leaks which make the transmission incapable of operating properly, once the pressure normalizes with the seals warmed up it is fine.

Chances are that it'll operate that way fine for quite some time provided you aren't revving it up to engage gears or driving with a clutch slipping. Better would be to have it checked and adjusted, seals replaced if necessary.

I had one that worked until it got warmed up. Hot, thinner oil would push past the seals. The shop suggested just to reseal. I opted for complete rebuild.

compress ignite · #14 01-30-2009, 09:48 PM

I believe stevebfl has commented on this anomaly.

Unfortunately,it's one of the first signs of the need to start saving up for
that "Reman",We all pray will never become necessary.

79Mercy · #15 01-30-2009, 10:00 PM

Before you rebuild it put in a can of Transx it might condition the seals in the front pump so they seal better at all temps. It can hurt since you need another tranny anyway. Give it a shot.