Auto Transmission and Ambient Temperature

[mdsalemi]

Despite the fact that my car is running better than ever, there are some conditions in which bad behavior shows up.  One of these situtations, perhaps the most annoying, is the behavior (which includes shift points, smoothness of shifiting, and any other metric you care to use) of the automatic transmission when the car is hot, and specifically when the ambient temperature is hot--like above 90 degree F, +/-. (I should note hot is relative; the temperature gauge is reading normal operating temperature)

On the way down to PUB, there is a stretch of road between highways, so to speak, that is lots of traffic lights, and there was heavy traffic.  Temperature above 90 degrees, but the car's temperature was just a needle's width above that 180 mark.  But the shifting?  Horrible.  Sometimes it went from 2 to 4 so fast that you didn't even know it stopped at 3.  Other times it didn't really want to shift.  Other times, lots of hard klunks.  Nothing consistent, but what I would simply call "bad behavior".  This isn't new, but now that other issues are solved one by one, I turn to the remaining ones.

Now, cool down the ambient air to the low to mid 80s, or most evening running, and all is well.  How much of this hot-air bad behavior, if any, is normal?  Any suggestions?

Personally I don't like driving my car when it is 95 degrees out--but sometimes you can't avoid it.

Something is very sensitive to ambient temperature--and I wonder if it is internal (transmission itself) or switches, etc.

[reggie]

Michael, Yesterday was pushing 20 dg, in sunny Yorkshire,   I did an 80 mile round trip, I noticed on the way home, how smoothly the gear changes were, Compared to local running, so i think it must be to do with the fluid at different temps, Thinner means smoother 

[mdsalemi]

Reggie--not making sense here.

20 degrees is our 68; that's *cold* by my standards of hot ambient temperature.  Your fluid viscosity--any fluid--would be thicker at that temp.  Maybe you mean thicker is smoother?  Should I find a different fluid?  It's always been this way--from synthetic Amsoil (Dr. Benz) to stock MB stuff (last change)...

[reggie]

Michael, What i mean is, My car changes better when its warm, 20dg is warm for us poor folk, Surely my oil is thinner when warm  ,

[Cees Klumper]

Hi Michael - I've never noticed any difference in shifting characteristics depending on ambient temperature (or any other conditions for that matter). On other cars, sometimes they've behaved differently when the engine/trans was cold as opposed to warm, but that's about it.

Probably an auto trans specialist (AAMCO comes to mind, are they still around?) would be able to diagnose this / tell you straight away what might be causing this.

I don't recall this ailment to have ever been reported on this forum before BTW, but I am sure this is quite annoying so curious as to the cause and solution.

[JosephBach]

I drive my car daily when its 115 degrees f in AZ, in heavy traffic occasionally, and I never notice a change in shift quality.... always consistant and smooth.
although i do recall a while back using regular off the shelf dex/merc fluid and it seemed quite fussy and loud, then i switched to hurst ATF meant for non-computer controlled race transmissions, and to this day the trans is smooth as butter.

[Sirasila]

My car goes through the same jump from 2nd gear to 4th with only a fracture of a second in 3rd as well when running on the highway in Thailand where it's always hot and most days are above 90. I'm also experiencing the same symptoms as mdselami is.   I've always wondered the same thing.   Waiting to hear what others are saying as well.   

[Benz Dr.]

The full synthectic is practicaly a life time fill. Why did you change it and what was it doing with that stuff as compared to now?

[mdsalemi]

I would disagree that the full synthetic is a near lifetime fill.  An automatic transmission has moving parts, metal moving parts, as well as a filter.  They should probably be changed at "regular intervals" and that time frame can mean many things to many people.  Certainly there is no harm in a new filter and new fluid.

That being said, the second fill of my transmission was with fully synthetic Amsoil, by you.  The transmission has always behaved this way, (with origiinal fluid; Amsoil; and back to original.  Fluid has not had any effect) but it is hard to pinpoint and duplicate because it requires high ambient and operating temperatures, perhaps combined with hard driving (i.e. stop and go) to go wacko on me.  Then of course, you need an expert to diagnose what is going on, when it is going on...

Some of my car's issues over the years have been quite esoteric and I've lived with them for a long time before solving them.  This is probably no different.

The only other thing I can say is this: when the original transmission was in the car, with the main seal leaking, AND some fluid had leaked out, the transmission behaved a bit strange when low on fluid.  There are probably a few similarities in behavior, except the current transmission is not low on fluid and it gets funny only when very hot.

[wwheeler]

Michael,

Do you have the double acting trans solenoid on your '69? My '68 111 solenoid was defective (intermitent of course!) and was causing similar problems. With a new one, shifts and performance is consistant hot or cold. Solenoids in general don't like a lot of heat. 

[mdsalemi]

Wallace,

That's the first piece of sound "sounding" advice/suggestion I've heard.

Can you tell me how to find this out?  Is this something I can see underneath the car?  Since it is intermittant it sounds like it should be replaced, and perhaps next summer will tell...

[Sirasila]

is it the same thing as the 3 positioning solinoid from the tech page like in this pic? how much is a replacement?

[wwheeler]

That is the solenoid. I don't have a lift, so I had someone replace it. They said they had to lower the trans to get to it. You can see it and observe it's operation by removing the access plate on the right side of the trans tunnel.   

I know the set up is different on the post '68 or so cars, so I can only tell how mine is set up. There should be many posts that describe the solenoid operation, so I won't go into that. The three positions are: down (at idle and low pressure), middle or nuetral (anywhere between idle and kickdown and medium pressure), up (kickdown onlyand high pressure). The higher the pressure, the harder the shift. Mine would occasionally be lazy going from neutral to down or idle. The new one is a solid movement. The old one also would only sometimes go into kickdown and then wouldn't go back to neutral. So that is why I was getting hard shifts then soft shifts.

I checked all the wiring and switches with a multimeter and they always worked. So replacing it was the last option. I don't recall the price from the Classic Center, but it wasn't cheap. I wouldn't replace it unless you know it's bad.

Michael, Why wait until next summer to test? Come to Texas! We still have at least 7 more days of 100+ which is on top of the 56 days we've already had.

[Benz Dr.]

I disagree with the idea that synthectic won't last longer but I'm not going to try and convince anyone otherwise even though my 30 years of runing it clearly says so. A filter change and top up would be all you need.

 The solenoid can sieze up. I've seen this a few times along with the linkage going to the modulator. It will work but may not release or not come on. High heat could make it worse so it kind of makes sense.

[mdsalemi]

I disagree with the idea that synthectic won't last longer...A filter change and top up would be all you need.
High heat could make it worse so it kind of makes sense.

I did not say or suggest that synthetic would not last longer; they generally do as you know.  Heck, I've run Mobil 1 engine oil for 16,000 miles, but still change it every year.  I believe that any fluid in an automatic transmission isn't a lifetime fill.  Even on the modern MB units which were sealed as lifetime...ask someone who had to have one cracked open and worked on.  But I digress.  For the record, when I had to drain the better part my transmission to change the radiator (an awful lot of tranny fluid came out of those hoses...) most of it was pretty darn clean.  I strained it just to be sure and put it back.  I did have to top it off as you suggest; was probably down about 20 oz in total, some lost.

I don't believe the solenoid is seized per se, because it must be functioning; the car runs great today.  I do believe Wallace's assessment however, and your concurrence that high heat might make it worse.  So, that will be next spring's project.

[J. Huber]

Only to add my experience to the discussion... My car shifts pretty smoothly most of the time but every once in awhile feels like somebody is kicking me in the rear end! I think this has less to do with the ambient temp than with the amount of throttle versus speed (if that makes sense). If I am rolling along a flat or slightly uphill grade and am increasing throttle, the car usually shifts smooth. If on the other hand, I am coasting and maybe letting off the throttle (down a slope perhaps) the car will shift harder. I don't mean a downshift -- that I feel too but in a normal way -- I mean as I pick up speed but without pedal acceleration, the upshift will clunk. To smooth it out I can almost anticipate this and give it slight throttle. It's an art 

[Benz Dr.]

When you lift off on the throttle it creates high manifold vaccum and this will make the transmission shift much more softly than WOT. If you have harsh shifts with light or no throttle, the modulator needs to be adjusted.

The solenoid can be partialy seized and still work. Sometimes it will work properly and other times it won't work at all. The more you drive the car the more it gets used and that may factor into it but once they get sticky it rarely improves.
I came up with a way to remove the solenoid quickly. It involves some cutting of sheet metal so I give everyone the option first.   

  Synthectic is nearly a life time fill for our cars. You can't compare a new car to our cars because the average 113 gets a couple thousand miles every year at most. I drive mine more than that but I use it for longer trips.
A full synthectic will out last regular ATF by several times. Only an oil wear test can tell you  if you need to change it or if you're throwing away good oil. The colour means nothing.

My expirience with synthetic motor oils goes back to 1980 so it's not just my opinion.
 I have a combine that we bought new in 1982. It has about 4,000 hours on it now and all I've ever used is a 15W40 para synthetic. We have changed engine oil in this machine about 5 or 6 times as opposed to the 40 times it would have taken with dino oil - that's a lot of used oil to get rid of.
 I can still see the part numbers on the valve springs - it's that clean inside of the engine. Everything shines like the day it was made. I'd be happy to show anyone. No, I don't sell Amsoil anymore but long term tests like this are pretty hard to dismiss as being pie in the sky.

[mdsalemi]

Dan--just more reason to confirm I should change my solenoid next year.  Sorry Wallace, don't want to do this now nor drive to Texas to get hot weather!

[wwheeler]

James,

It wouldn't hurt to check the adjustment of the throttle switch. It is what tells the solenoid that the throttle is at idle and decreases the trans pressure. Your downshifts would also be a little hard as well if this were the case. But dosen't hurt to check and easy to do.

[Benz Dr.]

The thing about this job is that you can't get at the solenoid. You can on the right side but not on the left side. Dropping the back of the trans involves a certain amount of work that takes at least two hours to complete.

[mdsalemi]

The thing about this job is that you can't get at the solenoid. You can on the right side but not on the left side. Dropping the back of the trans involves a certain amount of work that takes at least two hours to complete.

Understood.  Don't believe I'll tackle this myself.

[Benz Dr.]

Just because it's you Mike, I'll tell you how I do it.

On the passenger side of the car there's an access hole but there isn't one on the drivers side. I make a new one, complete with a cover, the same dimensions as the passenger side and then it's very easy to get at. You need a plasma cutter to do this job.
 
Mark out the new hole according to the dimensions on the other side of the tunnel and cut the hole smaler than the templete. Drill holes for mounting the cover and seal underneath. Making the hole and cover will take longer than removing the solenoid.

  Like I said earlier, I leave it up to the owner to decide if they want to go this route. Making access holes is a common repair for fixing 114 blower motors ( THE job from hell ) and installing non ZF transmissions is 113 cars.

[mdsalemi]

Well, Doc--thanks for the tip.  I would NEVER try this on my own; I don't own a plasma cutter and won't be buying one soon.

The medical community, (in case you didn't know) would call this an "invasive" procedure.  It may take more time, and cost more to drop or lower the transmission, but nobody is going to be cutting holes in my car!  I'll leave it to a pro.

[Benz Dr.]

I am a pro. And, I said that I would ask first which proves I'm a pro.
 Any questions?