1985 300SD about 205k on everything but the engine itself which only has about 150k on it.

*If you would like to read the abridged version of this tale, please see the meager few lines at the end.


My transmission has never shifted correctly since I got the car in late August of 2004. (over two years ago.) But it was not this bad.

I always keep my fluid level just under the max line.

Before I replaced the motor mounts, the belt cut through one of the AT cooler lines. I am sure that there was a couple of days there when I drove the car with too much fluid in the transmission. I got a new hose ASAP, but the fluid level was too high after adding fluid I thought I had lost from the cut line.

Bottom line, there has been too much fluid in it before.

I did research, found that it may be a vacuum problem. From all the things I have read, I deduced that without any vacuum going to the transmission's modulator the transmission should still shift on time just harshly. I disconnected the vacuum, and for a while it was much much better.

Recently I drained all the fluid (from TC also) replaced the filter, and replaced the pan gasket and crush washer. ( I had a leak at the pan gasket ) Even with torquing all the bolts to spec, it still leaked though not as bad. When I replaced the fluid, I must have put too much fluid back in. (did not check it correctly)

So then I drained more off until the fluid level was correct. I re-torqued the drain plug but it did not seal quite well enough. (did not happen to have a new crush washer) The fluid level was too low, and finally I got the level spot on.

Fluid level has been maintained to be just below the max line.

Now today while driving (still no vacuum to the modulator) the transmission flares heavily going into all gears. I will expain ;

1-2 shifts late about 3500 rpm with pedal depressed all the way down (without kick down switch engaged) Shifts OK when pedal is half-way, but still a bit late.

2-3 never shifts when pedal is depressed fully. Only shifts when you let off the pedal, then start going, then let off again.

3-4 shifts late in the same manner as the 1-2.

Also tonight, for the first time I started smelling something odd which must be burning transmission fluid.

The down shifts all 'clunk' and specifically the 3-2 down shift is very rough and takes a good second to occur. Noticeable clunk also when slowing down to a stop, but not all the time. (2-1?)

It takes the transmission about 2-3 seconds to engage into gear from park or neutral.

*Abridged Version

-Tranny has about 205k miles on it.

-The Fluid level has been overfilled on two different occasions, once for under a week, and the last time for only a day.

-Fluid level currently and when I drove it tonight was spot-on.

-There is no vacuum hooked up to the transmission.

-All shifts flare significantly, but especially the 2-3.

-I have (just this evening) begun to smell something odd, which may be burning ATF.

-Down shifts all clunk, the 3-2 is significantly delayed (at least a second to down shift) and there is a very noticeable clunk when slowing to a stop under most conditions (2-1?)

-It takes the transmission about 2-3 seconds to engage into gear from park or neutral.

My question(s)-

Should I replace the fluid again, and try trans-x and do the K1 spring also?

Is there anything I can do? What would you do?

Does it sound as if my transmission is toast?

Was it ruined by my overfilling? (my research says it may have been)

-This really makes the car a hassle to drive, and it is no longer as enjoyable as it once was.

If you spent the time to read this thread, please vote and tell me your opinion as to what I should do.

Any and all help is appreciated.

Thank you in advance.

So.. is the ATF burnt or not? You said you have a leak, could some leaked fluid have gotten on the exhaust system and "burnt" that way?

You're supposed to be able to smell it from the tranny dipstick, so it shouldn't be too difficult to know for certain if the fluid inside the tranny is what is burnt.


I voted you should do the trans-X and spring kit. If tranny is toast, you can't hurt it any worse, and you may find out for certain about the tranny when you open it for the spring kit.

__________________
'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

You've got a few problems there.

1) The harsh shifts are cause by the lack of vacuum to the modulator.

2) The flaring is caused by internal wear in the clutch paks. The K1 would definitely help the 2-3 shift. The addition of proper vacuum to alleviate the harsh shifts may make the flaring worse.

3) The late shifts are not caused by a loss of vacuum, but, are common when the kickdown switch is stuck. Disconnect the kickdown switch and drive the vehicle. See if any improvement is noted. Another possibility is a Bowden cable that requires more slack. Increasing the length of the cable will bring the shift points down on a properly working unit.

4) The transmission is clearly near the end of it's life.........but........I wouldn't characterize it as "toast" quite yet.

The K1 spring and proper vacuum modulation might buy you some additional time with it.

Do as Brian suggested and you may get some more mileage out of it. These trans are tough and you can usualy limp them along for quite awhile.

If you have the time and money have your rebuilt. Figure about $1k if you do the removal yourself.

__________________
1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I have started to smell something peculiar in the passenger compartment... it just started recently, and I thought it must be the ATF burning. I do know that the leak did not get ATF on the exhaust.

I will check the ATF level and note its smell.

That looks like what I am going to try.

1. Alright.... I can deal with harsh shifts, just not the extreme flaring.

2. I will buy and install the K1 spring kit ASAP. Hopefully this will help.

3. This makes the most sense. I did not even think of trying that. I will go check on this immediately. Thanks

4. Alright, thank you.

Thanks for Chiming in so quickly Brian, I was hoping you would. This makes the most sense, and I am going out right now to check the kickdown switch and the bowden cable.

Thanks again.

Try to get through the winter on that trans. Perhaps you can come up here for spring break and we can put a new trans in, if thats the route you take. Between the 2 of us, and maybe Roy if he's nice, can get it done in a day. I've done these trans swaps 2 too many times.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

I have the time, because I do not rely on the car to get me anywhere that I have to go. (ie. I don't need it to get to work or school)

I have enough money to get mine rebuilt, but part of the bellhousing is cracked. Would that only matter if I am returning it as a core? I guess if I get mine rebuilt then (while out of the car) I could clean it up, and have the bellhousing welded back together... is it just aluminum?

Would getting it rebuilt include things like a new pan, a new modulator etc? or would I have to buy those types of things extra?

I can definitely do the work myself.

Thank you all for your advice.

I think I could limp through the winter. We'll just have to see. I need other work done also

Thanks for the offer, Ill call you sometime.

Alright.

I just unplugged the kickdown switch, and screwed in the bowden cable adjustment nut all the way. (most slack)

The car shifted much better while cold, but when warmed up it still flared on all shifts, and now it is even harder to get it to engage into 3rd gear.

The fluid looks very red, and does not smell burnt. While checking it I have been dripping some onto the exhaust, which creates the smell I am getting.

The level of fluid has been maintained at just below the max mark.

I am going to try to not drive it until I can get a new gasket and the K1 kit.

I hope that will help.

Thank you.

Well, the unplugged kickdown switch and the adjustment to the cable was simply requested to reduce the rpm's of the shifts. There was no intention for these adjustments to have any effect on the flaring........and they didn't.

So, since you simultaneously did both items, probably need to plug the kickdown switch back in and see if it's the culprit for the high rpm shifts.

One other possibility that may fix the flaring is to increase the modulator pressure. There is a small T handle at the modulator that allows you to do this. More pressure will firm the shifts and stop some of the flaring. Do a search on "modulator" to find the precise procedure for it. The T handle unfolds, you turn it clockwise a couple of turns, and the fold it back into position.

Alright, I just got in from plugging the kickdown switch back in. The bowden cable must have been the problem, because plugging the switch back in made no chage.

Right now there is no vacuum going to the transmission's modulator, because my vacuum system is all out of whack. I have played with all the adjustments (except the modulator) Here is the facts on my vacuum system.

Amount of Vac. at idle = >20" ( I did just rebuild my vac. pump.)

Amount of vac to modulator at idle (when engine is cold) 10", but I can adjust it to start off anywhere from 20" to 0"

Amount of vac to modulator at idle (when hot) 20" but I can adjust it down to about 15" using the vac. amplifier adjustment.

All associated rubber has been replaced.

Booster works correctly.

Vacuum system holds vacuum after engine is shut down.

When hot the VCV does not change the amount of vacuum going to the transmission more than a couple of inches. I have tried and failed at adjusting the three different VCV's that I have to make them work correctly. All work the same way.

I think the differences between hot and cold can be attributed to that switchover valve that is in the loop.

What to do?

Firstly, you stated that you're running the vehicle without vacuum to the modulator, correct?

And, it flares under this condition, correct?

If so, the addition of any vacuum to the modulator will make the flaring worse. So, you've got to increase modulator pressure to cut the flaring dramatically. Then the issue with improper vacuum can be addressed to, hopefully, prevent any banging on downshifts.

The 20" vacuum to the modulator at hot idle is way too much. Please confirm that you measured the output from the amplifier to the modulator and not the output from the VCV to the amplifier.

Sorry, I should have been more clear.

The vac line that goes down to the modulator is currently disconnected and blocked off. It does flare under this condition.

So, I hook the line to the modulator back up, and turn the modulator t-handle twice clockwise as you described previously?

That is the reading that I read (with my mityvac) at the output of the amplifier which goes to the modulator.

I know that the vacuum should be about 15" at idle, and drop down to 0" or near it when the valve is in the full pedal position.

I saw you posted in a different thread that you have one of your cars at 8" at idle.

Could you give me more numbers as to what would be correct on my car?

Also, I read in another thread that in my car (because of the vacuum amplifier) that vacuum to the modulator will not drop to 0" until boost has been taken into account by the amplifier. Is this true? should I hook up a vac gauge (T into the line) going to the modulator to see how much vacuum I am getting under load/and boost?

Thanks-

You've got something between my SD and my SDL..........a bit of a unique situation, so, my results may be somewhat different.

But, certainly, the vacuum at idle to the trans must be in the range of 10-11" (or less) if you want to prevent the flaring.

In reality, however, we're ahead of ourselves, because any vacuum whatsoever will cause increased flaring due to he reduced modulator pressure. The first thing to do is to adjust the modulator for more pressure and see if you can stop the flaring with no vaccum connected. If so, then we can proceed. If not, then all the discussion about vacuum is moot.

Remember, that K1 kit will have a real benefit on the 2-3 (the worst one for flare). Seriously consider installation of that kit, in additon to the modulator adjustment.

I've not adjusted the modulator pressure on these. Maybe someone who's done it can comment.