transmission issue no 4th gear. 84 280sl
 

I'm copy and pasting this post from the SL forum.
I believe i am not getting into 4th gear. Its a 722.3. The vehicle owners manual says its a 1st gear start. I definitely only feel two shifts when starting out from standstill. When i am in low it does not shift at all. If I start out in S i feel 1 shift only. Then when I shift up to D it shifts only once more.
I am getting to close to 70MPH at about 3800 RPM. I think I should be at like 84MPH with a 351 rear diff. I checked an online web calculator for gear ratio/ speed conversions. I'm pretty sure i got it right. The tag on the Diff. says 351.
I guess i should check the vacuum module on the transmission. The bowden seems OK, but i dont know I'm playing with that now.

Update: / Questions I'm changing the filter now. Is there anything I can check while I have the pan off.
How many quarts are just in the pan, and is there a torque converter drain.
Are there any other suggestions.

According to the data on EverythingBenz - Mercedes-Benz Forum and Web Search Using Google your rear axle ratio should be either 3.58 or 3.69

http://mb.ilcats.ru/part/class/1/ccode/1/cat/048/type/107/subtype/042/group/35

If 4th gear isn't working then here's a place to start looking for trouble

http://www.peachparts.com/shopforum/...eenshot-49.jpg

If you are feeling brave you might want to check the K2 springs in the valve body (assuming you have 3rd the K1 should be OK)...

...but warning this type of messing about isn't for the faint hearted. If you loose bits / mess it up then you'll be looking for a new valve body => expensive.

I've put some hints and tips for this type of work here

http://www.peachparts.com/shopforum/diesel-discussion/323259-722-303-bits-photo-shoot.html

I don't want to appear rude but I'm not getting a warm wet feeling that you can do this work effectively if you're not quite sure if there's a drain for the torque converter...

...there is one by the way - just in front of the oil pan you'll see a kind of grill on the bell housing section. Look up in there and you'll see a little allen head drain bolt. You might need to turn the crank (on the engine) to see the drain bolt. When standing in front of the engine only turn the crank in a clockwise direction.

Please take care! View and use all information given with prudence.

Yes there's a TC drain, just turn the crank slowly and it's in the little gap at the front in the BH. Copper washer under the pan plug, ally one under the TC plug. Same 5mm key as sump pan.

My Euro 1981 280 always starts off in 2nd unless I specifically request 1st. Diff ratio should also be inscribed on flat section on lower left side of diff rear flange. 3.58:1 on my car.

working without a book for now
 

I've had a valve body off before for a bowden cable replacement, but never apart. I am not afraid to do it as long as i have some guidance. I read the threads about installing the shift kit, and that seems pretty straight forward.
The crank pulley has only a ring of small bolts without a center unlike 61x. Ill try the PS pulley. Is it ok to bump the starter with the coil disconnected to get at the drain. The transmission pan is still off. Maybe I'll replace before i try.

It is hard to tell if i am getting a slight grasp of a 1st upon take off. I could check the kickdown switch. I looked for the tag for the differential ratio, but i could only find the part number. It was 115 351 3200. Thats why i thought 3.51.
BTW the pan and fluid looked very clean. I only found a little sludge on the top of the filter.

I don't think the kick down is at fault because you are going up through some of the gears.

not sure if its in Drive/ U.S. speedo in a euro
 

I did the speed calculation with the third gear 1.44 ratio and a 3.59 diff, and it said I would be only at 53 mph or something at 3800 rpm . I'm definitely going close to 70 at that RPM . So maybe its in gear 4.

Have you checked your owners manual - sometimes they have handy information concerning which gear and which speed etc etc

115 351 32 00 is the diff assembly part number. 115 was the first body style that used that part, 351 is differential assembly / housing 32 and 00 designate the specific part.

On the diff casting near the back cover there is a machined area ( the area for the rear cover gasket ) the left lower or right upper will have some stampings, the ratio should be there.

A quick way is to rotate the drive shaft and count how many times it rakes to turn the axle _one_ revolution. Sometimes ,with a non limited slip diff, it is difficult to keep both axles turning at the same rate. In this case, hold one wheel from turning and count how many drive shaft revolutions it takes to turn the free axle _two_ turns.

It really sounds like the trans isn't starting out in 1st. First is a very deep ratio at 3.68, couple this with your possible 3.58 or 3.69 rear ratio and you will know that you have started out in 1st. First is electrically actuated on non 1st start default trans, perhaps the manual is incorect or a different trans was installed at some point.

With your deep diff ratio and pretty good 2nd and 3rd ratios, you would never miss 1st if you didn't know it had it. First is a " free " ratio that does not have any additional gear train parts over a 3 speed, it just has more valve body parts to make the proper elements engage to generate 1st gear.

[QUOTE=97 SL320;

It really sounds like the trans isn't starting out in 1st. First is a very deep ratio at 3.68, couple this with your possible 3.58 or 3.69 rear ratio and you will know that you have started out in 1st. First is electrically actuated on non 1st start default trans, perhaps the manual is incorect or a different trans was installed at some point.
[/QUOTE]

You got it. I have realized it only starts in first when the selector is in L. When i shift up to S when driving it pretty much double shifts straight into third. When I start out in S, or D it starts in second and shifts normally into third and fourth.
I guess it is o-k like that. I will keep playing with the bowden cable to get the shift points where I want.
thanks for the help


btw I'm trying to think of a tutorial or something I can contribute to the community, but it seems people have mostly got me covered on that.
I was thinking a good W123 sunroof repair tutorial would be cool. I did that job quite successfully. It was not easy. I'll try to think it up. Im just not very well organized with my posts and all, so we'll see.

4 gears are working
 

I dont know how but the combination fluid/filter change, and a bowden adjustment and I have all four gears starting in first. I used Redline ATF. I went ahead and gambled on the top shelf stuff hoping it would pay off. I think it did. Who knows though , it could have been just the bowden. I went over the fill line by about as much as is between the two lines on the dip stick. I dont think it is a big deal. Its only a third of a quart I believe. I'll get it out when i can.
thanks again

Congrats on the fix but ....
 

Our cars are supposed to start out in 2nd. The procedure for forcing a First gear start normally is:

When at a stop, place the shift lever in the lowest gear position, then return it to Drive position.

The transmission will then start out in First gear. Every time you come to a stop, the procedure has to be repeated if you want to continue First gear starts.

Not sure about that.
 

Why does my MB 280sl owners manual state that it is a first gear start. It does not say anything about first gear start in my 300d owners manual. I don't see why it would say that in the 280SL owners book if it were not true.

Sorry, you are correct
 

I have found some information that states all MB auto tranny went to 2nd gear starts in 1986 for Fed mileage standard reasons. For those vehicles, my procedure for first gear start applies.