Ben

Hi,
Well I'm not so much having problems with my transmission, but just trying to figure out why my engine is revving like a 3 speed auto at a given speed.

I know that my cars transmission has been replaced at some point, and I wondered if it was possible that it was actually changed out with a 3 speed.

I looked right on the transmission by the rear cross member, and I have no code, so looking on the code next to the oil pan, I have the numbers:

722 270 21 01 722 326 0 3040515

I cant find a reference to this particular number anywhere in the WSM. The nearest match says its a A28.14. Can anybody confirm this?

My ATF reservoir has the filler on the angle, instead of the flat topped reservoir, so its a later transmission than my car should have.

Where do I look to find out my rear end ratio?

Steve Cattaneo

Your transmission is a 4speed which starts in 2nd gear as do most Mercedes transmissions. For a 1st gear start use manual “2” or WOT acceleration with kick down switch under the gas pedal actived.

Ben

I dont think I was that clear,
For example, in top gear, at approx 120 MPH, my engine turns at about 5k rpm, similar to what a 3 speeder would be turning.
I'm now curious as to whether my rear end has been swapped with a 3 speed's 2.75 (if this is even possible) or then again, it could just be the 2.64 that a A28.14 should have, and my tach or speedo is out.

Schocki

Go to google and do a search for gear speed calculator. It will show numeroeus programs that can help you figure it out e.g. http://www.kabamus.com/garage/gears.html

danglerb

5k rpm at 120 mph doesn't sound to me like you are in top gear with any possible rear end ratio. I would have a shop that knows about the 928 or at least the Benz tranny take a test drive, once around the block should be enough for somebody that knows what it should be like to tell if its wonky.

Ben

With the 3 speed rear end (2.75) in top, its 25.64 mph/1000rpm, so thats about what i'm getting.
Remember, this is a euro car, so I think the rear end ratios are a bit different compared to the US versions. I'm sure the car is in top gear, I counted 2 changes from a standstill, not using kickdown.
Should there be a number stamped in the diff housing somewhere that would indicate what I have fitted?

danglerb

Driving the Autobahn at 132 MPH and 5500 RPM does not sound right to me at all, but I know zip about the AT. I did find this old thread with some id info, but can't say I understand it.
https://rennlist.com/forums/928-forum/271496-auto-trans-number-on-side.html

Porken asks:
Can you tell if an '84 trans has LSD from the 722... number stamped on the side?

722 27 12 1 722 316 02 526060

Steve answers:
The number 12 stamped on the intermediate plate, between the transmission and differential identifies the differential as 40% LSD. A28/08/12…..

The seventh and eighth digit stamped on the transmission pan rail identifies the model and year of the transmission. In your case it’s a 12, which is an A28. 01 4speed, USA and Canada, 1983/ 1984 model. 722 270 12.
__________________
Steve Cattaneo www.mastertechtrans.com

C.F.

Ben
Jack up the rear & crawl under the back taking a wire brush with you so you are looking up at the rear edge of the diff. The pic shows what you should see
The No's in the pic are for a manual G28xx, a 4 speed auto should say A28xx , I think 3 speeds are A22xx. the xx in the No. designates the gear ratio/model of trans.

Ben

CF, I have a series of holes drilled there. I'll post a pic later when i'm at home. It looks as if someone didn't want people to know what it was, and drilled a series of shallow holes to remove the stamped lettering.

danglerb

Stolen parts maybe? Doesn't seem like a good way to reduce the weight.

Ben

Here we are, as promised. Sorry the quality isn't very good, it was with my cellphone in the dark.

I'm assuming this is where that stamp would have been.

Ben

Ok,
So tonight while driving my Benz, I noticed that if the shifter was in '3', then the transmission would use first gear under normal driving, ie. not under kickdown.
Maybe as previously suggested, my shifter needs adjusting, and i'm not actually getting fourth gear. I dismissed this theory because I could count two upshifts when driving (2-3-4) but what I could actually have been counting was 1-2-3.
Will give me something to play with in between changing out my 5.0 engine for a 5.6 in my mercedes this weekend.

Ben.

Giovanni

So this number means the car did not have LSD as a factory option unless the bold number was 12??
A281216H00957

Thank you...

Imo000

Yes, I think that's right.

Here's a post I had about discussing if my parts car had a LSD or not. There is a mention of 12 starting at the bottom of the first page. https://rennlist.com/forums/928-forum/314902-help-lsd-or-no-lsd-update-it-is-lsd.html

At the end it turned out that it did.

Giovanni

Imo000, in your case it was 12 was the 6th and 7th digit or is it the same for the 4th and 5th digit?

Thanks....