What is the difference between an 84 300SD tranny and an 85? - PeachParts Mercedes-Benz Forum

Graplr · #1 09-22-2008, 10:34 AM

So I'm looking for a transmission for my 84 300SD. I'm getting a used one from an auto salvage yard in the next day I have found decent ones for a good price. One is from an 84 300SD and the other from an 85 300SD.

I searched and did a bunch of reading but I couldn't find anything definitive.

I thought I remember seeing that there were some differences between an 84 and an 85.

Thanks!
-Ryan

Actros617 · #2 09-22-2008, 10:42 AM

Did the 1985 300SD trans have an vaccume amplifier (the blue UFO thing on the driver side)

#3 09-22-2008, 10:51 AM

Different stall speed torque converter for one. I believe the crank pilot bearing hole it rides in is smaller as well.

DeliveryValve · #4 09-22-2008, 10:57 AM

My understanding is the '85 is a weaker transmission and is physically different from the '82-'84 turbo trannies. For your car, I would stick with the '84 so there won't be any surprises.

EDIT: It is physically different, but all mounting bolt holes will line up.

Graplr · #5 09-22-2008, 10:58 AM

Quote:

Originally Posted by ForcedInduction

Different stall speed torque converter for one. I believe the crank pilot bearing hole it rides in is smaller as well.

Thanks for the replies.

I do remember now reading about the stall speed of the torque converter. I could simply reuse my old torque converter from the worn out 84 trans.

I'm not sure what the crank pilot bearing hole is?

Are any of the electronics different?

Would I need to modify the 85 to get it to work in my 84?

Thanks!
-Ryan

Shorebilly · #6 09-22-2008, 03:21 PM

According to my copy of the MB publication, Technical Data, Passenger Cars.....there should be no difference.....they all use the 722.303 (W4 A 040) transmission.....1980 thru 1985, when my li'l book was published........

There is mention of different Torque Converters......
126 (USA) starting 1983 have a stall speed of 1450 - 1650
126 (USA California) starting 1985 have a stall speed of 2400 - 2700

There are a couple of footnotes relating to the various testing of National Versions.....

SB

JimmyL · #7 09-22-2008, 04:05 PM

As far as W123's go the '85 tranny shifts much more like a "real" car. Big difference.
Not sure there is enough evidence to determine that they are weaker though....

Graplr · #8 09-22-2008, 09:22 PM

Hmmmm....
The 84 has 150k on it and is $300 +$175 for shipping.
The 85 has 197k on it and is $199 +150 for shipping.

I thought their were some electronic differences, like an extra plug?

What does it really mean to have 'stall speed' difference?

Diesel911 · #9 09-23-2008, 12:32 AM

Quote:

Originally Posted by Graplr

Thanks for the replies.

I do remember now reading about the stall speed of the torque converter. I could simply reuse my old torque converter from the worn out 84 trans.

I'm not sure what the crank pilot bearing hole is?

Are any of the electronics different?

Would I need to modify the 85 to get it to work in my 84?

Thanks!
-Ryan

The Pilot Bearing is located in the center of the rear Crank Shaft hub and depending on the vehicle is a plane thick Bronze Bushing with a hole in the center or a Shell Type Needle bearing.
The very front tip of the Transmission Input Shaft goes inside of and is supported by this bearing.

twr · #10 09-23-2008, 12:52 AM

I had my 84 300SD fitted with a 85 SD tranny it fits perfectly on the 84 the only problem are the electrical connectors they are completely different but some tinkering will solve that , at worst you will lose the electric passing gear if you don't hook up the right wires oh and if you hook up the wrong wires the passing gear will not work but won't burn anything it just wont work until the wires are corrected.

Good luck

twr

vstech · #11 09-23-2008, 09:46 AM

Quote:

Originally Posted by Diesel911

The Pilot Bearing is located in the center of the rear Crank Shaft hub and depending on the vehicle is a plane thick Bronze Bushing with a hole in the center or a Shell Type Needle bearing.
The very front tip of the Transmission Input Shaft goes inside of and is supported by this bearing.

I have never split an MB motor/tranny before... are you saying that the automatic transmissions input shaft passes through the torque converter and enters a pilot bushing on the crankshaft of the engine???
serioulsy?
you mean there is a pass through for it in the TC, and a fluid seal on the TC???
I have GOTTA look at this...

#12 09-23-2008, 12:22 PM

Quote:

Originally Posted by vstech

you mean there is a pass through for it in the TC, and a fluid seal on the TC???

No, the torque converter has a nub sits in that hole to support the weight and keep it centered.

Graplr · #13 09-23-2008, 01:12 PM

I just found a guy selling an 82 300SD tranny locally. I sent him a message but haven't yet heard back.

Sounds a little fishy as he states the SD was in an accident in 98. He pulled the motor and tranny and 6 years ago tried to plant them into a 'rusty' 300D. He claims he tried to jump the battery (I'm using his terms here!) while starting it and 'blew out all the glow plugs'. He claims he then left it sit for 6 years until now.

Seems a little fishy but all I'm really after is the tranny anyways.

So if I can go check it out I will see what mods he did to the tranny. I don't know if he swapped the tailshafts or if he just left everything alone and just installed it.

Graplr · #14 09-26-2008, 10:48 AM

I just ordered an 83 300SD tranny out of FL from a salvage yard with 59,597k on it for $400. They guaranteed it for 30 days. So
I'm hoping all the electronics are the same, if they are not I know I can make them work, but would rather just plug and play!

It should be here next Wed and hopefully I'll get it installed by next weekend.

I'm missing driving my SD. I want to get it back on the road!

85300DT · #15 09-26-2008, 02:25 PM

What electronics? There are none. That tranny will work fine. Just remember to properly seat the torque convertor before mating up the bellhousing to the block..