Will it work? 1985 300D 722.315 trans into 1982 300SD with 722.303....? - PeachParts Mercedes-Benz Forum

pawoSD · #1 07-10-2009, 08:52 PM

I am looking to buy a transmission from a 1985 300D to put into my 1982 300SD with a recently failed trans.....I know the 300D has a 722.315.....my 300SD has a 722.303

Main question here is: Will it work? Is the '85 trans different in any way that would prevent a successful swap? I know the 300D has a mechanical speedo....would I be able to swap the tail piece from my 300SD trans onto the 300D trans? I read in some other threads various things about a pilot bearing difference......tail piece size difference....etc....

So I am wondering if anyone has done this or knows for sure the differences.

pawoSD · #2 07-11-2009, 12:47 AM

Anyone?

rs899 · #3 07-11-2009, 06:33 AM

Since you are desperate I know enough to tell you that if both are 722.3xx the tailshaft housing can be swapped so that your speedometer works. I think I have read that the 85 TC is different, so keep that with its tranny. The vacuum controls changed in 85 so you will need to sort that out. I don't see why it wouldn't bolt up, though, a 617 is a 617 is a 617...

Somebody must have done it and talked about it here..you searched?

pawoSD · #4 07-11-2009, 10:45 AM

Quote:

Originally Posted by rs899

Since you are desperate I know enough to tell you that if both are 722.3xx the tailshaft housing can be swapped so that your speedometer works. I think I have read that the 85 TC is different, so keep that with its tranny. The vacuum controls changed in 85 so you will need to sort that out. I don't see why it wouldn't bolt up, though, a 617 is a 617 is a 617...

Somebody must have done it and talked about it here..you searched?

Yeah, I did some pretty extensive searching and it does look like the tail swap and actual install should go fine....now my primary concern is with the vacuum setup.....what is the actual difference between a pre-85 and 85 vacuum setup? What does the 85 one do that the others do not?

I will be keeping the '85 torque converter with the trans and will swap that in with it.

DeliveryValve · #5 07-11-2009, 10:54 AM

You can keep the '82 vacuum setup. Also the '85 torque converter has a 2400-2700 rpm stall speed up from the '82 converter's 1450 - 1650 rpm. This would be perfect for a 2.47 ratio diff swap your thinking of doing.

pawoSD · #6 07-12-2009, 12:43 AM

Quote:

Originally Posted by DeliveryValve

You can keep the '82 vacuum setup. Also the '85 torque converter has a 2400-2700 rpm stall speed up from the '82 converter's 1450 - 1650 rpm. This would be perfect for a 2.47 ratio diff swap your thinking of doing.

Will there be any downsides with a higher stall speed torque converter and a 3.07 diff? I am not sure if I will be converting my car to a 2.47 any time soon.....or will this just make my car have even more juice off the line?

So essentially, with my current torque converter, if I punch the throttle off the line, the engine is able to get as high as 1650rpm or so.....then it has to push with what it has.....whereas with the '85 converter, it allows the engine to go into the even better torque range of 2400-2700rpm while accelerating off the line. Right? If that's correct that sounds pretty awesome.

I read online that higher stall torque converters make a lot more heat than lower stall ones......is this the case? Maybe I'll be extra anal and add an aux trans cooler at some point....

DeliveryValve · #7 07-12-2009, 07:54 PM

Quote:

Originally Posted by pawoSD

Will there be any downsides with a higher stall speed torque converter and a 3.07 diff? I am not sure if I will be converting my car to a 2.47 any time soon.....or will this just make my car have even more juice off the line?

So essentially, with my current torque converter, if I punch the throttle off the line, the engine is able to get as high as 1650rpm or so.....then it has to push with what it has.....whereas with the '85 converter, it allows the engine to go into the even better torque range of 2400-2700rpm while accelerating off the line. Right? If that's correct that sounds pretty awesome.

I read online that higher stall torque converters make a lot more heat than lower stall ones......is this the case? Maybe I'll be extra anal and add an aux trans cooler at some point....

Yes, your car will take off at an optimized torque range. I don't see a problem of using it with a 3.07. But it would be great for a 2.88 or 2.47. Not sure on the heat statement though.

pawoSD · #8 07-13-2009, 01:10 AM

That should be awesome! I am eager to get this underway.....except now my 300E is misfiring, so I might not even be able to make the drive tomorrow to pick up the trans....

Blasted Gassers!!

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