Jasonbailey

Apparently I had this in the wrong section.

Ok, I have a few questions regarding my transmission. First off I have a 93 d250. If I remember correctly I have a 46rh? I want to eventually make my truck 4wd.
Now, I understand most people will tell me its better to just get a 4wd truck to make it easier on myself for wanting 4wd. However, I like a project so I was thinking of just upgrading my truck little by little. As I understand it the same transmission is used for both 4wd drive and 2wd trucks. The difference being an extension housing. First where can I get an extension housing online? If not online then I'll just have to keep looking at the junk yards or for a donor truck. Also is the extension housing all I need? Or do I need to do anything to the rest of the transmission? I know I'll need a transfer case and a front axle, but for now I'm just thinking about the transmission. Oh, and a shortened drive shaft.

I have since been corrected by patdaly, that my transmission is a A518 not 46rh. But please if anyone can offer more assistance please do so. Also remember, I am new to all of this, I don't understand all of the mechanical jargon. Please dumb down yours answers slightly.

rrgrassi

If you can find a '92-'93 donor truck with the slush o matic, you would be golden as all needed parts are there.

mknittle

Hi Jason,
A donor is really the best way to go. There is a bunch of little stuff that would be really nice to not have to hunt for. like the transmission wiring harness and the 4X4 light that goes in the message center in the dash(not nessary but sort of nice to have). The engine and transmission crossmembers are different too. I am in the middle of basically the same conversion but with a 5 speed now on my 90. It really isn't that hard but there is a lot of little stuff.

thrashingcows

The A518 is also known as the 46RH...same tranny.

You can look through my build thread, or Marks (mknittle). I did the 2wd to 4wd conversion on my crewcab last winter. That should give you an idea of all the work that is involved.

Angry Johnny

Yes and no, when the designations changed they added an arbitrary torque capacity rating, that's the second digit. 6 is for gas engines, 7 was for the V10 and diesel and the 8 is for the diesel as the V10 was already out of production by then.

The 518 however came in various configurations of clutch discs and planetary gears. When talking about a 518 it is important to note what engine it was behind and whether it is a lockup or non lockup as they are different.

mknittle

As a side note I make more work for myself than necessary. I suffer from the " While I'm at it syndrome"

thrashingcows

Well I stand corrected....thank you for that useful information.

Angry Johnny

You're welcome. Typically the diesel 518 is referred to as the 618.

To the OP what you need is the O/D unit from a diesel 518 (618) with 4WD. You could use a V10 version (RH only), the only difference is the V10 had helical cut planetary gears (they're quieter but not as strong) and the diesel versions used straight cut gears, can't hear them in a diesel truck. Also the O/D unit from a 47RH diesel would work as well I believe as the speed sensor gear is in the transfer case IIRC. The RE units don't have a governor assembly so they would not work.

j_martin

The straight gear OD's are hard to come by now. The helical version is more available, and will work.

Angry Johnny

Yeah, really not a big difference.

Jasonbailey

Ok, so I'm still a little confused. Do I need to just get a complete 4wd transmission, or can I get just an extension housing. I think someone told me if I got the extion housing I may as well figure on tearing my existing transmission apart anyway because I'll need a longer mainshaft. Is that correct or can I just get away with the extension housing?

But thank you for the info on the transmissions.