There is a lot of info on adapters for the OM617 posted in several different threads on this board. IIRC there is even a drawing of one for a 700R4. The stock OM617 has a plate that bolts to the back of the block that serves as a mounting flange for the stock (722) MB transmission. To adapt other thrannies to the OM617 all you have to do is make a plate that bolts in place of the stock one, but has the bellhousing bolt pattern of your desired tranny. Most people make them out of 3/8" steel or 1/2" aluminum.

If you're going to go to the trouble of doing this, I'd suggest upgrading to the 700R4. It is a 4 speed with a 3.06 1st gear a 1:1 3rd gear and a .70 OD 4th gear and it doesn't require a computer to control it. Compare that to the A904 which is just a 3 speed with a 2.84 1st gear and a 1:1 3rd gear. With the 700R4 you get an 8% lower 1st gear, and a 40% higher high gear.

I'm assuming you already have the A904, but with only 125 HP and 180 ft-lbs to work with from a turboed OM617, the lower low and higher high gears will be worth the small extra expense of getting your hands on the 700R4. One from a V6 4x4 blazer will have the small bellhousing (minmizing the overall size of your adapter plate - and making it stronger by reducing its flexing) and the transfer case flange for the Chevy version of the NP231 transfer case - one of the best transfer cases out there for medium duty applications. There is a HUGE selection of aftermarket upgrade parts for the NP231 too since it was used in literally millions of Jeep Wranglers and Cherokees over a 20 year period.

All that is assuming you're going 4x4 of course. If you're doing a 2WD conversion, the 700R4 gearing is still a benefit, but not as big of a concern...

 

The 700R4 is a terrible transmission for the 617, its basically a 5 speed with 2nd gear removed. Even with a VNT the 617 doesn't have enough torque to make it drivable, you'll have to revv its nuts off in 1st but it will still fall on its face in 2nd as you've lost most of your RPMs.

 

That's just your opinion - stated rather forcefully since I'm assuming you haven't actually done it or even seen it done - but just for giggles, since you are so certain that the 700R4 is such a bad choice, do you have a suggestion for a better alternative?

With ratios of 2.70, 1.54, and 1.0 you think the A904 3-speed would be a better choice than the 700R4 4-speed with ratios of 3.06, 1.67, 1.0, and .7?

FWIW, others who actually HAVE put the 700R4 behind the OM617 turbo have found it to work just fine - like this guy
https://www.dieselbombers.com/diesel...0r4-np231.html
Its ratios certainly make it a better choice than the A904 - not to mention it being a stronger better tranny all around.

 

I, for one would rather have a lower 1'st ratio for towing, or just bumping over a log or rock on the trail--sure would make it easier. If you end up not using 4'th due to the gear being too high, then regear axles to make it perfect. Yea, a lot of expense and work, but you get what you pay for in this case I think. 4 speeds will generally always be better than 3.

 

Wrong!! I have found that the 700r4 is way better than the benz trans. The low first gear gets it rolling quickly, then when the boost starts to build it gets 2nd, NOT falling on its face, and stays in its power band in every gear. The added bonus of t/c lock-up makes this trans a definite improvement. This is with a stock motor and turbo.

 

That's an interesting observation - from someone who's actually done the swap and driven the OM617/700R4 combination.

I believe the original MB tranny ratios were 3.68, 2.41, 1.44, & 1.00

Seems like a lot more even "spread" than the 700R4 - which does have a pretty big step from 1st to 2nd (3.06 to 1.67). It never even occurred to me that it could actually be better because it lets the turbo spool before the shift.

Of course the 4.10 axle ratio with 28" or 29" diameter tires vs the stock MB setup of a 3.07 rear diff and 25" diameter tires factors into the whole equation too...

 

The only issue I had with my 700R4/617 was if the lockup engaged in fourth gear at about 40-45 MPH. That would bog the motor down when lockup engaged in fourth at that speed. If you were going 50+, it was not an issue. If I knew I would be going 40 or less, I kept the trans in third and let it lock up at the top of third gear, worked fine.

My SDL had the factory Benz trans, they're not bad, but fourth is 1:1, the first two gears just come sooner than most domestic transmissions. It's not an issue if the gear ratio is numerically low, but the Benz was a slug off the line.

The OM617 Jeep was peppier, but it had low gears.

I drove the thing as a DD for a few months, I experienced all types of city and mid-speed driving, no issues.

John

 

Did you sell it?

 

Yeah, I sold it on E-bay a couple of weeks ago.......

John

 

No, its a physical fact because I understand the powerband of these engines and the gearing they need to accelerate smoothly and efficiently.

Anything that doesn't skip 2nd gear like the 700R4.


No. The A904 would be very slow off the line and have no advantage over the stock transmission.

Wrong. As I stated prior: "you'll have to revv its nuts off in 1st but it will still fall on its face in 2nd as you've lost most of your RPMs."

If lockup is all you need then there are many manual transmissions that are a far better match to the engine.

IF you revv the crap out of it and/or use heavy throttle. If you drive as a sane person or with any intent on decent fuel economy it will be VERY slow acceleration.

Thats just lack of proper tuning.