Mercedes OM603 in a '99 Cherokee
 

Hey all,
I am very interested in doing an MB OM603 (6 cyl turbo diesel) conversion to my 1999 Cherokee Classic and have some thoughts and questions. I already have the engine in my current d/d - a 1990 300D of which I transplanted the 603 into when the 602 failed.
So, first off, anyone have any knowledge as to the fitment of the 603 into an XJ? I know the 5 cyl 617 engine seems to be the popular diesel choice but man I really love my 6 cylinder!!!
Second, I have no use for 4WD where I am and this would be a d/d so that stuff would be coming out, replacing the front drive axle with a straight 2WD axle. I figure the straight axle would be easier to work around or modify with that front-sump engine not to mention the weight savings - any thoughts there?
This is still in the planning stage but the first thing I need to know is whether the 603 is a good candidate for this.
Thanks,
Martin

The oil pan sump will be your only problem. But with the straight axle you may be okay, the steering arm is the problem. I am doing a Cherokee with a 606 engine and had to extend the front sheet metal. See pics at Turbo Diesel Engine Installation, Conversion, and Alternative Fuels-North West Diesel Offroad, Athol, ID

Thanks for the reply, Zeeman.
I have seen those pics - awesome job, did you extend the front for the intercooler(s) or for the engine fitment itself?
Don't tell the guys at the Cherokee forum but I was definitely considering swapping over to a front-steer rack & pinion setup if need be :).
Thanks again,
Martin

The front extension was for engine fitment as well as intercooler room. Nothing wrong with a rack & pinon, but a axle mounted rack is hard to get the steering shaft to work right because it has to slide. Stock box is the way to go and modify the pan.

Ok, so three years later I'm resurrecting this build. It has been thru several incarnations - first the idea of the Benz OM603, then maybe an Olds 4.3 diesel (turned out to be junk), then a GM 6.2 (too big although it actually fit in the engine bay), then a VW 1.9 TDI (which is now in my 23' Penn Yan boat) and now full circle back to my OM603.
The 603 has been pulled from my DD and seems to fit nicely in the XJ's engine bay and I am fabbing up engine mounting.
As stated earlier I have pulled the 4WD stuff and put in a regular straight front axle. I'm using a rear sump oil pan & oil pump from an OM648 CDI engine so that will eliminate oil pan clearance concerns.
I picked up a 6-speed manual gear box but, with the Benz shifter assy, it is waayy long so I have decided to go auto instead and would really like to adapt a 700R4. Having the Benz auto presents a problem in that it is not designed to be able to let the driveshaft slide in/out with the up/down travel of the rear axle.
Not really liking the idea of paying nearly a grand for the transmission adapter kit so does anyone have any experience with making their own adapter?
I'll get a few preliminary pics up as soon as I can.
Thanks,
Martin

you lost me there a bit, what trans is in the jeep? why do you want to change transmissions? what transmission do you have or want, 700r4, MB or jeep?
depending on your skills and shop set up buying an adapter can be money well spent. have you contacted Nathan at mercedesdiesel4x4.com?
if you can stay with the jeep AW4 or AX15, you will save a lot of work with drive shafts and transmission mounts

have fun

Okay, sorry about that. Currently the only trans I have to work with is the MB unit
https://cimg7.ibsrv.net/gimg/www.die...dc6bfc0a33.jpg
but it does not utilize a slip yoke to allow for driveshaft movement that occurs with rear axle up/down travel. I was thinking of the 700R4 because of that reason and also because it has OD (plus lock-up converter) and there is an available adapter kit. mercedesdiesel4x4 only has an adapter for the OM617 engine which has a completely different bolt pattern. However, I just discovered that the pinion yoke of the 8.25 is the same size and number of splines as the tail shaft of the MB 722.3 trans so I could use that and a slip-spline driveshaft - problem solved for 1/3 the cost of the adapter kit - just wont have OD.

Not mounted in but it fits well with plenty of room front & back.

And I just happened to save the front driveshaft which is a slip spline.