om617 in a yj lacking any hwy power
 

OK so in the last few months I have installed the om617 engine out of a mercedes 300td into my yj. The yj from stock had 3.07 gearing which wasn't even good with the original 4.2 liter because I had the wise idea of putting 33inch tires on it.
With the 4.2 and 33s I could go roughly 110km or 68mph max! O and 5th gear (manual trans ax15) was never used since there was 0 power because of having 3.07s and 33s

Now i put the om617 into the jeep and trying to hit 100km or 60mph is impossible.
I also wanted to put a ford 8.8 into the rear so I did and it had 3.55 gearing so I changed the front to 3.55 as well. I only installed the 3.55 because the ford axle already had it.

I know I should probably put 4.56s into the jeep or at least that's what I'm thinking because I still can't use 5th gear and I can max hit 100kmh on flat road with the wind behind me hahaha. Seriously no power on the hwy at all!

From all this do you think having no hwy acceleration is all due to my gearing or am I missing something else?!

get a Kubota :tu: No just kidding. You need to talk to Evenglass.
I decided to figure out my gears with cheap used, rear tire only swaps until I find what I like and then make it permanent with a set of gears.
I know it is ugly, but you can try on a "temporary only" pair of smaller tires on the rear only and see what happens. At least you are looking to test smaller tires. I am having to go bigger, to simulate a 2.71 gear
33"'s sound pretty tall for a MB , you may need a 4.88. the MB likes to rev.
I did not think that gear swaps were all that much fun, to do for testing.
Have you tried all the common MB problem areas valve adjustment, fuel filter, ALDA, fresh clutch,

Thanks for the response I agree with the mb wanting to rev higher and I am thinking more and more 4.88 might be more sensable. Now I did delete the alda and I still have to replace the inline filter but I did replace the filter on the engine itself. I have adjusted the valves twice. Let me tell u it sucks to do in the lifted jeep haha. When I did the engine swap I put a new clutch kit and flywheel in.

Do you have a gear calculator? Evenglass has a lifted MB Cherokee did you read his build thread, He goes into rpm ranges and gears and tires and such. my MB Cherokee was normally aspirated and 2wd, so I am working with 27-28" tires. With stock 355 gears and the AW4 auto, I could still hit 55+ with out a turbo, I was never quite sure if my TC was locking up though.
The little Kubota will wind up to 80+, but it would really like a taller gear or a 6 speed double overdrive transmission.
Sounds like you are doing the right stuff, especially the new clutch
good luck

You need to find out what the torque and HP curve is for that motor. Then find a gear ratio that will put that motor in that range at about 55-60 MPH.

Use this gear ratio calculator. http://www.grimmjeeper(dot)com/gears.html

Plug in different tire sizes, gear ratios, and different OD and non OD transmissions to see what will get you to what is needed.

Don

All the given advice is spot on.... Accept for the Kubota part..... The bad rap these Mercedes conversions get it from people not doing the research and trying to run the engine in a way it was not designed.

thanks for the responses. I will definitely take a look at that chart and consider what the best gearing would be. Its been a great engine so far since I mostly drive in the city. I just can't wait to take the rig out camping this summer, this will obviously require the re gear.

Just the other day it was -30c which I think is fairly close to -30f and I forgot to plug it in over night. But low and behold it started!!! Ill let you know when I do my re gearing how it turns out