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Hey guys! Not sure if this is the correct spot for this question but hoping someone can lend some advice.

Recently swapped a OM617 engine from a 1985 Mercedes into my 1983 CJ7 with 33x12.50 tires. I didn't have the time and money for a Trans upgrade so as of right now it has the T5 in there. I'm still trying to figure out the gears that are in there right now, the Jeep was a project to say the least when I first got it and all info from previous owner was incorrect...

Anyways... The issue I am having is when I am changing from 3rd to 4th gear. I feel like I have to rev 3rd pretty high for a while to go into 4th. No matter what 4th bogs pretty bad and I have to play catch up. I keep getting in that "in between" issue where I'm running out of 3rd gear but 4th isn't there yet.

I know it's not great info but I am planning on figuring out what gears I have and getting a tach soon to figure out exactly where I'm at when cruising and shifting.

Any ideas?
 

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Hey guys! Not sure if this is the correct spot for this question but hoping someone can lend some advice.

Recently swapped a OM617 engine from a 1985 Mercedes into my 1983 CJ7 with 33x12.50 tires. I didn't have the time and money for a Trans upgrade so as of right now it has the T5 in there. I'm still trying to figure out the gears that are in there right now, the Jeep was a project to say the least when I first got it and all info from previous owner was incorrect...

Anyways... The issue I am having is when I am changing from 3rd to 4th gear. I feel like I have to rev 3rd pretty high for a while to go into 4th. No matter what 4th bogs pretty bad and I have to play catch up. I keep getting in that "in between" issue where I'm running out of 3rd gear but 4th isn't there yet.

I know it's not great info but I am planning on figuring out what gears I have and getting a tach soon to figure out exactly where I'm at when cruising and shifting.

Any ideas?
Well you can get a good idea of the T5 gears via google.

I think you might want to take a look at that engine. Diesels are notorious for responding well to new governor springs, turbos, bigger injectors, etc.

A quick google of the stock power numbers for that engine and im not very impressed. I would look into some cheap quick upgrades for the engine to help it come to life. Its stock CR ratio was only 21:1 which seems kind of low for cylinder pressures by todays standards at least. (for a diesel engine)

Your Axles could also 2.73 gears too.

You should figure out what gears you have and good from there.

If you have a crazy highway gear I would adjust that first. If you are still not happy after that I would look at things for your engine.
 

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What rpms are you turning when shifted into 4th? I had two Benz OM617 turbo cars (79 300 TD & 83 300 CD). Both were totally gutless until the turbo was spooled up. There was close to zero torque off idle.

Personally, I do not understand the attraction to diesels in Jeeps. Most are heavy (including the OM617), don't like to start when it's cold, and don't put out that much torque or power. A 350 sbc crate engine will out perform all most all of them and are one hell of a lot easier install, not to mention the ease of getting parts for.

But I'm just a geezer-----
 

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Discussion Starter #4
Well you can get a good idea of the T5 gears via google.

I think you might want to take a look at that engine. Diesels are notorious for responding well to new governor springs, turbos, bigger injectors, etc.

A quick google of the stock power numbers for that engine and im not very impressed. I would look into some cheap quick upgrades for the engine to help it come to life. Its stock CR ratio was only 21:1 which seems kind of low for cylinder pressures by todays standards at least. (for a diesel engine)

Your Axles could also 2.73 gears too.

You should figure out what gears you have and good from there.

If you have a crazy highway gear I would adjust that first. If you are still not happy after that I would look at things for your engine.
Looks like I have 3.31 gears so not stellar to say the least. Pretty sure that is my problem right now. I have so many other things on the list to address with this thing but changing the gears out first and then addressing more engine mods. This engine came out of an 85 300D and I had it looked over top to bottom to make sure I wasn't putting a junker in the CJ. Everything looked good but it was bone stock.

It's either going to be 4.56 or 4.88 gears. Still tossing around the idea of which one to go with. This Jeep is my cruiser, not much highway but it won't be uncommon for it to see 60 mph. Very little off-roading.
 

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Discussion Starter #5
What rpms are you turning when shifted into 4th? I had two Benz OM617 turbo cars (79 300 TD & 83 300 CD). Both were totally gutless until the turbo was spooled up. There was close to zero torque off idle.

Personally, I do not understand the attraction to diesels in Jeeps. Most are heavy (including the OM617), don't like to start when it's cold, and don't put out that much torque or power. A 350 sbc crate engine will out perform all most all of them and are one hell of a lot easier install, not to mention the ease of getting parts for.

But I'm just a geezer-----

Still needing to get a tach to show the exact RPM I'm at when shifting. I thought about swapping a 350 into it but I know a lot of guys doing that. Of course I wanted to be different, plus I'm a big Benz guy so I always wanted to do this swap. Install on this engine choice was not bad at all.
 
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