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Hi all,

I clearly understand that 99% of the forum members have no experience with the diesel engine, but I wondered if anybody could give me an idea of the importance of the 3.21/3.73 ratio when talking about a diesel engine in a 2dr?

cheers!
 

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Hi all,

I clearly understand that 99% of the forum members have no experience with the diesel engine, but I wondered if anybody could give me an idea of the importance of the 3.21/3.73 ratio when talking about a diesel engine in a 2dr?

cheers!
The use of 3.73 makes it easier to powerbrake.

Seriously, I had the 3.73's in my Duramax and had them to keep the RPM's a bit higher to tow with. It's all about ratios in my opinion. Keeping the engine in the right RPM range in order for less down shifts while towing. If all you do is run on the highway without a trailer than you obviously want better mpg and so the revs would be lower. If you are towing something or trail/rock crawling then you need the torque to be with you so the rpm's need to be a bit higher all the time.
 

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Hi all,

I clearly understand that 99% of the forum members have no experience with the diesel engine, but I wondered if anybody could give me an idea of the importance of the 3.21/3.73 ratio when talking about a diesel engine in a 2dr?

cheers!
which motor and transmission do you have?
 

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It is also going to depend on transmission also. 3.21 would be a little tall for a small diesel with 35s. But if the tranny is set up with a low 1st and a tall 5/6th, you might me ok. My dodge I don't use 1st except for heavy towing loads, and on the highway, my 6th is too low to cruise at 75. Would be better with bigger tires!
 

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The gear selection principle is no different on a diesel engine than it is on a gas engine. Look at the power torque curves for the engine and then look the gear ratio vs engine tables to select the best gear ratio for you. Diesel engines tend to have more low end torque so the gear ratios tend to be lower numerically (higher gearing) to enable them to operate a lower engine RPM. Where as the 3.21 provides better fuel economy than performance on the 3.6 it may be ideal gear ratio on the 2.8.

If you read a recent heated debate thread on this subject you will realize that proper gearing is very subjective your personal taste and you are better off understanding the principles and using the tools described above to choose the best gear ratio for you rather than asking opinions on what is the best ratio.
 

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I got a wrangler because I wanted a true off-road car so went with 3.73 on my diesel - not sure about a 3.21. The mpg with 3.21 might be slightly better but that does not matter much with my low mileage.
 
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