Buying a 2005 5.9

[Mule19]

I want a 5.9 and have locked on a solid one. I have a few questions however what axles are used in a 2005 I believe it is AAM and then what differentials where used in the rear? The previous owner did a factory fuel filter delete and the an air dog system, I would like to put a cat filter kit where the oem one was it is that overkill?

 

[Travelin Ram]

It’s an AAM diff. If you’re lucky it’s the LSD which is helical gears, not clutches. Works well and doesn’t wear out prematurely.

The CAC (intercooler) was a known weak component that year. Plastic end caps just like a cheap radiator.

 

[mtnrider]

Be sure and check out the front end good, that is a big week point of the gen 3 HD trucks. Ball joints, hub bearings, tie rods, track bar bushing, ujoints etc.
Since they did an air dog I'm guessing they may have been modding/tuning the motor as well. Proceed with caution.

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[Mule19]

I’ve already accepted the fact I’ll have to replace all sorts of bushings and bearings. I’m mechanically skilled so doesn’t bother me. Owner says just the tunes that come with a edge tuner for fuel economy.

 

[Mule19]

It’s an AAM diff. If you’re lucky it’s the LSD which is helical gears, not clutches. Works well and doesn’t wear out prematurely.

The CAC (intercooler) was a known weak component that year. Plastic end caps just like a cheap radiator.

Any way to tell besides cracking the cover which lsd it is?

 

[Travelin Ram]

The fastest way to test a diff is put one tire in the grass and one on the street and see what happens when you goose it. Easily accomplished on a test drive. One wheel peel: open diff. Both spin with unequal traction: LSD.

Any tuner is a big red flag to me. It’s a common cover story to claim fuel economy. I’ve tuned several myself and never once did the fuel economy get better.
Tuned trucks are really hard on transmissions too. Those were barely adequate for a stock Cummins.

Full disclosure- I bought a 2005 new. Tuned it. Broke it, fixed it.

Not saying this is a bad buy, just what a prior poster said, proceed with caution. Stock, or properly modified they are an awesome truck. I wish I’d kept my 05.