8 speed auto for JK?

bo9roadking

New member
I see that the 2014 Grand Cherokee has an option for the 3.0 diesel mated to the 8 speed auto and Chrysler has other vehicles with the Pentastar and the 8 speed auto. I'd like the diesel, but it is still an unknown on whether the JK will get one. However, it does look like the 8 speed auto is currently available for 3.6 Pentastar equipped vehicles and it looks like a better option than my 5 speed auto.

Does anyone know if the new 8 speed auto would work with a 2012+ JK? I know there would probably need to be some adjustments for fitting the transmission under the JK, but the 4.696 first gear would be awesome for getting a heavy vehicle moving. The transmission also has two overdrives that might improve highway mpg.

I've been considering a Hemi V8 swap with my 5 speed auto or a complete LS V8 with a mated 6L80 transmission, but the idea of using my Pentastar with the 8 speed transmission and maybe a supercharger would give me more torque down low with the better transmission gearing and more power up high for highway driving. I think this combination would be cheaper than a V8 swap and I could still take my JK to the dealership if I had too for maintenance.

I really like the Motech LS swap, but I'm concerned about getting my JK worked on if something needs repaired. The closest guy that I know who could make repairs on an LS swap is a 2 hour drive away. I don't think the local GM shops would want to touch it and I know Chrysler won't mess with it. My local mechanic that does most of my repairs, said he could look at it, but he was hesitant because of the mix of GM and Chrysler computers and parts.
 

wayoflife

Administrator
Staff member
If you're concerned with repairs, anything exotic like adding super chargers or transmission not intended for your vehicle will give you grief at the dealership.
 

NFRs2000NYC

Caught the Bug
I see that the 2014 Grand Cherokee has an option for the 3.0 diesel mated to the 8 speed auto and Chrysler has other vehicles with the Pentastar and the 8 speed auto. I'd like the diesel, but it is still an unknown on whether the JK will get one. However, it does look like the 8 speed auto is currently available for 3.6 Pentastar equipped vehicles and it looks like a better option than my 5 speed auto.

Does anyone know if the new 8 speed auto would work with a 2012+ JK? I know there would probably need to be some adjustments for fitting the transmission under the JK, but the 4.696 first gear would be awesome for getting a heavy vehicle moving. The transmission also has two overdrives that might improve highway mpg.

I've been considering a Hemi V8 swap with my 5 speed auto or a complete LS V8 with a mated 6L80 transmission, but the idea of using my Pentastar with the 8 speed transmission and maybe a supercharger would give me more torque down low with the better transmission gearing and more power up high for highway driving. I think this combination would be cheaper than a V8 swap and I could still take my JK to the dealership if I had too for maintenance.

I really like the Motech LS swap, but I'm concerned about getting my JK worked on if something needs repaired. The closest guy that I know who could make repairs on an LS swap is a 2 hour drive away. I don't think the local GM shops would want to touch it and I know Chrysler won't mess with it. My local mechanic that does most of my repairs, said he could look at it, but he was hesitant because of the mix of GM and Chrysler computers and parts.

It would probably work with enough fab, but why? The A580 is a proven monster transmission, not to mention, I don't want an 8 speed in a vehicle with a top speed of 90mph.
 

SDG

Caught the Bug
Related question...

Wouldn't an 8 speed tranny be sub optimal for low speed offroading?

Seems to me a 4 speeds is optimal since it gives you enough variation in wheel speed with low to high rpm?

But I could be wrong not knowing what all the gear ratios are throughout those 8 speeds.
 

NFRs2000NYC

Caught the Bug
Related question...

Wouldn't an 8 speed tranny be sub optimal for low speed offroading?

Seems to me a 4 speeds is optimal since it gives you enough variation in wheel speed with low to high rpm?

But I could be wrong not knowing what all the gear ratios are throughout those 8 speeds.

Not really. Im usually in 1st or 2nd when offroading, MAYBE 3rd if I can get some speed (like softer sand in Moab.) Since the 5speed auto lets you hold a gear, you wouldn't gain anything by having 5 more gears.
 
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