Gen 2.5: 4.90 gear swap Q's

[BEG]

I have the opportunity to pick up a set of 4.90s from a local '03 Sport which I'd eventually like to swap into my '00 Gen 2.5 with stock, unlocked 4.27s. I'm still in the planning stages, but I have some questions I need answered:

Front diff:

- Can I swap the whole front axle? Just the carrier? Gears only? (Front will be getting an air locker so gears will have to be set up regardless)
- If I swap in more than just the ring and pinion, that means I can no longer run CAD, right (I plan to run manual hubs either way)?
- Will I lose 2HI if I want to still be able to shift into 4HI on the fly?

Rear diff:

- Does the whole third member from the MS bolt right into the Montero housing?
- Is keeping the Hybrid LSD worth having to install an ARB rear locker?
- Does it make more sense to just install the R&P into a factory locked rear?

 

[jeep-N-montero]

Sorry, but did you even bother to search for the answers to any of your questions, because I know for certain they have all been answered before on here.

 

[BEG]

I did a google search on 4x4wire and here. It's not always easy to find specifics. Most threads are just focused on which model Sports to source 4.90s from. If there are specific search terms or threads I should look for, I'd be glad to do so.

 

[KyleT]

I second, if you swap the whole front housing, will that give you full time 4wd regardless of the case position?


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[eurosonic]

check out my build thread bud

 

[BEG]

check out my build thread bud

Thanks, Eurosonic, that helps a lot (front R&P swap info starts on page 51, for anyone interested). How did losing the central axle disconnect affect driving? Did MPGs go down? More wear on drivetrain parts?

 

[eurosonic]

Truck felt more responsive, fuel economy slightly better. Got 30 more miles per tank


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[BEG]

BTW, just wanted to add a basic recap of Eurosonic's front R&P swap:

The whole front axle assembly can swap in if you transfer the axle mounts from the Gen 2.5 onto the Sport axle.
The new axle eliminates the central axle disconnect assembly. I assume all vacuum lines are traced back to the source and plugged.
The 4x4 light will flash constantly in 4WD.

 

[BEG]

I second, if you swap the whole front housing, will that give you full time 4wd regardless of the case position?


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My understanding is that the front drivetrain will remain connected but there won't be any power going to the front wheels unless you're in 4WD. If you have manual hubs, you can disconnect the front wheels but everything inboard of the hubs still spins. I could be wrong.

 

[BOPOH]

subscribed maybe next summer i'll part out my Sport for this upgrade

 

[plh]

My understanding is that the front drivetrain will remain connected but there won't be any power going to the front wheels unless you're in 4WD. If you have manual hubs, you can disconnect the front wheels but everything inboard of the hubs still spins. I could be wrong.

You are correct. To stop the spinning you will need manual locking hubs. Even with the normal CAD setup, the CV shafts and jack shaft spin as stock. Manual locking hubs disconnect this action when unlocked and reduce this wear. If you had the M.S. front differential without manual hubs, the front driveshaft also will spin even in 2WD. CAD stops the driveshaft, ring gear & pinion by disconnecting the passenger side spider gear inboard of the jack-shaft.