Allision 3500 series transmission, transfer case options

[rm6keith]

I found a good deal on a GMC T7500. I like the power of the Isuzu 7.8l motor. My problem is not finding a suitable option for a Transfer Case behind the Allison 3000 & 3500 RDS/EVS series Transmissions. (The 3 available to me in Automatic).

Marmon Herringtion makes the T30 direct bolt on transfer case, but the only one I found was $18,000.

Some options would be another transmission that is common and currently 4x4 that I could source the transfer case that would take the power of the 7.8l Isuzu. But I feel the stock transmission already programmed for the vehicle may be easier. I am currently stumped on how to get a transfer case to the back of this engine/transmission combination.

I have searched the Forums and found nothing at all. I may not be searching correctly?

Any ideas to convert the T7500 to 4x4?

Thank you,
Keith

 

[Grenadiers]

How about a divorced transfer case? That’s what we have in our Saurer. But in our case, it’s attached to a divorced automatic transmission! Are there any similar trucks to yours already 4x4 to research?

 

[rm6keith]

Grenadiers,

I did think about the divorced Transfer Case, but wanted to see if there is a bolt on available. I read how some divorced transfer cases are 1100lbs. I am really only familiar with the NP205 and a little overwhelmed at which transfer cases would work for me. What model Transfer Case are you using?

I see the Rockwell T1138 Transfer case and T138 divorced transfer cases are available for 5 ton trucks. (military surplus mostly). I do not mind some manufacturing for a Divorced Transfer case, but getting a T case I am not familiar with is a little intimidating. I am hoping for some direction on which models I should be leaning towards.
Keith

 

[SootyCamper]

Wonder what kind of parts interchangeability there is with the Isuzu FTS? I imagine you could snag the 4x4 parts for a decent price.

 

[Ozrockrat]

You could go with the 7th gear option for the Allison. Same setup as used in the M-1078 S&S trucks. They bolt straight up to the 3000 series Allison and provide a low-low gear and AWD. Like this one eBay Listing

If you are looking outside of that the Rockwell T-1138 has an overdrive in high which is good for some applications. There are also the Axletech T600 but they are getting harder to find (350 lbs).