Over drive and divorced T-case?

[coachgeo]

for improved MPG....

I've heard rumors of 1.75 reduction gears at the hubs and I've been trying to track a set down. The 3116 [CAT engine] needs to be spinning ~1800pm for best fuel consumption. I've also pursuing a reduction hub eliminator kit which would get cruise rpm to that range, but not sure how well that will work.

makes since if all one wants is a more roadable higher MPG rig. Not though if you want to have capable off road abilities as well. Looks to me (and I've not looked REAL close) is potential better route to go may be to stuff an overdrive or 2cnd gear box* in there somewhere between engine and tranny or tranny and T Case. For example, remove T case and install overdrive there then put a divorced T Case with High (1:1) and low ratio. Either it a 2cnd gear box or just overdrive you'll end up with a more traditional 4x4 set up instead of full time 4wd..... not a good or bad thing... just a different thing, BUT you do end up with both better ratio for 4x4ing AND for off roading.
Not being full-time 4wd would help fuel milage also I would think.

I don't know if such animals (overdrive / cascade box) exist that would mate up to the CAT or either end Allison transmission, nor if a divorced Tcase exist that could take torque of the CAT etc.

* Say a two or three ratio Gear box stuffed in there. Miight even get you a lower AND higher ratio out of tranny. Best of both worlds?


NOTE- Took this above quote and made this new thread so not to hijack the thread the above quote was found in.

 

[DiverDarrell]

I think this is part of what your thinking of.

https://www.marmon-herrington.com/oem/t30.php

nevermind it's AWD... 30-70 split.

i did see a YouTube video of a military auctioned off transfer case air operated with high and low range. Was a divorced set up. But could give you 2wd. Without being able to disconnect the front drive line from the tires, there wouldn't be much mpg gains as you still have all the frictional loss to rotating parts.

 

[coachgeo]

I think this is part of what your thinking of.

https://www.marmon-herrington.com/oem/t30.php

nevermind it's AWD... 30-70 split.

i did see a YouTube video of a military auctioned off transfer case air operated with high and low range. Was a divorced set up. But could give you 2wd. Without being able to disconnect the front drive line from the tires, there wouldn't be much mpg gains as you still have all the frictional loss to rotating parts.

Interesting. The information did say it could handle AWD.

That being said though the AWD portion of this rig I do believe is located in the Tcase. So if one removed the stock Tcase and swapped to one like the above it would no longer be AWD. I could be wrong though
Also it says it can be done as a divorce mount in the info as well.

 

[DiverDarrell]

The divorced transfer case I was thinking of is the axletech t600. However I'm not sure what is modified on the transmission for the current t-case set up. I do believe they share the same oil. So to convert the current setup to a divorced set up may have some hidden surprises. You would also need to fab up all the new brackets and ideally huck bolt to the frame. As been said before welding the frame will weaken them.

 

[coachgeo]

The Tranny as you folk now is an Allison 3000 series. Apparently there is some flexibility in gearing of these. two overdrives are available in the tranny. Not sure what is in it now.

Allison Transmission’s 3000 Series is designed for medium-duty commercial vehicles and is engineered to adapt and operate efficiently in a variety of applications. The 3000 Series includes close or wide ratio gearing and a maximum rating of 336 kW (450 hp). The addition of 5th Generation advanced electronic controls enhance operation and prognostics capabilities. An optional integral output retarder for better vehicle braking and reduced brake wear is also offered. With up to seven available speeds, including two overdrive ratios and several engine-driven Power Take-Off (PTO) provisions, the 3000 Series is built to make medium-duty vehicles more fuel efficient and easier to operate.

Tranny is model 3700 here is the spec sheet from Allison. Not sure if this is how they went into the LMTV though. Also below is Literature on other Allison Tranny's that might can be used. Lot to decipher. would 4700 be better for Expedition like use??View attachment int3700_sa5343(201306)blk.pdfView attachment SA3748EN%20-%20Voc%20Model%20Guide%202013.pdf

 

[73m819]

The drop box also has 1 st in it, not in the trans, if someone were to replace the drop box with a standard transfer case, they would end up with drive lines at a VERY sharp angle, this will KILL drive line u-joints, just a thought.

 

[coachgeo]

The drop box also has 1 st in it, not in the trans, if someone were to replace the drop box with a standard transfer case, they would end up with drive lines at a VERY sharp angle, this will KILL drive line u-joints, just a thought.

Some Tcases are Clockable allowing for turning them to a point where they match best with the desired driveline setup before final fitment.

Sure first is in the Tcase? Does not seem to compute with PDF of Allison Tranny.... or Im reading it wrong.

 

[73m819]

The trans has nominal 2 to 5 with low in the drop box along with the 30% to 50% front tractive effort clutches, since the drop box is not a 2 speed (another great design by the design committee), low has to be first gear. The drop box is PART of the transmission as a single unit, not two separate units bolted together to make a single unit ( like the 1009s trans and tranfer)

 

[DiverDarrell]

Thanks for that good information 73m819. I was under the impression that the drop box was a bolt on and not integral to the tranny casting. They brag about making the truck with off the shelf parts, but that change makes it a lot less common 3000 series transmission. I guess the only way the op could do this is with another 3000 series transmission set for rwd to a transfer case. Would need new computer, programming and a few hand fulls of $$$. And ctis may become Inop. As for the A1 you would need cat to also reprogram the engine tranny interface.

Its to to bad today's kids can't drive a manual, a full synchronized 9 or 10 speed would have made this truck a lot better. At least for what I will use one for.

 

[coachgeo]

if you look at the PDF drawings it is most certainly bolted on. Well the case for it is at least. If that means any of Allisons other TCases etc. can be swapped onto it by mix matching parts that is a different story.

 

[scottmandu]

I've seen hemtt transmissions that used a divorced case.. Not sure if the gearing works out well however as those trucks are speed limited to and have much taller tires.