Hi Folks, Put a cummins in a 05 XLT...runs great however I have no 4x4 low...4x4 high works...Using a Quick Shift 2 trans controller and they insist they are two separate systems. Vacuum lines all check and yes, in neutral-brake depressed...
Any thoughts?

Thanks,
John

 

The vacuum lines are only for the hub engagement, so if 4x4 high works then the vacuum portion is fine. The most likely reason would be the trucks PCM isn't seeing the transmission in neutral. The trucks PCM has to see the transmission in neutral before it’ll allow a shift into 4x4 low range.

There is a wire in the trans harness you can ground out (you'll have to look at a service manual for your specific truck as the color of that wire changes depending on year and what the original motor/ trans combo was), that’ll make the truck think it’s in neutral all the time (which can be dangerous as the truck will start in gear and shift to 4x4 low on demand in any gear, even moving).

One of my Cummins swaps I still use the 5r110 and np273 transfer case, in that truck the transfer case still works and shifts like factory. In my Excursion Cummins swap, I swapped in a manual shifting np271 transfer case at the same time as the engine, which I MUCH prefer (the use of 2wd Low makes backing a trailer into a tight spot with a stick shift transmission easier, no slipping the clutch required, it just creeps along in reverse and you can concentrate on getting the trailer exactly where you want it). And its hard to beat the reliability of a stick in the floor transfer case shifter.
...

 

Thanks...worked before I put the contoller in...Think I'll chase the original wires down, find neutral and switch it with the QuickShift....but it starts in neutral....

Questioned them about whether or not the QS bybasses the PCM altogether and they're response now is yes..so, good call.

 

I would swap to a manual shift transfer case and never have those issues again. No way I would ever go through all the trouble to put a Cummins in it and put the junk electric shift transfer case back in.

 

Well, never took it out...so didn't. I'll go with Antonm23's suggestion and set it up in a place so it can't be activated accidentally...

 

I would keep your NP273 and convert it to manual shift.

the main difference between the NP271 manual shift and the NP273 has syncros that allow shifting from 2x4 into 4x4 high at any speed.

 

You can shift an NV271 in and out off 4x4 high at any speed if the hubs are locked.

 

You can, but it’s a little more dangerous/ hard in the equipment. If your tires are different OD because of uneven wear, uneven tire pressures , or heck even uneven weight distribution pushing down the front more than the rear, then the two driveshafts will spin at a slightly different RPM.

You might get lucky trying to shift it into 4x4 high, or you might end up tooth-to-tooth grinding/ breaking stuff.

Ford even changed the owners manual in the later year 271 trucks to call it “manual shift at stop” because they got tired of paying for all the warranty claims from people that all said they were going less than 15 mph when they shifted into 4x4 and their transfer case just broke.
​​​​​​…

 

Won't hurt anything at all shifting on the fly, Dodge and Ford both used the NV271 and they are shift on the fly in both trucks. Goes in very easily. All the synchronizer in the Ford NV273 does is bring the front driveshaft up to speed so the auto hubs can engage while moving, no need for it if the hubs are already locked, and the Dodge version of both the NV273 and NV271 don't have a synchronizer since it has a full time front axle that spins all the time.
https://youtube.com/shorts/OC7HJ2dAm9Y?feature=share

 

So, following Antonm23's suggestion I found the neutral signal wire, grounde it to the chassis, got in started it up and put it in neutral-stepped on brake and shifted it into 4x4 high then into 4x4 low and it slipped right in...Still only starts in park or neutral so no worries about starting in gear..
Thanks Antonm23!

 

Glad it worked for you. Just be careful leaving that wire grounded all the time, if the dash switch gets flipped to 4x4 low by accident while driving down the road at highway speeds, it will at least attempt to shift and probably destroy the transfer case in the process

Might want to put a safety toggle switch in that ground wire. I've heard about some passengers thinking that the 4x4 switch was the AC fan speed control switch and just cranking it over while going down the road. On a stock vehicle, with all the Ralph Naders still in place, nothing overly bad happens, but in your case, chaos would ensue.
...

 

yeah, that's the plan a hidden toggle under the dash wired as open one way and grounded the other...no accidents!