This might be a crazy idea. Our 89 F250 2wd is a peach, only 103k miles on her, no cracks in the interior, strong running 7.3 in front of a C6. It runs out of gears fast. Being a truck driver, I'm familiar with Brownie gearboxes etc.

Has anybody here added a second gearbox on the driveshaft behind the tranny? It would have to vacuum shift or similar, because there's no declutching to shift given the C6 up front.

 

I'm sure gear vendors has a unit for a c6

https://www.gearvendors.com/f2wd3s.html

 

Thanks for the thought, but if I had $10 for every time somebody's warned me about GV's bad attitude, I could do an oil change on my truck. Seems they have generated serious resentment. I'll pass.

 

I've had a GV unit in my '97 F350 4X4, 460, ZF5 for 98K miles or so. Zero mechanical problems...a few minor elec connection glitches...but trouble-free. I've talked with the techs at GV a few times about service intervals and which synthetic lubes are acceptable...they were courteous, knowledgeable and helpful. I'm absolutely satisfied with everything about GV. Please explain "GV's bad attitude"...this is not a rhetorical question...I seek info. Thanks.

 

I asked FTE about them a couple years back when I was deciding what to do with our 4 spd Bullnose (now has a ZF5). I got the comments back about their bad attitude, specifically with regards to outlandish parts prices. It would be searchable under my username. Have you needed service on yours yet?

 

From oilburners:

I am not real fond of the GV for a truck application, though I'll admit that I've never owned one nor worked with one much, and many have had good luck with them.

GV design was originally a Laycock overdrive built for mid 60's British sports cars and subsequently used on other cars as well. It's designed to give a top end high gear for high speed, ie what you'd want in a sports car and also to be easy and smooth the shift. High load, low speed shifting, etc were not factors in the original design. GV beefed up the design some, but it still shares that genesis.

The GV shifts with a hydraulically/spring shifted cone clutch - hydraulic for OD, spring for direct. The hydraulic pressure is generated by a pump off the input side of the gearbox. Line pressure and volume are thus effected by road speed, which is why it's not recommended to shift into od below a certain speed - something like 35 mph IIRC. Below this it may shift, but could be slower (ie more clutch slippage due to being in between gears) and not have enough pressure (not a strong of a clutch force, slippage under load) Thus, using it as a gear splitter is limited, and you have to be careful lugging down in od. Engine braking too could be an issue in OD, since any slippage will reduce the speed of the input side, reducing pressure, causing more slippage..... Low order probability, but worth considering.

At the end of the day, the GV is good when used as designed - as a selectable extra top end gear under light to moderate load. It's not the best option if you're towing heavy, or wanting a gear splitter.

 

Easier to just dump the C6 and install a built E4OD with 4R100 updates. Can't shift a brownie without the ability to float the gears which isn't happening with a C6, even worse the C6 will start to generate a ton of heat as it has no lock up torque converter. I have been the GV route twice and both times the units ended up being pulled for repairs and they ultimately swapped completely.

 

You could do an aux. with an auto, there were lots of 2 ton Chevys in the 70s with Allison’s and 2 speed rears,and I’ve worked on and around some older Paystar class 8s that had HT750s 2-speed air-shift tandems. BUT, you didn’t really split shift em, just ran them through the gears to direct, let off the power and shifted to high, then rolled back into the throttle, using them as 1 more gear. I’d say an E4OD with a stand alone controller would be simpler and easier.... since it’s a 2wd, you’d have room for a MD Allison, if you chose, too.....

 

Then how to control the E40D? My 89 IDI has no engine computer. The E in E40D is for electronic, right?
I found these guys but no info on replacing a C6. http://www.transmissiontuner.com

 

Very simple, for the last 15 or so years you have been able to buy stand alone controllers. They have gotten better and the shifting exceeds anything ford did factory. I used US Shift when I did my E4OD swap in my 68.