Harry's Buggy

[M4wdFab]

or what about welding two of those dodge disconnect collars together to make one twice the size since they appear to have a perfect weld bevel already on them?

[mr.mindless]

For 5" engagement, need 15" total to disengage.

[M4wdFab]

For 5" engagement, need 15" total to disengage.

false.  take a 5" spline slug thing and move it 2.5" its disengaged. 

[mr.mindless]

that's sure true. IDK why I was thinking someone said 5" on each side.

Brain fried.

[Harrison]

The splined section on the main shaft isn't long enough to let two collars side by side disengage. The splines are definitely different than a driveshaft slip. I have thought about trying to cut away some of the splines on a driveshaft slip to make my own disconnect but I think I'm ready to give up on custom designs and just adapt one of these:



These have been out for a long time and people seem to like them. 27 spline Toyota is just a hair smaller than the output in the transaxle which originally steered me away from this as an option but but on second thought, that may actually be ideal. I know a lot of people with Toyota t-cases with similar power and weight who don't have any issues breaking rear outputs and I'd rather break that than a transaxle output.

Solid shaft is still the priority in the short term - want that as a spare regardless. The ability to have fwd is really nice for cruising between trails. I went through the cost and effort to build the cutting break into the rig, would really like to maintain that feature if possible.

[Harrison]

Wheeled all year, no real modifications. Some reliability items have been noted, but nothing major. Still very happy.

Would still like to add the rear disconnect back in
Hood and door panels

Bigger rams for a little more steering is on the "at some point" list

Tried on some 42s today. Went well and placed the order. Raceline is having a sale all month long, 20in Avengers are $100ea off, so I guess I'm pulling the trigger on those too.

Hopefully 300Ms aren't in my future (knock on wood)

[etk300ex]

Good job!

[Harrison]

Wow, haven't updated this since end of 2022!

Wheeled all of 2023 and 2024 on 42s. Overall, very happy with performance and reliability.

Couple driveshafts and one rear stub shaft broken, repaired either on trail or at camp and kept wheeling.

2024 it got converter stall speed increased and later in the season a 40hp tune (that immediately ejected the turbine shaft out of the exhaust onto the ground - replaced with good used unit, no issues since after lots of abuse).

Main area for improvement is off the line power. Converter and tune both helped, but it is still lacking beyond what I believe can be explained by turbo lag. I believe the TCM is limiting throttle at lower rpm.

Frank Radlof built a Chrysler 2.4 turbo transaxle buggy and is manually controlling the transmission with a megasquirt based system that just turns shift solenoids on and off depending on what gear he wants. After understanding the concept, talking with him at length, and reading various educational materials on my transmission, I decided to try building a manual controller myself. This will eliminate any influence the TCM has over engine operation and will let me choose any gear I want at any time. Hold 1st for crawling, start in second for bumping/launching, select higher gears for longer drives like Rausch/AOAA.

There are three shift solenoids in this transmission. The manuals have a matrix that tells what solenoids are on in each gear. Initially, I was planning to use one micro switch for each forward gear combined with some relays and diodes to control the solenoids. I built a prototype with a rotary knob on a piece of wood with wires running all over as a proof concept. Grabbed a valve body connector harness and wired it to my board and went for a drive - sure enough, 4 position selector knob on my prototype board gave me gears 1-4 while driving around the yard.



After more consideration for switch packaging and a couple different switch mounting iterations, I created a drum on the trans gear selector that turns all three solenoids on and off based on where the gear selector is. This eliminates relays and diodes, greatly simplifying the system.

I learned in my research that forward gear shifter selections on pretty much all modern electronic transmissions are hydraulically identical and just send fluid to the valve body where the solenoids decide what to do with it. My stock shifter is PRND432 (5spd auto) so while there are detents and shifter positions for D432, there is no hydraulic difference that comes from that mechanical change in the selector position, just the range switch telling the TCM where it is and the TCM decides what to do from there. I have effectively changed that so the shifter is now PRN1234. There are only 4 forward gear detents on the trans so I'm ignoring 5th gear - I'm not sure this trans has ever even shifted itself past 3rd gear since it's been in my buggy anyway so I don't think I'll miss 5th.

Without any other power to the valve body, line pressure is defaults to max. Shifts are very hard. Line pressure is controlled with a pwm solenoid. I have tried using a pwm dc motor controller hoping I'd find a sweet spot for ok but firm shifts and no slippage. With the controller connected, I get improvement everywhere except 2-3 shift becomes very lazy, regardless of where I set the duty cycle on the pwm controller. Still deciding if I want to live with very harsh shifts or one lazy one. Leaning toward harsh and being mindful of shifting under load - not something I expect to ever really be doing anyway.

There are other solenoids in the trans as well but I am ignoring those for my use in order to keep things simple. They are mainly for smoother shifting, converter lockup, reverse lockout when going forward, etc.

Videos below show latest configuration. Design and build are complete, need to clean up wiring and mount box where all the wiring connections are made. In the little driving I've done, 2nd gear seems like it may be nearly perfect for bigger bumps and launching - two footing loads converter and turbo more without pushing through and gives a much improved launch when releasing brake/applying throttle. With stock control, I would have lag off the line and tach out very quickly (90:1 crawl in 1st gear, in 50:1 second gear, Cherokee was 65:1 in 1st gear)

https://www.youtube.com/shorts/vKYpfKpoUmE

https://www.youtube.com/shorts/IyvIuvMeM9U

[dubt]

Very neat. Rad designs makes something similar for the jeep auto trans that was used in xjs.

Sent from my SM-S928U using Tapatalk

[mr.mindless]

I wasn't sure what you meant by 'drum' until the video. all is clear!
I'd probably miss 5th eventually because I want a do-all, but this sounds very hopeful on fixing maybe the last frustration. Does indeed sound a lot like the AW4 fully manual conversion. I wonder if I should take a look at that for my XJ if I decide to keep that to fix overdrive instead of chasing the silly NSS setup that might or might not be the issue

[Harrison]

I wonder if I should take a look at that for my XJ if I decide to keep that to fix overdrive instead of chasing the silly NSS setup that might or might not be the issue

For what it's worth, I had some goofy issues with the NSS on my XJ that were completely resolved by taking the NSS apart, cleaning, and applying fresh dielectric grease.

[etk300ex]

neat!