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Quad 4x4 is terrible expensive. They sure have a lot of stuff on their site, but every time I've thought about buying something from them, I've found the same thing at about half the price elsewhere.
 

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Hey Wild Chev. you may have a problem there unless you already found a way around it. I moved the speed sensor exactly as you did on the 203/205 set up in the Gorilla.

The problem is when you shift the trans into 4wd the Allison computer looks for the factory GM gear ratio in that case. I am not sure what it is in the stock truck, or if it is different than the 205.

When I shifted the case into 4wd the allison basically goes into a "no go" mode.

I had to move the speed sensor into the adapter and put the reluctor ring on the stub shaft just like the one you got from Advance Adapters.

Hopefully this doesn't jam you up on your project.
 

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Discussion Starter #45
Hey Ian,

I do not see any difference in function of the speed sensor being at the tranny output or at the transfer case output when in 2 or 4 hi. I am guessing that you run into the problem when in 4 low?!?

do you have any pics of your setup? or part numbers?

the np261/263 gear reduction is 2.5:1 and the np205 is 1.98:1 reduction. I am curious if you can just change the perameter in the allison ecm so that it will work with the different ratio.

anybody have any other creative solutions?



Hey Wild Chev. you may have a problem there unless you already found a way around it. I moved the speed sensor exactly as you did on the 203/205 set up in the Gorilla.

The problem is when you shift the trans into 4wd the Allison computer looks for the factory GM gear ratio in that case. I am not sure what it is in the stock truck, or if it is different than the 205.

When I shifted the case into 4wd the allison basically goes into a "no go" mode.

I had to move the speed sensor into the adapter and put the reluctor ring on the stub shaft just like the one you got from Advance Adapters.

Hopefully this doesn't jam you up on your project.
 

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Hey Ian,

I do not see any difference in function of the speed sensor being at the tranny output or at the transfer case output when in 2 or 4 hi. I am guessing that you run into the problem when in 4 low?!?

do you have any pics of your setup? or part numbers?

the np261/263 gear reduction is 2.5:1 and the np205 is 1.98:1 reduction. I am curious if you can just change the perameter in the allison ecm so that it will work with the different ratio.

anybody have any other creative solutions?
Hey Wild,

I do not believe you can change the TCU because it is hard programmed in, and yes it is when in 4 lo that you will find teh problem.

My adapter kit is almost the same as yours with the short spud shaft and the two spacers with the front of the 203 drilled for the 6 bolt round pattern. But I machined the reluctor ring to press onto the "spud" shaft and then drilled and tapped the spacer for the speed sensor.

OBTW, you will hear that shaft "walk" when you are off the throttle at a steady speed. Similar to the sound of a coupler on a Dyno.
 

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Its Looking good man.... Gonna be done for memorial day????
More Pics, More pics....
 

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sweet deal... gonna be nice to see how it does once everything is buttoned up and running! Keep us posted and thanks for taking the innitiative and jumping in to get things done. Much appreciate you sharing with us!

C-ya
 

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can a GM np205 be converted into a "ford" np205? they both drop on the same side? I thought the GM and Ford dropped on opposite sides??
 

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Discussion Starter #51
Done.... again!

Ok so… on my first attempt I had decided to play around with modifying the transfer case output housing because if I screwed it up I would have been out way less money as opposed to the Allison rear cover. However, it was way easier to modify the 4x4 Allison 1000 rear housing to accept the speed sensor.
Now armed with the knowledge that the different reduction ration between the np-261/263 vs. the np-205 would cause the transmission to fail when operated 4-low my new approach was to find a spot to put the speed sensor somewhere between the transfer case input and transmission output. After doing a little thinking the obvious choice would be to attach the exciter ring on the stub shaft and the best place on my application to mount the speed sensor was to go through the transmission rear housing.
I acquired another exciter ring and had it machined to fit on the big end of the stub shaft with a 0.002 interference fit, so that it will not need any bonding agent to stay put. Note: the exciter ring is cast iron, or at least mine was, so care needs to be taken when pressing it on as to not break it. Then I chose a place on the rear hosing that was out of the way of anything important and on the top portion to help reduce the chance of any leaks. Once I decided where to drill I carefully drilled the hole freehand. The speed sensor I used is for a 2001 2500hd, see below pic for part number. Drill bit required is 51/64 and tap is M22x1.5. With the hole drilled and tapped it was just a matter of finding the right thickness washer to get ~0.40 clearance between the sensor and exciter ring, oh and a little bit of silicone.
I decided to leave the other sensor in the transfer case output housing since it was already there and the sensors are cheap. Plus if one fails the other will get me home :p


speed sensor box with part number


stub shaft/exciter ring and speed sensor


exciter ring/stub shaft and speed sensor installed


speed sensor mounting position


final assembly
 

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We use the compu-shift controller on the 4L80 in my Dad's truck and the pertinent detail about it is that it only uses the speed sensors in the 4L80 case and has an entry in the setup parameters to set the low range in the transfer case. And since it's using the tranny shaft only, it really doesn't have to know it's in low range to function. Shift timing is probably a little off but it will work.

This leads me to believe that somebody who knows their way around the inside of the computer could program the stock tranny computer to think that a 2:1 low gear is stock. I know the allison is a whole different deal from the 4L80 but the logic may be similar.

It may be easier to just put the speed sensor on the trans output shaft and call it good till technology catches up with us a bit.
 

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Great work man, this really gets me to thinking of the possibilities now:D
 

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Hey Wild,

I do not believe you can change the TCU because it is hard programmed in, and yes it is when in 4 lo that you will find teh problem..

I know this is way late..but I just found this thread.

YES you can change it. :D

EFILive can reflash the stock allison TCM to whatever ratios and speed sensor pulses you want. Could have saved yourself a lot of time and aggrivation.

ben

 

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I know this is way late..but I just found this thread.

YES you can change it. :D

EFILive can reflash the stock allison TCM to whatever ratios and speed sensor pulses you want. Could have saved yourself a lot of time and aggrivation.

ben


That is fine for a single t-case, but my problem was that I had multiple ratios, that EFI live cannot change.
 

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So....whats the deal with the gorilla? Why is it sitting at fleece?

All new engine harness, live EFI cracked ECU and an upgrade on the trans to the 6 speed. The Banks electronics were good for a race truck, but when it came to daily use, it was imposible to hook up a scan tool for diagnoses, and there was no ALDL connector. Whenever it had a hickup on the road, it would go into limp home mode and I would have to basically diagnose it blind, or just hope it would be gone after a couple of key cycles.

Also, the turbo housings were set to build boost at a very high RPM (above 2400) so he is changing them out so it will build boost lower and make it a little more "usable"
 

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sounds like they have some work to do lol. They do good work though...I never realized that it was the gorilla til they told me.
 

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Is this running yet? If so, how's it working in 4wd???

How are you controlling the allison - standalone controller or stock TCM and wiring harness???
 

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bump to see how this all worked out...

Is it possible to have a female input on the 205 so that the coupler between to two male 29 spline shafts is not needed?
 
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