^^2
i've also thought about doing this to mine as a next life and found that it was less expensive and more reliable going that route. however i've never heard anything about different tuning.
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2wd to 4wd conversion
- Thread starter Dazedandconfused
- Start date
^^2
i've also thought about doing this to mine as a next life and found that it was less expensive and more reliable going that route. however i've never heard anything about different tuning.
Here is a link for the ABS, although the 2wd truck might not have the programing to utilize the speed sensors. http://offroad.automotive.com/106217/0905or-dynatrac-abs-retrofit-kit/index.html
It's all good. I'm still not understanding how the speedo will not work properly with the divorced setup? Seems to me that the truck will still think it is a 2wd & not care about what is hanging off the back of the allison. Am I missing something? What is happening eng, trans, transfer case tuning wise when put into four low?
There might be some trickery that can be programmed into the TCM via some different T/H parameters (basically setup the T/H tables as 4lo tables and lose a properly functioning T/H button) to get it to shift correctly in 4lo with T/H engaged but otherwise, if the ECM/TCM don't know it's in 4LO and are only getting the VSS signal from the tailshaft of the alli, it won't be shifting correctly. It'll think you are going 40mph (hypethetical number) because that's how fast the alli output is spinning when in reality you would only be going say 25mph because it's in 4lo. Again those likely aren't the correct numbers unless I got lucky :angel: but I think you get the point. So, the trans. is shifting at certain points based on a number of inputs - RPM, VSS, TPS, etc. and now those numbers are screwy because the VSS signal is incorrect. How could it possibly shift correctly and when you want it to?
On the other hand, if you put the VSS on the output of the xcase (divorced or otherwise), and don't let the ECM/TCM know when you've engaged 4LO, then it's still going to shift like it's a 2wd/4HI which is not ideal for running in 4LO.
I'm pretty sure that was the argument presented to me in my thread about the proper placement of the VSS and the tuning of the ECM/TCM. I REALLY hope someone can correct that if they know where I've said something wrong or have misunderstood.
I don't have all the answers but I have looked into this pretty heavily and it's not just a slap-it-together deal to have everything work correctly like a factory 4wd truck. Getting all 4 tires to turn isn't the hard part IMO, it's getting the electrical parts to work like they should for 4lo.
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You type to damn fast
. I get what your saying now. Wonder what it would take to move the sensor to the tail shaft of the divorced t-case. I will have to look into it. Thanks for the info.
I'm pretty sure putting a tone ring and sensor on the output of a np205 can and has been done for other applications. I'm pretty confident you will still have to let the computers know when you put it in 4lo because good shifting for 2wd/4HI is not going to be good shifting pattern for 4LO but without switching to other tables when it gets the signal, it's only always going to shift based on one (or two if you use T/H for something other than T/H) table - 2wd/4HI - because it's never going to be told otherwise.
C-ya
C-ya
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You could take EFILIVE and modify the low range ratio to 1:1 and then take the ground wire and connect it to a switch that triggers in 4 low. This would give you the different adaptives and shift tables for 4 low without having the speed sensor post transfer case. The problem would be with ABS, but like stated already the SFA would probably require the loss of that anyways unless you went with a late model FORD front end or something. The DURAMAX buggy is not using a post transfer case speed sensor in his set-up, but rather he's using the SUNCOAST tailhousing and drilled it for a speed sesnor. The whole reason behind putting the speed sensor after the transfer case was so that the OSS would always read vehicle speed. And it was easy enough to put in a different shift schedule in the TCM with a multiplier in it. And also GM chose to make the tranny shift completely different in 4 low. The only reason GM put the speed sensor in just the transfer case was it was the cheapest way to make everything work together with what they had.
the np205 isnt gods given gift to the 4x4 world that everyone thinks/assumes it is. Yeah its gear driven and has a cast iron case, whoptee frikkin doo. Whens the last time you heard of a 1000+ rwhp dmax splitting open a stock chain driven NP261/263???
not to mention its low range (1.96 or whatever it is) isnt anything to write home about.
I bet you could break a 205 behind a dmax a LOT easier than you guys all think...
ben
not to mention its low range (1.96 or whatever it is) isnt anything to write home about.
I bet you could break a 205 behind a dmax a LOT easier than you guys all think...
ben
It's already happened Ben. Now, with some of the beefy gears and some attention to the output shaft I'd say they will be alright in a tuning-only 500rwhp street type truck but it's well documented that they will not last behind a big torque diesel if pushed hard such as in the case of sled pulling or boosted 4wd launches. If the internals become strong enough to not break, you simple start busting cases. Ask Kyle Michaels. He ran one in Climax at an estimated 1000rwhp+ and one grenaded on him and it was the super special (aka super expensive billet this and that) one from ProFab that is FULL TIME 4LO. Since then, I've asked ProFab about using one and was told "nope, we got nothing for the np205 behind a healthy diesel" (in a nutshell of course ).
Decent for gasers and crawling and mild power? You bet! Up for big power, 4wd boost launches, sled pulling, etc.? Not a chance!
C-ya
Now, with some of the beefy gears and some attention to the output shaft I'd say they will be alright in a tuning-only 500rwhp street type truck but it's well documented that they will not last behind a big torque diesel if pushed hard such as in the case of sled pulling or boosted 4wd launches. If the internals become strong enough to not break, you simple start busting cases. Ask Kyle Michaels. He ran one in Climax at an estimated 1000rwhp+ and one grenaded on him and it was the super special (aka super expensive billet this and that) one from ProFab that is FULL TIME 4LO. Since then, I've asked ProFab about using one and was told "nope, we got nothing for the np205 behind a healthy diesel" (in a nutshell of course ).Decent for gasers and crawling and mild power? You bet! Up for big power, 4wd boost launches, sled pulling, etc.? Not a chance!
C-ya
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Its very simple to do. My truck in my avatar started life as a 2x4. And i no you wont be as ruff as i am on the truck. You wont even need a dana 60 front you could put a dana 44 in it and be find as long as u dont go over a 35 inch tall tire. I havent had a problem yet with my hd dana 44 and i run 44 boggers. Need any help pm me
I think its just going to stay the way it is. I just bought an old BB dually and I have a S10 blazer to drive if it gets real bad in the winter.
Your trucks also a GMT400 with a 350 gas; not a heavy Duramax. Whole different ballgame as already metioned.
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How do you propose that would eliminate any need for electrical modifications? A signal will still have to go to the ECM/TCM to let them know when the truck has been engaged in 4wd so they can use the appropriate tables in the tuning for 4wd mode. If going to a remote transfer case, while it might not be 100% necessary to get the truck to function in 4LO without it, it'd be best (and not a jerry rigged setup) if you get the speed sensor POST transfer case just like it is in the gm800-900 trucks. Again, that way the computers know when to tell the transmission to shift properly.
The only thing electrical that would be eliminated that way is the ground wire that controls the actuator on the front IFS diff. which we've already discussed can be done easily or done away with entirely with a Posi Loc kit.
So, NO. I'm convinced that going SFA will actually be MORE work than converting his front 2wd IFS to 4wd IFS especially if you are talking about divorced np205 transfer cases. Doing the later (sfa w/ divorced 205) will require a LOT more fabrication just to mount the pieces and then have to retrofit electrical components to pieces that never had elec. components before. Anything is DO-ABLE though.
Now if he was willing to give up the alli in favor of a manual tranny, then I might give a little more lean towards SFA because then the hardest part would just be the mounting of the axle and xcase and it opens up some options on transfer cases depending on desired application of the truck. The ECM would never need to know if it was in 2wd or 4wd if it's a manual (although I'm thinking the manual tranny trucks DO still know when it's shifted into 4wd) and there is no TCM to speak of. The engine will run the same either way, and the man in the seat controls when and how it shifts; not a bunch of computers talking to each other coming up with what they think is the right time to shift based on too many sensors regardless of what the driver might be thinking is the right/ideal time.
C-ya
Mitch you have taught me something that i didnt no. But why does the truck have to know that it is in 4wd if its gear to gear case? When you but it in 4 low its the gears that do the swamping of the gear ratio aint i correct? Not trying to be rude i just understand it.
It puts the truck in a type of limp mode and limits the rpm. Had it happen to my puller before I added the pigtail to the harness to hook to the t-case sensor.
Is that the same with the standard trucks? They have to read the transfercase signal to work correct?
I don't know for sure but I'd guess so because the limp condition comes from a mismatched speed because the VSS signal is off due to being in 4wd. If you make it so it doesn't ever need a VSS signal, it might not limp it. Or maybe you could switch the tuning so it doesn't limp for that condition? There has to be some way to do that because the engines will run on an engine stand with no transmission and no VSS.
C-ya
C-ya
but shift timing will be screwed up that way on an auto... for a stick, just the speedo would be off in 4LO.
What do you mean by shift timing?but shift timing will be screwed up that way on an auto... for a stick, just the speedo would be off in 4LO.