4L60e won't shift right in 4 low, tune attached

I need some help! I have a race on Saturday and I can't get my jeep to shift right in 4 low. It works perfectly in 2 or 4 hi. The VSS is in the tailshaft of the NP205. I have a 2007 LQ4 that came out of a 4x4. I have changed the ratio from 2.72:1 to 1.96:1 for the NP205. I have wire 1694 wired through a grounded switch to tell the PCM it is in 4-low. I put the VSS in the tailshaft of the TC because this where GM put it.

Here is what it is doing. It shifts at 1/2 the RPM it is programmed for. It shifts good and hard, etc, just short shifts.

Other facts to note: I have a separate tune for running in 4-low because I don't want to use 1st gear. It is too low and wastes time. Much quicker to start in 2nd. I did this by zeroing all of the shift tables for 1st-2nd shift. Seems to work fine.

As a work around I have told the PCM it has an 80 tooth VSS ring and it works fantastic in 4-low. I know this is telling me something, I am not sure what??? I think it means the PCM isn't calculating the ratio change. I have read that 1694 is for nothing more than the light on the dash. True or no?

Attachment 52018

I now know why people put the VSS on the transmission tail shaft. Makes more sense because then it doesn't matter if you are in 2 hi or 4 low. The speed signal is still the same and therefore shift points work in either range. Please tell me I don't have to move it!

Can you change the shift points using the performance mode when in 4 lo? Or in our case tow/haul...

That way you just put it in tow/haul at the same time you engage 4 lo. or I believe there is another performance mode available in the transmission settings. I could be wrong about that. In my tune Transmission>General>performance option, mine is selected as class 2 (whatever that means) but there is an option for 1 switch or 2 switches. Maybe there is a way you can have it automatically put it in tow/haul at the same time the transfer case goes into 4 lo with a microswitch or something...

Might work...?

As for starting out in 2nd.. this is where I am probably completely wrong, but first a question. When you are racing do you ever need 4th gear? if not could you use a switch and disable your 1-2 shift solenoid?

That should start it in 2nd and then allow 3rd, but you won't have 4th either...

I do need 4th gear. Zeroing out all the values works really well it seems. It starts in second and works fine while in 4 low, with the exception of shifting at 1/2 the programmed RPM.

I would still like my regular driving tune to work right in 4-low for when I am at the off-road park, etc. I am baffled as to why when I flip the switch it doesn't scale the shift points correctly. If it works in a stock truck, it should work in my setup. I have only changed the ratio of the T-case from the factory setup.

Has anyone ever put their stock Chevy 4x4 in 4 low and floored it? Does a factory truck shift at the same RPM in 4 low as it does 2 hi? Or does it short shift also?

Factory truck will shift usually at higher rpms, but only because they climb so quickly and the transmission didn't grab the gear quick enough. Mine would bounce off the limiter before shifting, but it does shift...

I hate to say it, but I think you have the wrong wire grounded out and are not actually telling the computer you are in 4lo, either that or there is more than one wire... I would double check that first.

I thought that too so I ran the wire and it is the right one. When I turn it on and off it changes the shift points if I am in 2hi to be really quick because it is doubling the mph reading. I have pulled up the schematics and there is only one wire. 1694. I am sure I am missing something, but I see a lot of posts where people have the same issue and put it between the trans and transfer. I just think there is a way to make it work correctly, just don't know what I doing wrong. I will take your advice and look at the schematics again and check the switch for proper grounding, etc.

Is there two lights on the dash of a 2007? one for 4x4 and one for low range?

I think there is on mine, but it is a 2002. What year is the ecu? I am assuming this was a motor swap.

http://s150.photobucket.com/user/Poc.../blue.png.html

#34 blue connector? looks promising...

4low tables are available, e-mail support (aka BILL :) ) with an attached OS and request the 4LO tables (14998 and 14999 tables). I had them added to mine, and they work great. It appears that the WOT % trigger is the same for both normal and 4lo and he told me there are no 4l0 wot shift speeds, just 4lo normal shift speeds.
Attachment 52204

Ranger6202,

You are the man!! I was about to give up hope. Email has been sent to Bill.

Thanks!!

Hi Gup,

I was wondering if you got any response back? If so, can you share your tune? I am having the same issue. Even with the 4wd Low pin grounded to a switch, the tranny is not shifting when I put it in low.

Quote:

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Originally Posted by srobertsfsj

can you share your tune?

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Doesn't work like that. You need support to add the 4low tables to your specific OS. By chance if your OS Matches GUP or my OS, you'll already have them available on 2.25 as we requested them to be added to our OS's.
As for your particular issue, is the OS in your ecm for a 2wd or 4wd..... As that will matter also.

Gotcha, yes it is a 2wd tune. I am new to this so i wasnt sure. My scenario is that I have installed a 5.3l/4l60e/np241c (manual shift TC) into a Jeep Wagoneer. The engine came out of a 2001 Silverado 2WD. The person I bought the engine from said the PCM was flashed as a 2002 Tahoe but after scanning the PCM I found that it was still the 2WD OS. The setup runs great except for the lack of shifting in low range. I would prefer not to spend $300 on the AA kit to install the VSS in the tranny tailhousing so I was looking at other alternatives. I am fine manually activating the low using a dash switch but it doesnt seem to work so that brought me here.

The version of HPT I am using is 2.24 and I do not any updates on the website so I am not seeing them in the OS.

And I apologize, when I said share tune I just meant I wanted to look at it to see what the differences were so I know what specifically needs to be added.

Thanks!
Scott

Quote:

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Originally Posted by srobertsfsj

And I apologize, when I said share tune I just meant I wanted to look at it to see what the differences

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What I meant was that it wouldn't do you any good as you won't have the 4lo tables available on your OS.
Have you thought about adding a tow haul button and changing those tables to 4lo settings?

So would I be able to just flash an OS/bin from a 4wd or am I stuck with that OS? I realize it will cost me but that would be the easiest route.

I would strongly assume so. But i'm not 100% positive as i haven't had this issue being that all my swap projects have been 4wd OS's. You might want to write support with your OS attached and ask them if the 4l0 tables are even there. If not, then i'd find a 4wd OS. If so, then you'll at least have the tables added to your OS.

Srobertsfsj,

Believe me when I say I struggle through all of this. I think you can add the tables you need to make your 2wd ecm to work for a 4wd ecm, but I am not 100% sure. You may have to get a 4wd ECM. If it is possible, you do this by requesting V2.25beta from tech support. You can then copy and paste the 4WD tables you want from a 4wd tune...I think. That is what I did to change my ECM from 4L80e to 3L60e, along with a couple of wires changing. You will have to add a wire (1694 I think) to get your 4wd low signal to the ECM. The toggle switch can be mounted to your dash and it is a grounded signal. Then, once you have added the tables you need from a 4wd tune (from the repository), you can ask tech support to add the tables for 4wd low as they are not visible without doing this. Or you could ask for the tables to be added when you request V2.25 beta.
Now my 4wd low works perfectly and I can adjust shift points. I have a switch mounted on the dash to toggle when I am in 4 low.

Hi Gup,

Its funny you posted this because that is what I have been doing for the last few days. The HP Tuners support guys were nice enough to add the 4wd low tables and using the beta software I put in the settings similar to other files I have seen, but, it still doesnt work right :(

Here is the thing , I can get it to shift up. If i get the rpms over 3000 and then decelerate, then it shifts up for some reason, but it does this with the toggle switch off too. I wonder if that is some sort safeguard in the tranny? It seems to downshift just fine tho.

I am at a loss here. Maybe my toggle switch is bad or the PCM is bad, not likely but maybe??

I was really hoping I could get this PCM to work. I really dont want to have to buy another PCM and then pay for modifying it.


EDIT: I was curious about the toggle so I just went out and ran the wire straight to ground. No change.

I'm considering picking up HPT to solve a low range issue I'm having with my project ('98 GMC Savana, L31 with 0411 PCM, converted to 4WD). I have my NP205 set up with switches on the hi/low range and 2/4wd shift rails and am using a 241C VSS at the Tcase rear output shaft, with the 02' Express van tune in low range it won't shift out of 1st gear. The tuning software I have doesn't have access to 4WD low tables or transfer case ratio, but I can enable/disable the 4WD option. It sounds like from the above posts there is a version of HPT that can access the 4 low tables if you request that they be added to that 2.25 beta version of the software - am I understanding that correctly? - the info here is almost a year old - wondering if there have been some changes? I also read that there is access to a transfer case ratio but that altering that ratio just changes torque calcs that the PCM does and it doesn't change shift points in any way, correct?

All versions of HP can adjust those tables. If your OS doesn't have the tables, you are correct in requesting those tables to be added by support. You then update your Hp with the newest revision (updated daily in your customer center).