Axle 2.94 to 3.36 with TruTrac Installed

RBs Titan

New Member
Well fellas I just got back my truck from the shop. While there it got some new legs...yes my fellow Titaneers the whole 2.94 axle has been removed and replaced (swapped) with a 3.36 axle and Detroit/Eaton TruTrac pumpkin. Only 30 miles are on the truck since install and a 1/3 of that was done on the rollers and the reaming on the road by the installer. Sorry no pictures unless you want see the 2.94 axle in the bed of my truck. So no I have not done donuts yet but will have a video soon enough.



However I do promise to post my feeling based upon this mod and I'll do so in this thread. Also as I build data I’ll post it here. As you all know we have different ECU's for the trucks what remains to be seen is what will happen with the ECU codes, fuel mileage, drivability and of course drag strip.
 

MITitan

New Member
RB.. I've been doing some digging on being able to accomodate rear changes or wheel size changes and getting the speedometer back in line. Heck, if this works, we'll be able to get rid of the 4% error that many of us have with all factory components. If you are interested, shoot me a pm and we'll talk. It's something that will be totally custom, but readily available to those that want to do the work.



Mac.. I've got a 3.36 axle at the Nissan dealer with my name on it. Just waiting on Nissan Corporate to tell them what to do with it. If no response in 90 days (and we just crossed off #30), it goes in the dumpster (the back of my truck). From there, it's a transplant candidate for others.



I had the rear replaced as it was beginning to develop a bit of backlash... most likely the diff spiders. With a trutrac install those are out and this rear will be in great shape. It's only got 17,500 miles.



If you're intrested, let me know and we'll go from there.



Back on track here... I'm anxious to find out what things pop up with the ECU. I'm putting my money on nothing. I say that as the ecu does monitor wheel speed - but only in relation to each other, right? I don't believe it compares the wheel speed to the reported tranny speed.
 

QWIKWHIP

New Member
I think I have to agree that nothing will happen with the ECU. The wheel speed sensors are actually at the hubs, so a gear change will make no difference in the speedo. However, in the event that a hub sensor fails, it then takes it's info from the tranny speed sensor. So there is a slight possibility that they may conflict with each other?? Has anyone actually confirmed if there is in fact any different programing with a 3.36 or 2.92 trucks ECU? I'm waiting for a front and rear gear set to become available and then I'll be upgrading to the trutrac as well. I'm hoping for a 3.53 or 3.73 gear set for my 35's. <img src='http://www.titanspot.com/Titan/public/style_emoticons/<#EMO_DIR#>/002.gif' class='bbc_emoticon' alt=':smt003' />



So MI, what did you have in mind to correct the speedo for tire size? Fill me in brother. <img src='http://www.titanspot.com/Titan/public/style_emoticons/<#EMO_DIR#>/003.gif' class='bbc_emoticon' alt=':smt005' />
 

MITitan

New Member
Qwik... can you find me the literature in the service manual that actually says the wheel speed sensor(s) is/are used to calculate the speed?



The last time I worked on this, I thought it was the pulse sensor burried inside the tranny that was used. If it were to fail, there was a backup sensor (still in the tranny) that was used.



I'm re-studying the system now and I think I understand what I misunderstood last time. The TCM controls the tranny - shift points, lock up, etc. It does this based upon inputs (vehicle speed being one of them). This sensor is located in the transmission. Should it fail, the TCM will then look at the vehicle speed sensor MTR signal coming in over the Can bus from the combination meter.



This is good - I was under the impression that the changes we needed to make would be inside the pan - I really didn't want to go there but we need a solution for you fellas.



In RB's situation, I think his shift points may be off - he can confirm this by comparing against the charts in the service manual.



Update:

Well, I think things are worse now than before as the ABS system monitors all 4 wheel speed sensors directly - which in turn dumps the info into the can bus.... this truck is just too complex. I'll keep digging.



Thoughts: Can someone with the MiseryTom Burnout mod verify that if the front wheels aren't spinning that the speedometer does in fact go up with the excess rotation of the rear wheels - ie, the truck isn't moving but the speedometer says it is? If so, do the slip and abs lights come on. And if so, does it also do it with both back wheel spinning?



If this is the case, then the info from the back wheels seems to be a place to start. If not, we may be stuck.



I'm wondering if there is a "primary" wheel speed sensor that is monitored ie, right rear or left rear, etc. If this is the case, then the abs makes calculations based upon comparing the other 3 sensors to the "master". If I can find the master (if it does work this way), I may have a solution to "speedometer re-calculation".
 

QWIKWHIP

New Member
MI, I think your right. I looked it up and it does say the speed sensor is in the tranny. I got that information from somewhere else. Remember that solid axle titan conversion that guy did on TT a while ago. On his website, which is now down, <img src='http://www.titanspot.com/Titan/public/style_emoticons/<#EMO_DIR#>/012.gif' class='bbc_emoticon' alt=':smt012' /> He said he made new pick up "wheels" for the sensors on the hubs and that corrected his speedometer. So now I'm confused. lol <img src='http://www.titanspot.com/Titan/public/style_emoticons/<#EMO_DIR#>/017.gif' class='bbc_emoticon' alt=':smt017' />





Hmmm, maybe I am right???

http://www.clubtitan.org/forums/showpost.p...82&postcount=15
 

MITitan

New Member
lol... no need to go and get lost... it's all a matter of the flux capacitor and 1.21 Jigawatts - or a lightening bolt - which must be precisely calibrated to deliver 1.21 Jigawatts or how else do you get right back to where you started?



I think the speedo uses the wheel speed sensors - which feed the ABS - which CANs the info to the speedo, which in turn CANs it back to the TCM - but isn't used unless the tranny sensor fails.



So, to modify the speed of the vehicle, we'd need to modify all 4 of the wheelspeed sensors - I had a manufacturer in mind, but they responded with "ABS - not allowed to modify any signal feeding it as if there is any change or delay in wheelspeed signal from the wheels, it could be catestrophic - thus making it illegal to modify them" OK, that wasn't quoted, just paraphrased.



The same device I was thinking of doing this for would however work to change the shift points of the truck. You could use it to make the tranny shift sooner, or later, but as a group. We would just be fooling the tranny into thinking it's moving at a different speed - thus, changinging the shift points.



That being said, RB, if you'd prefer your truck to shift baed on the service manual table listed speeds (per speedo) and not where they are shifing now, I think you might be able to just disconnect the pickup sensor in the tranny pan......
 

steves

New Member
[quote name='MacLuvzDaVOLS']ok you guys have the wrench confused too ..... I do this for a livin and i'm lost......[/quote]

The jist of it is this: there are two sets of bits in the titan's transmission that are used to gauge speed, along with sensors at each wheel that transmit the speed of the wheel. The computer uses this information to shift the trans, and report the "speed" to the speedo.



They are talking about introducing new bits into the system to correct the speedo error/shifting error from tires/rear changes.
 

RBs Titan

New Member
Dealer Update

Ok took the truck into the dealer today. Just got a call back saying that the only fix there is for the cruise issue is to replace the ECU. However the catch is to replace the ECU with a 2004 4x2 BT no VDC.



They did say that the ECU could not compensate for the 8mph difference it is reading from the sensors. So for those of you wanting to go 4x4 with higher ratio you will lose your cruise control unless you can get big ars tires underneath. The good news is that the truck runs fine like it is just without cruise control of course.



So until someone comes out with some electronics tricks we are kinda of hosed on going down by the ECU.



MITitan - keep me posted on your findings...
 

RBs Titan

New Member
just wanted to update eveyone. The cruise is fixed and the truck is now programed as a BT. The ECU needed flashing and a few CAN codes deleted and there you have it. A perfect rear end swap from a 2.94 to 3.36.
 

Havock

New Member
[quote name='RB's Titan']just wanted to update eveyone. The cruise is fixed and the truck is now programed as a BT. The ECU needed flashing and a few CAN codes deleted and there you have it. A perfect rear end swap from a 2.94 to 3.36.[/quote]Sweet! I'm glad you are back in working order!



So Cypher hooked you up on this?
 
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