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Discussion Starter #1 (Edited)
Installed: Axle Swap 2.94 to 3.36 and TruTrac

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 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.
 

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C'mon Shift_Juiced put some pics up of that 2.94 in the bed of your truck !!!
 

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What are you going to do about the speedometer?
 

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Where does the Titan read it's speed from? Wheel rotation.....or the rotation of the transmission?? Or from another source?
 

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The primary speed signal is from a sensor that reads the teeth on the parking lock gear in the transmission. If this sensor fails it uses the wheel rotation sensors as a backup. The speedometer can't be recalibrated by the dealer. The instrument cluster must be sent back to the factory to be recalibrated.
 

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So it is now possible for the system to read two different speeds and give a error code I imagine.

Hope all works well. But his spedo is going to be off a nice amount.
 

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Discussion Starter #9
Wow responses already....and several...

Hmmmm well here are some pics of parts.

Also just for kicks and giggles I drove home with a pair of OEM 17's @ 29" tall on the 2.94 rear end this Sunday and the odometer was dead on with mile markers.

I check the speedo in the next few days. My biggest problem now is finding a buddy to move this massive bed weight and where the heck to put it.
 

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So did you buy an axle from a dismantler or something or did you find somewhere to buy the gears? How much did the gears/axle (which ever you did) set you back?
 

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He bought the axle assembly from another CT member, and used the 3.36 gears from it.
 

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Discussion Starter #12
I bought the complete used axle and used that complete axle and gears with a new trutrac pumpkin.

SCR...I just got back from driving to katy the GPS says speedo is very accurate within .5-1mph at all speeds.

Guys with BT what rpm are you getting at 70mph less/more than 2K?

This rear end with installation and total parts was $1100. I had it rebuilt new bearings seals etc as I had no idea of how many miles were on it.
 

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Keep us posted with info please.
 

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scr38 said:
The primary speed signal is from a sensor that reads the teeth on the parking lock gear in the transmission. If this sensor fails it uses the wheel rotation sensors as a backup. The speedometer can't be recalibrated by the dealer. The instrument cluster must be sent back to the factory to be recalibrated.
I thought it was the exact opposite of that? I thought it gets it's signal from the hub sensors with the tranny as the back up? And after hereing that his speedo is right on, that must be the case???
 

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QWIKWHIP said:
I thought it was the exact opposite of that? I thought it gets it's signal from the hub sensors with the tranny as the back up? And after hereing that his speedo is right on, that must be the case???
You are probably right. RB's test confirms that. The attached info from the service manual is why I thought it was the other way around. However if you look in the instruments section it infers that the signal comes from the ABS system.

Edit:
Added attachment from Instrument section
 

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Discussion Starter #16
After driving into work this morning (10miles) and driving it very late last night on the highway (15miles) I have a few comments.

1. The drone with my banks is now been displaced so now I can cruise at 70mph and not be bothered. yeeeeeeaaaaah! Wife was starting to complain.

2. My standard acceleration from stop (applying gas to keep rpm at 2K) has shifted to about 21-2200 rather than 18-2K during the gear shifting on accel.

3. Also the truck seems to shift quicker and stay in the power but I dare not say for sure until I get the Cipher on it and the old one removed from the bed of the truck.

With regards to the trutrac you know it's there when you turn in a tight circle other than that if I wanted to be extremely picky I would say that I can feel it grab during deceleration ever so slightly like a small surge. It's smooth, quiet and very driveable in the city/highway.

I used the Nissan Alum-diffcover and Nissan synthetic 75/140 oil.
 

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RB... as our truck's tranny monitors a gear in the transmission in order to determine the shift points, I'd say your thoughts of it shifting sooner are right in line.

The wheelspeed sensors could care less what gear ratio the rear end is and they just report how fast they are turning to the ABS which in turn dumps it into the CAN which in turn ends up at the speedometer.

The tranny on the other hand will only pay attention to the speedometer if the sensor in the tranny fails. So if it doesn't fail, the tranny will continue to shift based on how fast the tranny is turning over. If the rear end gear ratio goes up, the tranny will shift sooner as it thinks it's going faster than it really is.
 

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Discussion Starter #18
Rear Axle Weight

For those wanting to know weight of rear axle 2.94 OEM:
205 lbs. (no rotors or cables)
 

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Discussion Starter #19
Initial Data tests

Initial tests with Cipher as timer say:

The Good:
0-60 is .51 to .65 better with 3.36 gear.
My run from 75-110 last night did not cut fuel at top end. That's right I can hold 108mph. The truck shut down the accelerator voltage much like the cruise does and it limited air intake by cutting throttle body volts as well. This I could not do before with a smooth running engine and it actually surprised me.

The Unexpected:
Not sure yet if it's related to the gear change or the burnout mod switch that was posted as "busted"....but my cruise does not work. I used the burn out mod the first time at the track last Sunday and drove home with the cruise on that night. I did have 17" and 29"tall tires on the rear during that drive to get an idea of what the 3.36 might be like to drive.

The "SET" light blinks fast when turning the on/off button on. I can reset by turning ignition key off and waiting 10secs but as soon as I hit 40mph the cruise disengages and the light blinks regardless if I have tried to set the speed or not.

So I have another puzzle piece for the puzzle...I like challenges.
 

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I wonder if you've experienced maybe the one time the tranny compares the tranny's measured speed to the reported speed from the CAN line per the Speedo?

If so, you might be in a pickle.

Yep, per digging through the service manual, I found the following:




I'll bet you are pulling a malfunction code from the ASCD control when the wheelspeed and tranny speed don't jive!

If this is true, I think you can get your cruise working again, but it will require dropping the tranny pan to disconnect the powertrain revolution sensor from the TCM. Not fun! Then and only then will you find out if the cruise will work with the tranny speed sensor disconnected as I'm sure that will throw some sort of malfunction code as well.
 
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