Axle ratio change for towing

[NVEli]

Hi, I have a 21 NV 2500 with the 4.0 V6, 5speed auto, 3.36 axle. The 4th and 5th gear lockout make towing less than ideal and 3rd is to low on the hi-way. Will a higher axle ratio help and what is available if so? Also would the 7 speed auto bolt up to the V6 and would that help? Thanks

[Local Apparent Friday]

You would go lower gear ratio for towing, not higher, but it's a moot point as nothing is avaliable aftermarket.  Best you can do is swap for the v8 ring gear which i think is possible and a different ratio, but my mind isn't in it right now. 

 

Theoretically the actual bolting of the two things together is no big deal. Trying to get it to run is a whole 'nother story.

[crusty]

Not a chance of the 7-speed bolting up.  The back of the block is completely different.  And the programming of the transmission is completely wrong as well. 

The V6 is OK in a mid sized truck.  Not really a good choice in a full size van that is trying to tow.  It can move it, just not a great job of doing it as you have found.

[crusty]

On 12/5/2024 at 10:36 AM, Local Apparent Friday said:

You would go lower gear ratio for towing, not higher, but it's a moot point as nothing is avaliable aftermarket.  Best you can do is swap for the v8 ring gear which i think is possible and a different ratio, but my mind isn't in it right now. 

 

Theoretically the actual bolting of the two things together is no big deal. Trying to get it to run is a whole 'nother story.

Correct, mostly.  The early V8 did have the 3.54 ratio.  Once the V8 got the 7-speed they all got the 3.36.

Go aback in history when the Titan was launched with this 5-speed transmission.  Nissan claimed the 3.36 ratio was like others 4.10 ratio.  The logic/math was the 5-speed had a much lower 1st gear.  So the standing start was very close.  But the Nissan 5-speed overdrive ratio was also very different as well.  The normal 4-speed transmissions that were out at the time had 0.70-0.75 overdrive.  While the Nissan had only .85 overdrive.  If you wanted to play even more, the Titan XD diesel has a 3.92 ratio in the same axle design that can be swapped into the Van's axle.  Or a 4.09 in the '20-24 Titan XD with the 9-speed (has a really tall set of overdrive ratios).

 

Nothing wrong with running in 3rd gear.  The VQ motor likes some RPM.  It has an oil cooler.  The basic engine design goes back to the mid 90s.  Versions of this engine are used in Z-cars, an alphabet soup infinity cars, well regarded in the engine design.  Trying to change the axle ratio is going to still put the engine into the same RPM band, just in a different gear, and make driving without the trailer much worse.