Anyone have experience with the 3.42 ratio Ring and Pinions?

[Billy Golightly]

I've seen a few aftermarket (Haisley Machine being one) and I see AAM offers them as well. My truck is an 03 with an NV5600 and I don't tow but once a year anymore, and its way light weight stuff. I think I'd benefit a lot in fuel mileage by going up to a taller ratio. Any thoughts or anyone with experience in changing a ring and pinion/going taller?

 

[HBarlow]

This subject comes up in various forms very frequently and the answers are generally the same.

If your truck will only be used for unloaded driving and occasional light towing you might gain two mpg with the 3. 42 gear set but if you calculate the cost of parts and labor to make the conversion and compare it to the savings of two mpg at your estimated annual mileage for the years you will probably own the truck I would guess that you won't save any actual money.

 

[Billy Golightly]

I tried searching for 3. 42 ring and pinion and 3. 42 aam and a few variations... I didn't get any hits back. Sorry for the repost?

Do you think 2mpg difference even changing from 4. 10's and not 3. 73's?

 

[DGamelin]

From 4. 10 to 3. 73 is about a 200-300rpm dereference not worth the time. I dont think you would see 2mpg. If you were going to do it, find the 3. 42. If your truck is a 4x4 a set of free spins hubs would be about the same as the 3. 73 gain. But a lot of $ like HBarlow says. You are going to have to keep the truck a long time to recoup your $.



_________________________

93 250 2wd xc 354 auto 174k

04. 5 3500 4wd qc dully 373 6speed 100k

 

[rscurtis]

You may never recoup your cost for some of these mods, I know I won't on some of the changes I've made on my truck, but you have the pleasure of making the vehicle perform the way you want it to and can always rationalize that you're reducing oil imports in the process.

 

[Turbo_Bob]

The sweet spot for our engines is between 1650 to 1950 RPM's. MPG will be the best at these speeds unloaded, which is 55 to 65 MPH. You have to figure out what speeds do you like to drive at and adjust your gear ratios to fit that parameter. Our trucks work good with the 3. 73 and 65 MPH of less. If you like to drive faster, 70+ then the 3. 42 would keep the RPM's in the sweet spot. But going faster you get aerodynamic drag, which will strip away any MPG from the taller gear.

 

[RWood]

I have the nv5600 and 3. 73 gearing. I am Interested in this switch because it would lower the rpms, in 5th gear at 55 mph, from 2175 to 1995. I do think this would show a increase in towing mpg. Also the manual transmissions were not designed to tow in over drive. Course I have 19. 5" rims and a swith to 35" from 33 will do about the same for less money.

 

[Turbo_Bob]

I have the nv5600 and 3. 73 gearing. I am Interested in this switch because it would lower the rpms, in 5th gear at 55 mph, from 2175 to 1995. I do think this would show a increase in towing mpg. Also the manual transmissions were not designed to tow in over drive. Course I have 19. 5" rims and a swith to 35" from 33 will do about the same for less money.

I have the stock 30" tires, 3. 73 R&P, NV5600, my RPM's in 5th at 55 are 2,300 RPM's, which works really good going up a 6% grade pulling 11,000 pounds.



I cannot leave it in 6th, not enough power, only at 1,675 RPM's at 55. This is where people get in trouble, chipping up the power, then towing in OD, both with the manual trans and the auto. On a level highway, less load on the powertrain it is not a problem to be in OD at a moderate speed.



Towing loads and going taller gear ratios or taller tires will not result in a better MPG for the most part. But I do think there might be some to gain if solo and not going too tall. The taller tire deal is probably the most economical way to go about it.



I figured out some numbers for comparison:



Baseline, 3. 73 R&P, NV5600

tire

30" 2,000 RPM 5th 48mph, 6th 66mph stock

32" 2,000 RPM 5th 51mph, 6th 70mph



Baseline, 3. 42 R&P, NV5600

tire

30" 2,000 RPM 5th 52mph, 6th 72mph

32" 2,000 RPM 5th 56mph, 6th 76mph



In my case pulling 11,000 pounds up a 6% grade at 55 mph in 5th gear, 2,300 rpm's, 3/4 throttle, max boost. Full throttle I can get up to 62 MPH.

If I were to use a 3. 42 OR use 32" dia tires, I would not get any better MPG towing, and in 5th gear at 55mph my RPM would be 2,100, I would be at full throttle, max boost and at max speed?



My own personal choice would be going the 32" 19. 5 wheel/tire combo. But I know I would have to use 5th gear much more often while towing.

 

[RWood]

I'm not saying there would be a huge gain. But I think there would be some gain by lowering rpms at the same speed. Just like I get better mpg in sixth than fifth. Evan . 5 mpg could mean a lot to towers. Not to mention the longevity of towing in fifth and not sixth.

 

[Turbo_Bob]

Course I have 19. 5" rims and a swith to 35" from 33 will do about the same for less money.

So right now you are using the 33", 19. 5 tire/wheel conversion ?



I was considering the 19. 5's a few years ago, but now in today's world, too many other things are on my plate to justify the expenditure.



There is another major difference between our two trucks, yours 325/610 vs mine 305/555 power outputs.

 

[RWood]

Yep. So far I really like the 19. 5". Better traction, better stability and hopefully longer life. I have the toyos but am going to try something else next time. I heard they can be retread for around $80 each, but have not verified it yet.