Swapping from 3.73 to 3.42 Gears

[trqmnstr]

What-if to your heart's content: http://www.klenger.net/dodge/general-reference/gear-speed-calculator.xls

Perfect! Thanks

 

[DerekW]

I might be wasting about 600 bucks, but I am going to try this. Haven't seen anyone at all do it, looks like I will be the guinea pig. If anyone has done it and I missed your post, please chime in.



I have a 2006 QC 2WD, short box Laramie, 27,000 miles, 48RE, 3. 73 limited slip.



I have acquired from AAM the part number for 3. 42 gears for my rear end. They hooked me up with a local distributor and they ordered them for me, about $450. 00 and $200 to install.



I have read a lot of posts about O/D units. This swap will save me 8. 3% on RPM's. That equates to the following:



MPH RPM 3. 73 gears RPM 3. 42 gears

60 1650 1500

65 1800 1650

70 1950 1800



I get 2 MPG increase in MPG slowing 5 MPH in speed. The 3. 42 gears will slow my engine about 150 RPM at 65MPH, which would be like driving 60 MPH. I am hoping to get 2 MPG increase driving 65, turning 1650 RPM, same as if I was driving 60 now. I might not net all the increase, but expect to get close to 2 MPG increase.



Here is the only worry I have... . I pull a 5000 pound enclosed car hauler occasionally, maybe 10% of the time, otherwise I am empty. I have pulled the trailer at 65 1800 RPM, and extended times at 60 1650 RPM and get about 2. 5 MPG better at 60.



These trucks have way plenty HP and torque. I can pull hills at 60 all day without ever unlocking the TC. That tells me that I should not be hurting my occasional towing capacity. I am smart enough to understand that I might be chopping a couple thousand max towing pounds off the top, but I never go there. My engine produces max torque at 1600 RPM and I will be a little above that at 65.



What do you guys think? I am OK with spending about 650 bucks for a solid 2 MPG increase for the life of my truck. I would not go any lower on the gears unless I NEVER towed.

WOW umm ok now yal are gonna think i am crazy but i WILL chime in on this. my dodge is over at NGM Diesel Right now 150 miles from home. I bought a $400 89 k5 blazer that needs new rings, and tune up cuz she spits and spudders, burns oil and blows it out the rear main under heavy load on 350 sbc. I been trying to get on my girlfriends parents good side after a rocky start. I ended up going to pick up a inop 98 tahoe that was located 50miles from there house. I drove 50 miles and burnt approx half tank of fuel. I loaded up and towed the inop off the farm in 4WL to take pressure off the transmission by using reduction post the transmission and build less heat since she is non lockup convertor. the wore out k5 was having a hard time going down the farmers driveway in 4wl and was smoking BADLY and sputtering cuz she was working herself to death. then i got on the road and decided to go a few miles in 4WL down the road since after she has auto locking hubs. then I ended up driving the whole 50 miles in 4WL on the dry pavement the whole way towing the tahoe. the first half of the trip I was going 35-40 then half way into the trip I started going 45MPH and cruised that way the rest of the way back to my girlfriends parents house. I did this in $WL for several reasons to take pressure off the transmission while towing well over what i was rate to pull, braking in 4WL was rediculously quick (let off gas to get in the brake and she already is bout stopped before your foot hits the brake pedal), my gf's dad didnt think it would make it in 4WL so i had to prove him wrong, i knew the internals of a chain drive t-case and had a spare t-case at house. GET THIS THOUGH SINCE YOU THINK I AM CRAZY AFTER WHAT YOU READ SO FAR. I ONLY burnt a hair less than a 1/4 tank of gas on the way home towing well over legal capacity at that. compared to the half tank i burnt driving all the way out there in 2WH with a tow dolly. sry I dont have a tach on the k5 to tell you the rpms but they were rpms with little load. if I had been towing that tahoe with the k5 in 2WH i would have had to stop about twice from burning and spraying all the oil out of the crankcase. not to mention overheating. oh and I had stock ratios of 3. 08 gears which suck for towing heavy and will eat trannies like no tommorow. OH and get this. the next day driving unloaded in 2WH stop and go she got hot then the upper radiator hose busted.



My buddy has a 86 chevy k10 pickup and he has 33's on his truck and had 3. 08s. when his rearend failed i towed his truck to my house and disobeyed his fathers request and did the right thing for his son and replaced the stock 3. 08s for 3. 73s and they are both happy cuz when the son gets fired and the father has to pay for the fuel he has noticed considerable drop in fuel expenses per week. I knew that needed to be done to help the both of them so i did it and they are glad.



My 04. 5 cummins dodge is going from 4. 10 to 4. 56 when she comes home from NGM Diesel. I know the cost savings to be had. you can guinea pig all you want this crazy 20 year old knows whats best for him.

 

[DerekW]

oh lets not even talk about my old 2004 jeep warngler with 6 cylinder 33's and 5. 13 gears riding around everywhere. they call for 4. 56 with 33's.

 

[DerekW]

Raychem, any advice on switching my 3. 73 to 4. 10? Can I just swap the ring/pinion? Also, do you know the cost of the gears and approximate cost of the labor? I would appreciate any info. Thanks Clay

since your a 2wd labor is only $250. R&P can cost you from 40 bucks good used to $140 new not from DC or AAM. but umm as for can you just swap the r&P and not have to swap carriers I wouldn't imagine on a rear end of this ring gear size, that the case break would be this numerically high, so I would say you will only need R&P, but I really am not sure where the case break is on the AAM 11-five. the original poster of this thread I would think is gonna run into the case change but like I said I dont kno exactly where the case break is on the ratio chart.

 

[DerekW]

Below is a post from another member with the part numbers. I do not think that they are making one right now for the 10. 5 axle, someone may in the future but that axle was only used for a short period of time. And my truck is a 4x2.















Richard

sir can you please post me the site you are getting your AAM P/N's i would like to see it for myself to look at all the optional gears for my 11. 5 and 9. 5 AAM axles assemblies. My local dealership needs a vin number to pull up parts and chevy's nor gm's come with gears any lower than 4. 10 on these axles that i am aware of. if you p/m me the site I will see it sooner. Thanks, Klinger.

 

[trqmnstr]

WOW umm ok now yal are gonna think i am crazy but i WILL chime in on this. my dodge is over at NGM Diesel Right now 150 miles from home. I bought a $400 89 k5 blazer that needs new rings, and tune up cuz she spits and spudders, burns oil and blows it out the rear main under heavy load on 350 sbc. I been trying to get on my girlfriends parents good side after a rocky start. I ended up going to pick up a inop 98 tahoe that was located 50miles from there house. I drove 50 miles and burnt approx half tank of fuel. I loaded up and towed the inop off the farm in 4WL to take pressure off the transmission by using reduction post the transmission and build less heat since she is non lockup convertor. the wore out k5 was having a hard time going down the farmers driveway in 4wl and was smoking BADLY and sputtering cuz she was working herself to death. then i got on the road and decided to go a few miles in 4WL down the road since after she has auto locking hubs. then I ended up driving the whole 50 miles in 4WL on the dry pavement the whole way towing the tahoe. the first half of the trip I was going 35-40 then half way into the trip I started going 45MPH and cruised that way the rest of the way back to my girlfriends parents house. I did this in $WL for several reasons to take pressure off the transmission while towing well over what i was rate to pull, braking in 4WL was rediculously quick (let off gas to get in the brake and she already is bout stopped before your foot hits the brake pedal), my gf's dad didnt think it would make it in 4WL so i had to prove him wrong, i knew the internals of a chain drive t-case and had a spare t-case at house. GET THIS THOUGH SINCE YOU THINK I AM CRAZY AFTER WHAT YOU READ SO FAR. I ONLY burnt a hair less than a 1/4 tank of gas on the way home towing well over legal capacity at that. compared to the half tank i burnt driving all the way out there in 2WH with a tow dolly. sry I dont have a tach on the k5 to tell you the rpms but they were rpms with little load. if I had been towing that tahoe with the k5 in 2WH i would have had to stop about twice from burning and spraying all the oil out of the crankcase. not to mention overheating. oh and I had stock ratios of 3. 08 gears which suck for towing heavy and will eat trannies like no tommorow. OH and get this. the next day driving unloaded in 2WH stop and go she got hot then the upper radiator hose busted.



My buddy has a 86 chevy k10 pickup and he has 33's on his truck and had 3. 08s. when his rearend failed i towed his truck to my house and disobeyed his fathers request and did the right thing for his son and replaced the stock 3. 08s for 3. 73s and they are both happy cuz when the son gets fired and the father has to pay for the fuel he has noticed considerable drop in fuel expenses per week. I knew that needed to be done to help the both of them so i did it and they are glad.



My 04. 5 cummins dodge is going from 4. 10 to 4. 56 when she comes home from NGM Diesel. I know the cost savings to be had. you can guinea pig all you want this crazy 20 year old knows whats best for him.

Wow!!! That was the most ramblist of rambles I have ever seen. I think that could have been summed up in about 3 sentences.

 

[NJones]

Maybe he was in a rambling mood.

 

[Morse]

OK. . Since the 3. 42's are now being shipped, who's going to be first to have them installed and give us a true result on our trucks. I was supposed to get a call when they started shipping out, though I haven't even called to see if I can get them now. . My truck is currently down getting a new combination. Who's first?

 

[Morse]

I just spoke to Greensburg Machine, and my 3. 42's are supposed to be here thursday or friday. Only bad thing is my twins won't be here for possibly two weeks and I sold my 62. .

 

[MLisle]

I have a 2007 4wd, so if i'm reading this right I can expect to pay $650. 00/axle ($1300. 00 total) for parts and labor. Might be time for a group buy and have a week-end gear change party. Anybody centrally located with a large garage and the special tools needed??? :-laf

 

[raychem]

sir can you please post me the site you are getting your AAM P/N's i would like to see it for myself to look at all the optional gears for my 11. 5 and 9. 5 AAM axles assemblies. My local dealership needs a vin number to pull up parts and chevy's nor gm's come with gears any lower than 4. 10 on these axles that i am aware of. if you p/m me the site I will see it sooner. Thanks, Klinger.

Those numbers were posted on page 4 or 5 of this post. Bill Laughman is my contact at AAM and he gave me all the current info and contact. Dealers in general dont know front from back and rarely help you without a vin unless the man or woman behind the counter know what their doing and that is rare!!! The numbers are valid... I have ordered every item on that list and have the install kits and rear r & p kits. . the front will be in fri or mon. American Axle makes various r & p gear sets from 3. xx to 5. xx. If you need and spec. info call me at 786-543-9176



Richard

 

[raychem]

OK. . Since the 3. 42's are now being shipped, who's going to be first to have them installed and give us a true result on our trucks. I was supposed to get a call when they started shipping out, though I haven't even called to see if I can get them now. . My truck is currently down getting a new combination. Who's first?

Friday if iI can get all my work done and do mine!



Richard

 

[Morse]

Raychem, I hope you get them in. .

 

[JChamberlain]

I just read this entire thread. This is what I deduce.

1. Auto equiped trucks turn 300-400 RPM slower than the G56 at cruising speed (75-80 MPH)

2. Just about every post I have read, in this and other threads, the autos are getting 2-4 MPG better mileage than the G56 equiped trucks

Conclusion: G56 equiped trucks WILL get better milage when changing to 3. 42 gears.





Questions?

 

[DerekW]

Maybe he was in a rambling mood.

always... jk

 

[Turbo_Bob]

Conclusion: G56 equiped trucks WILL get better milage when changing to 3. 42 gears.

I agree if solo, not towing. I think even the New Venture 6-speeds will benifit.

 

[Regcabguy]

Pay up!

I have a 2007 4wd, so if i'm reading this right I can expect to pay $650. 00/axle ($1300. 00 total) for parts and labor. Might be time for a group buy and have a week-end gear change party. Anybody centrally located with a large garage and the special tools needed??? :-laf

That's about what I paid for a ratio change in my '99. Fair pay for a hell of a lot of skilled work.

 

[WAnderstrom]

Anybody have some results from the gear change?

 

[raychem]

Put mine in today, let you know next wk. I have had them in the shop sitting for 3 wks. Customers first!



Richard

 

[Morse]

Any results yet? Mine are still sitting in the box. . My truck has been down for a couple weeks waiting on parts, and will probably be down atleast another week. I'm still curious as to how much they will benefit our trucks. .