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View Full Version : 3.42 rear end vs 3.73


mah2496
01-20-2008, 10:58 PM
I currently pull my PS205 with chevy 5.3L and 3.42 rear end. Does the 3.73 rear end have significant difference in towing ability and non-towing mileage vs the 3.42?

dmayer84
01-20-2008, 11:00 PM
I had an 07 silverado with the 3.42 and I traded it for an 07 sierra with the 3.73 and there is a huge difference. But mind you I had the 4.8 with the 3.42 and now have the 5.3 with the 3.73 and I feel like I could pull a lot more.

Cloaked
01-20-2008, 11:20 PM
I currently pull my PS205 with chevy 5.3L and 3.42 rear end. Does the 3.73 rear end have significant difference in towing ability and non-towing mileage vs the 3.42?Yes. The 3.73:1 will make a big difference in towing as well as it won't eat the farm with fuel consumption. I run a 3.73:1 in a GMC. It's the best gear GM offers for road use.

alletric
01-21-2008, 07:05 AM
I agree with the others. My wife has a Yukon with the 5.3, 3:42 and it does a good job towing don't get me wrong. I also have an 07 silverado with a 5.3 and a 3:73 and you don't have nearly the downshifts and reving. You hardly know that the boat is there.

bigmac
01-21-2008, 08:41 AM
Sierra 1500 with 3.42. I rarely tow the boat, but it hauls my wife's 7000# - plus horse trailer without any problem (3rd gear, tow/haul on). In the meantime, the vehicle get substantially better mileage than my previous trucks with 3.73 rear ends. I've only had trucks with 3.73 or 4.10 previously, so I was leery at first, but in the 2 years I've had the truck I've had no problems or complaints.

454Prostar190
01-21-2008, 11:54 AM
2007 Chevy with 3.42: Pulls the boat pretty good and yes, I use the transmission and the trailer tow/haul button as the power in the engine doesn't come on until about 2,500 to 3,000 RPM. I think that a 3.73 would be the way to go if I towed more but, the 3.42's and the 16 to 20 mpg for my everyday driving would be hard to give up. I live in SF and with the combination of freeway and the hills.... I average 15.5 mpg.

damaged442
01-21-2008, 12:13 PM
I have had three TrailBlazers that I've towed my boat with. This is my second with the 3.42. My first had the 3.73. The rated towing difference was 500 lbs more with the 3.73, IIRC. There was no noticeable difference. I saw a diff of 200-300 rpm at 60 mph, and the gas mileage was about 1-2 mpg lower with the 3.73. Granted, I'm only pulling a Tristar and she's not very heavy, but I think the 3.42s are OK.

sully
01-21-2008, 06:39 PM
We have a 4.8L & 3.73 which has been a good combination for low end torgue at the boat ramp and good gas mileage the rest of the time.
Average 18mpg hwy.

lanier92prostar
01-21-2008, 11:21 PM
I have had the 3.42 and the 3.73. The 3.42 is fine for towing smaller boats, plus you will get better gas mileage for everyday driving. If I were towing frequently on hilly roads, I might would go for the 3.73 for better gas mileage while towing, but the 3.42 should be fine with a 205.

Ric
01-22-2008, 08:34 AM
Yes, the 3.73 is the gear you want for an even balance between towing and round town non-towing.

I've worn out this subject on here and mac is the only person I've seen who likes the 5.3/3.42:1 combination from GM. I personally think it was a mistake for GM to offer this combo in a TRUCK. Pandering to grocery getters and mall runners.

Sodar
01-22-2008, 09:54 AM
Help me out on this one Ric...

I have an '05 Tahoe with a 4.8L and 3.42 gears. I flat out need some more gusto for pulling! I just put on a K&N and Magnaflow Cat-back Exhaust to help it breathe better and I am getting ready to send my ECM in for a "Hot Tune". Would I be smart to consider a 3.73 gear change before I have the tune done? I was just looking and I can get a gear set for about $200, plus install. What do you guys think? Am I pissing into the wind, or will it help out?

ShamrockIV
01-22-2008, 09:57 AM
man changing the gear will hurt ur MPG but hell go for it!! let me know how it does!!!

is urs 2x or 4x4 sodar? my yukon xl has plenty but it is a 4x4!!

Sodar
01-22-2008, 10:01 AM
Its 2wd. I could not see gas mileage being injured too bad, especially since I upped my wheel diameter by about 4"... to be honest, I think this is what hurt my performance.. with my stock wheels and tires, it seemed to pull fine.

ShamrockIV
01-22-2008, 10:05 AM
u may be right sodar!!! what are u running? 22's? 24's? they weigh a ton!!!!

Sodar
01-22-2008, 10:13 AM
u may be right sodar!!! what are u running? 22's? 24's? they weigh a ton!!!!

20's, but I upped my tire size to a 32" tire, to fill the gaps in the wheel wells, after I lowered it.

ShamrockIV
01-22-2008, 10:15 AM
sounds good sodar!! pm me i need to discuss the lowering with u!!

flipper
01-22-2008, 11:05 AM
Its 2wd. I could not see gas mileage being injured too bad, especially since I upped my wheel diameter by about 4"... to be honest, I think this is what hurt my performance.. with my stock wheels and tires, it seemed to pull fine.
I kind of did the same thing, but lifting with bigger wheels/tires. I changed the gears so the ratio would be the same as stock to the tires. Worked good for me. I still did the engine up a little just for fun, but didn't really need to with the new gears.

454Prostar190
01-22-2008, 11:07 AM
Sodar, You may consider a steeper gear ratio than a 3.73 with those big wheels. It would take some calculating but, I would almost bet that a 3.73 gear set will not take you back to the 3.42's that you started with. If you want some gear for towing, those big wheels are going to make things a bit different. I'm sure it looks totally cool though and cool is good! Rick

bigmac
01-22-2008, 11:08 AM
Yes, the 3.73 is the gear you want for an even balance between towing and round town non-towing.

I've worn out this subject on here and mac is the only person I've seen who likes the 5.3/3.42:1 combination from GM. I personally think it was a mistake for GM to offer this combo in a TRUCK. Pandering to grocery getters and mall runners.


and the horse trailer towers....

88 PS190
01-22-2008, 11:08 AM
You can always get 2 sets of gears and swap them out. Extra carrier will make it even easier as you won't need to remount the ring gear to swap.

That said hypoid oil and shimming can kinda blow.

Sodar
01-22-2008, 02:02 PM
Does anyone know of an online calculator that would help me figure a gear ratio out? If there are any math geniuses here, this is what I got.


Stock Tires were 265/70/R16

New Tires are 285/55/R20

Question of the day, what would gears would get me to a comprable 3.73 gear ratio with the new tires?

I had my old truck changed to 4.56's, but those were with 37's...

ShamrockIV
01-22-2008, 02:19 PM
You can always get 2 sets of gears and swap them out. Extra carrier will make it even easier as you won't need to remount the ring gear to swap.

That said hypoid oil and shimming can kinda blow.

swap gears????????
dang bro!!!! u got alot of free time or a pit crew at home???????

Ric
01-22-2008, 02:43 PM
Help me out on this one Ric...

I have an '05 Tahoe with a 4.8L and 3.42 gears. I flat out need some more gusto for pulling! I just put on a K&N and Magnaflow Cat-back Exhaust to help it breathe better and I am getting ready to send my ECM in for a "Hot Tune". Would I be smart to consider a 3.73 gear change before I have the tune done? I was just looking and I can get a gear set for about $200, plus install. What do you guys think? Am I pissing into the wind, or will it help out? You really need the 1500HD :D

88 PS190
01-22-2008, 02:44 PM
swap gears????????
dang bro!!!! u got alot of free time or a pit crew at home???????

I'm most used to the 12 bolt chevy rear end, which isn't that difficult to work on once you get used to it, the hardest part is determining the shimming, which if you have set it up and kept notes you can place the correct shims in place and eliminate the process.

Ric
01-22-2008, 02:45 PM
and the horse trailer towers.... slow pokes 8p

Sodar
01-22-2008, 02:53 PM
You really need the 1500HD :D

I want this... but it is not white :(

2005 Chevy Silverado 2500HD 4x4 6.6L Duramax Diesel w/ Allison 5 speed auto 60,000 miles. Diablo Sport Predator programmer, cold air intake, 4" Banks turbo back exhaust, 6" CST lift, Uniball upper A-arms, heavy duty tie-rods, 35" Nitto Terra Grapplers on 18 Chrome Wheels, lifted rear Deaver Springs, KING 2.5 Remote Reservoir shocks on custom shock hoops, HUGE Stereo, Head Unit feeding 2 amps, JL500 feeding two JL 12" subs, 4-channel Rockford Fosgate amp feeding MB Quart 6.5" components in the doors. Overhead 10" flip down monitor. Pager alarm with remote start. Too many other custom pieces to even list. This is a perfect truck, built with all the best parts. Drives and tows like a dream.
$29,999 obo.
Attached Images

30990

30991

http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4526&stc=1&d=120060510 4 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4526&stc=1&d=1200605104) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4527&stc=1&d=120060510 4 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4527&stc=1&d=1200605104) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4528&stc=1&d=120060641 2 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4528&stc=1&d=1200606412) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4529&stc=1&d=120060644 2 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4529&stc=1&d=1200606442) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4530&stc=1&d=120060644 9 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4530&stc=1&d=1200606449)

jraben8
01-22-2008, 02:55 PM
We can't see them unless we register.

Sodar
01-22-2008, 03:00 PM
Sorry... Fixed.

ShamrockIV
01-22-2008, 03:04 PM
sweet sodar they seel them with lift from the factory now!!! but they are PROUD of them!!!!

Sodar
01-22-2008, 03:13 PM
OK.... my mind drifted off into no-man's land. I cannot think about a new truck cause I gave MC all my money last year! :D

Anyways... I just spoke to a guy that is selling 3.90 gears for $125. That is too tall, don't you guys thing?

TMCNo1
01-22-2008, 05:35 PM
Does anyone know of an online calculator that would help me figure a gear ratio out? If there are any math geniuses here, this is what I got.


Stock Tires were 265/70/R16

New Tires are 285/55/R20

Question of the day, what would gears would get me to a comprable 3.73 gear ratio with the new tires?

I had my old truck changed to 4.56's, but those were with 37's...


IIRC as a (ballpark) general rule, find the published tire diameter or (off the ground/no weight) measured tire diameters for the OEM and aftermarket tire, subtract the OEM tire size from the new larger tire size, figure the percentage of the increased tire diameter over the OEM tire and decrease the OEM gear ratio by that percent for a ballpark rearend gear ratio. It will be close enough for government work!

Ric
01-22-2008, 05:55 PM
Thirty thousand dollars for a 2005 with 60thousand miles...... I must be getting old because that just sounds dumb


I want this... but it is not white :(

2005 Chevy Silverado 2500HD 4x4 6.6L Duramax Diesel w/ Allison 5 speed auto 60,000 miles. Diablo Sport Predator programmer, cold air intake, 4" Banks turbo back exhaust, 6" CST lift, Uniball upper A-arms, heavy duty tie-rods, 35" Nitto Terra Grapplers on 18 Chrome Wheels, lifted rear Deaver Springs, KING 2.5 Remote Reservoir shocks on custom shock hoops, HUGE Stereo, Head Unit feeding 2 amps, JL500 feeding two JL 12" subs, 4-channel Rockford Fosgate amp feeding MB Quart 6.5" components in the doors. Overhead 10" flip down monitor. Pager alarm with remote start. Too many other custom pieces to even list. This is a perfect truck, built with all the best parts. Drives and tows like a dream.
$29,999 obo.
Attached Images

30990

30991

http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4526&stc=1&d=120060510 4 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4526&stc=1&d=1200605104) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4527&stc=1&d=120060510 4 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4527&stc=1&d=1200605104) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4528&stc=1&d=120060641 2 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4528&stc=1&d=1200606412) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4529&stc=1&d=120060644 2 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4529&stc=1&d=1200606442) http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4530&stc=1&d=120060644 9 (http://www.riverdavesplace.com/forums/attachment.php?attachmentid=4530&stc=1&d=1200606449)

BrianM
01-22-2008, 06:32 PM
OK.... my mind drifted off into no-man's land. I cannot think about a new truck cause I gave MC all my money last year! :D

Anyways... I just spoke to a guy that is selling 3.90 gears for $125. That is too tall, don't you guys thing?
Those would be great in your Hoe. I am actually a big fan of the 4.10s. They are great for towing and add some pep off of the line. In a Hoe you are not going to notice any difference in the fuel economy. 3.90s would be sweet. Right in between the 3.73 and the 4.10. Good choice I would say.

BrianM
01-22-2008, 06:34 PM
Oh and here is a gear ratio calculator for you.

http://www.dirtroadmagazine.com/gears.htm

and one more

http://www.tyres1.com/tech_calcs.html

Sodar
01-22-2008, 07:23 PM
Those would be great in your Hoe. I am actually a big fan of the 4.10s. They are great for towing and add some pep off of the line. In a How you are not going to notice any difference in the fuel economy. 3.90s would be sweet. Right in between the 3.73 and the 4.10. Good choice I would say.

Thanks Brian. So were you being a bit sarcastic, or do you think I will see a huge decline in fuel consumption?

BrianM
01-22-2008, 08:23 PM
Thanks Brian. So were you being a bit sarcastic, or do you think I will see a huge decline in fuel consumption?

I am being serious. You will not notice much if any difference in the fuel economy. I used to sell GM and know from talking to customers that there is little to no real world fuel economy difference between the 3.56, 3.73 and the 4.10.

Sodar
01-22-2008, 09:08 PM
I am being serious. You will not notice much if any difference in the fuel economy. I used to sell GM and know from talking to customers that there is little to no real world fuel economy difference between the 3.56, 3.73 and the 4.10.

Cool! Good to know! I am going to keep looking and see what I can find!

mah2496
02-24-2008, 03:28 PM
Sounds like 3.73 is the rear end of choice. Anyone ever has their rear end swapped out?

TMCNo1
02-24-2008, 03:40 PM
Sounds like 3.73 is the rear end of choice. Anyone ever has their rear end swapped out?

In 1978, I ordered a new Chev, Stepside Pickup and in 1979, I had the 3:08 rear ring gear and pinion taken out and replaced with a 3:73 and positraction unit for $380 plus $150 labor by my local mechanic, but that was many years ago. I bought the truck for work and good mileage, then bought a boat that it didn't tow well with the 3:08, poor mileage and kept fouling spark plugs. It was about a 2 hour job and I sold the truck 8 years later with 100,000 miles on it, never looked back and had no problems with the swap out.

TMCNo1
02-24-2008, 03:46 PM
Yes, the 3.73 is the gear you want for an even balance between towing and round town non-towing.

I've worn out this subject on here and mac is the only person I've seen who likes the 5.3/3.42:1 combination from GM. I personally think it was a mistake for GM to offer this combo in a TRUCK. Pandering to grocery getters and mall runners.

Our '88 Chevrolet Astro Van has a 3:73 Positraction, 4.3 Liter V6 and has a 15.6 mpg average for towing the '89 PS190 over 30,000 miles, 21mpg without the boat on long trips, 18mpg around town, all on regular gas and the occasional bottle of STP Fuel Injection Cleaner. Yes, I keep records!

capnkirk52
02-25-2008, 03:39 PM
Don't fear the gear, especially if you are gonna tow with it. 4.10's would be perfect. I wouldn't send your ECM in either, just get a programmer and do it yourself. You'll be able to calibrate your speedo for the gear swap with that as well.

check out
www.rpmoutlet.com

click on your application and get a diablosport programmer. Lots easier.

flipper
02-25-2008, 03:45 PM
I have the 3.42 in my 2007 Yukon, and wish I had went the higher gear. I think I'm going to do the swap too.

mah2496
02-25-2008, 06:29 PM
Kirk -- does the swap require any mods to the tranny?