I am thinking about having my differential gears changed from 3.08 to 3.42 in my 2013 Yukon 4wd. First question will the gear change make a big difference for towing our 6000 lb boat? Right now the Yukon is very slow on hills and highway speeds while towing. Second question, has anyone done this before? If so what gears did you use? I was looking at Yukon gears, but a local shop that I talked to said they are not very good and tend to make gear noise. They recommended installing OEM gears in the rear and a aftermarket gear in the front. Any help or feedback would be much appreciated.
Differential gear change
- Thread starter Jeremy05
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swathdiver
Full Access Member
You might even consider 3.73s. I too would suggest OEM gears which are from American Axle and Machine, AAM. The lower gear (higher numerically) will help you get moving better and maintain higher highway speeds. With that much weight, with 3.42s, she'd turn about 3000 rpms at 70 mph in 4th gear with Tow/Haul activated.
Others with more experience will chime in soon.
Lancem
Member
I would go with 3.73, I noticed a big difference towing from my old 3.42 truck to my new 3.73 truck.
Would I notice a big loss in gas mileage if I went to the 3.73? What I have heard is that the 3.42 gears with the 6 speed transmission perform similar to the 3.73 did with the 4 speed. We will still do a lot of highway driving without the boat, so I don't was to give up to much MPG, but I also don't want to spend a lot of money on gears and not make a difference.
swathdiver
Full Access Member
Jeremy, my truck is tuned and has AFM turned off. I get 20 mpg @ 65 mph and 18 @ 70 mph. My truck has 3.42 gears and the 6-speed. The motor turns about 1775 rpms @ 70 in 6th. I talked to another guy with same setup as me the other day on Fuelly and he too gets 18-20 @ 65-70 mph.
What mileage does yours get now at those speeds? I reckon you're turning about 1600 rpms @ 70 mph. 3.73s would have it turning 1920 or thereabouts. Unless someone with direct knowledge chimes in, I think you can safely double whatever the difference in economy is between mine and yours to know how 3.73s would perform mileage wise.
But for towing that much weight, you'll not likely run it in 6th, 4th mostly and maybe 5th.
Ilikemtb999
Full Access Member
I had 3.73’s and a 6 speed in my Sierra. Granted it was a 6.0 but 6th gear was quite low cruising and got near 20mpg on the highway. The steeper 1st gear was nice compared to my old 5.3 4 speed truck with 3.73’s off the line.
If you’re going to the trouble of gear changes, I’d go 3.73 especially for towing.
If you’re going to the trouble of gear changes, I’d go 3.73 especially for towing.
I have a Black Bear tune on my truck and turned AFM off. Right now I know that I can get around 22 mpg on flat ground cruising at 60-65. At 70-75 mph I think that it drops down closer to 20 mpg. It does not take much of a hill to kick the truck out of 6th gear and the MPG goes down quick.
swathdiver
Full Access Member
Mine holds 6th and the converter stays locked up save for one tall bridge between our home and grandma's, over 60 miles each way. Not towing of course!
Have you talked to Nate? He's in the same boat as you:
https://www.tahoeyukonforum.com/threads/newbie-yukon-xl-owner.108719/#post-1295233
@NateDavis49686
My towing has been mostly city and low speeds and maybe hit 6000 once with this truck. Last month we did a run that put us on the highway coming back home and the truck would not go into 5th gear. I figure we were only pulling about 3,000-3,500 pounds tops but it was into the wind and the motor was on Ethanol. E85 makes more horsepower but the truck hummed along in 4th gear @ 3,000 rpms @ 70 mph. I thought she should have gone into 6th even with that light load but either the wind was worse than I thought or something else.
GM configured these 1500s to tow their max with 3.42 gear. You'll gain more towing prowess with 3.73s but lose a little more mileage. Like Nate, try it as is first and see how she does before throwing money at it. Well, save for the cooling system enhancements. Those will always pay dividends.
swathdiver
Full Access Member
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