4l60 vs 6l80

I owned a Tahoe for 8 years, it had 4.10 gears, drove great, very good power, towed great. In all my wisdom I though if I installed 3.42 gears it would get better MPG and I would like it better.

I found a complete 3.42 axle and swapped it in. Pulled my front drive shaft to avoid any issue with my 4x4 and drove it for 3 months.

I hated the 3.42. No doubt at 75-80 mph it was quieter and I liked that. All other aspects of the 4.11 were better. MPG was a wash, did not notice any difference but did not take a long trip with the 3.42 where it may have gained 1 mpg better.

We did a 1400 mile trip every year and had to go across Nevada and up through Idaho. On that one trip where we would hit Nevada and have 400 miles to the next turn off I wished I had the 3.42 so I could run 85 mph without turning 2800 RPM. With the 4.11 I held 78 MPH and got 17 MPG on those trips. Those trips were the only time I ever preferred the 3.42 gear ratio.

I sold that Tahoe and bought the Yukon in my profile picture. It was only 1 year newer but had 3.73 gears and only 75,000 miles on it and was a garage queen so looked brand new when I bought it. The 373 gears were a better combo, worked well in the city and would run 85 on that 1400 mile trip no problem. Still got 17 mpg. It was not a snappy as the 4.11 gears. Last year after 10 years ownership I sold the Yukon for a 2008 Yukon Denali with the 6.2L and 6L80, 3.42 gears which I wish were 3.73 so the tranny could stay in 6th gear on the highway at 65 mph. It shifts up and down all the time unless I am at 70 mph +. It would probably like 4.11 gears also but 3.73 would fix the 65 mph issue.

I only bought the 2008 Denali because I found it cheap with engine damage but a really good body and paint, zero rust, so I planned to fix it and sell it for profit but my wife thinks it rides and handles much better than out 2003 so we kept the 2008.

West 1 said:

I owned a Tahoe for 8 years, it had 4.10, drove great, very good power, towed great. In all my wisdom I thought,
if I installed 3.42, it would get better MpG and I'd like it better.
I found a complete 3.42 axle and swapped it in. Pulled my front drive shaft to avoid any issue with my 4x4 and drove it for 3 months.

I hated 3.42.

No doubt at 75-80 mph it was quieter and I liked that. All other aspects of 4.10 were better. MpG was a wash, did not notice any difference,
but did not take a long trip with 3.42, where it may have gained 1MpG better.

We did a 1400 mile trip every year and had to go across Nevada and up through Idaho. On that one trip where we would hit Nevada and have 400 miles to the next turn off,
I wished I had 3.42 so I could run 85MpHh without turning 2800RpM. With 4.10 I held 78MpH and got 17MpG on those trips.
Those trips were the only time I ever preferred 3.42.

I sold that Tahoe and bought the Yukon in my profile picture. It was only 1 year newer but it had 3.73 and only 75,000 miles on it and was a garage queen,
so looked brand new when I bought it. 3.73 were a better combo, worked well in the city and would run 85 on that 1400 mile trip no problem. Still got 17 mpg.
It was not as snappy as 4.10.

Click to expand...

I wonder how many people don't want to admit that their experiences are very similar to yours?
.

Was the 4.10 to 3.42 swap tuned? It sounds like that swap was a 4l60 with the taller 1st gear?
Without a tune it would be shifting at the same speed as before, but at lower RPM's..

NOT saying you wouldn't prefer the 3.73 all around anyway!
Just pointing out those variables that may make the taller gear seem worse than it is..
It sounds like the majority of issues people have with taller gears is freeway speeds..
(The only time *I* notice the shorter gear improvement with my 5.3, 6L80)

But in your case @West 1, regarding your '08, it sounds like a minor tweak would fix alot...
In fact, the '09 escalade seems to improve right there..
Downshift speed is up 15mph at 50% throttle (where yours is 60mph, '09 is 75mph) but only up 3mph at 56% (87-90mph)..
The '09 upshift is also raised @31-37% tps, so when it does downshift, it will not be so eager to upshift.

I imagine a Black Bear tune could dial it in to your needs even more..
Without OTHER nagging issues, it maybe overkill to swap gears in your '08 6l80?

'08 escalade below, assuming it's same as yukon denali..


'09 escalade

All of my trucks run the factory tune. With the new Luk Torque Converter the 08 Transmission seems to hold the lock up longer and I like it better.

Edit, I should have included one more rig I had for 3 years, a 2001 GMC Yukon Denali with the 6.0L and a 4L60. All bone stock. On the 1400 mile trip that rig was pretty great. Had to pay attention to keep the speed from creeping up over 100 MPH. It had 3.42 gears but the 6.0L pulled better than the 5.3L in the 2002 Tahoe with 3.42 gears. The 4L60 failed at 58,000 miles in the Denali. The 01 Denali would get 15.5 on the Idaho trip. Flat ground it drove great but in the hills the 6.0L 4L60 was not a perfect fit.
I think 3.73 would work better in that rig also.

I just meant if you updated the tune when you swapped rear axle.
GM 4.10 factory tune updated to GM 3.42 factory tune?

That is a significant change in ratio, plus the 4 speed.

Did not change anything, used the same program with both rear axles. With the 3.42 installed it ran and shifted fine. I did not try and race it but I did take it to Lake Tahoe which is 80 miles uphill. The tranny shifted as I would expect. No issue with the RPM at each shift. The seat of the pants performance, again not racing, just towing and driving was big between the 3.42 and the 4.11 in the 5.3 Tahoe with a 4L60 trans. It was like taking off in 2nd gear all the time compared to the 4.11.
If you are happy with a 3.42 powered Tahoe don't test drive a 4.11 powered Tahoe, it will spoil your thoughts.

No arguments here, just keeping track of details, thanks!

And although this thread started as a 4l60 vs 6l80...
I wonder if @gmartin1215 can comment on the 4.10 to 4.56 swap while we're at it?

I've had some more time to check out my new @BlackBearPerf tune on my ECM and TCM with the 4.10 gear set. I really like how the transmission keeps a gear that is in the lower torque band while cruising on class 2 and 3 highways, instead of trying to work its way to 6th gear as quickly as it can. It seems like I'm always only a light gas pedal touch away from acceleration when needed.

Lately I'm messing with my 5-2 and 6-3 downshift. Those two downshifts aren't direct, and go to neutral first, pausing a little before dropping into low gear hard. I'm guessing those two shifts are a big reason people say not to floor it from cruise.

Disabling neutral skip downshift feels better so far. FEELS like it goes 5-3 quickly, then 3-2 is the high torque shift, but smoother than leaving neutral skip down enabled so far. (I say feels because I have not logged it yet. I put my minimum 4-5 and 5-6 to tow mode speeds, so now it's harder to hit 5th around town)

Not sure the reason it is normally enabled. Neutral skip upshifts don't seem like an issue since your lifting throttle, low torque..

I have had a truck and a Tahoe 99-06 4l60 3.73 gear 4wd.
Both were 5.3
The truck got pretty good fuel mileage and towed pretty decent. Highway rpms for both vehicles were about the same 2000 depending on speed.

The Tahoe towed decent as well but got horrible mpg best I ever got was 15 all highway going across tx on i20.
It was flex fuel though and I assume the tuning for that was to blame.

Now I have the 07 Yukon 6.2 6l80 3.42 gears awd. I have not towed much with it yet just around 2k on a small trailer but it does better than any of the others now that I have replaced the torque converter with the luk and tuned the trans it is very nice and makes having 3.42 not so bad.

If I was towing a lot with it I would want the 3.73 gears and if I had bigger tires and towing I would probably want 4.10.

I had a few obs trucks with 3.42 gears and absolutely hated them. The 6l80 and the additional torque of the 6.2 really makes it nice

mikez71 said:

wonder if @gmartin1215 can comment on the 4.10 to 4.56 swap while we're at it?

Click to expand...

Until he responds, he had already said the following:

gmartin1215 said:

I got the work done to re-gear the truck to 4.56 ...
Driving around town, it definitely improves over 3.42, and gets to 5th and 6th sooner. At 75 MpH, I hit about 2300RpM when it reached 6th. I have not tried towing with it yet.

Click to expand...

What size tires is he running

Chris2144 said:

What size tires is @gmartin1215 running?

Click to expand...

285/75R17, 33.83" tall, 106.28" around.
GM OE tires are
265/70R17, 31.61" tall, 99.29" around, which partially explains why he chose 4.56 over 4.30.

Chris2144 said:

I had a few obs trucks with 3.42 gears and absolutely hated them. The 6l80 and the additional torque of the 6.2 really makes it nice

Click to expand...

Main reason I look at OBS trucks, but think 'I really want the 6 speed'..
Same when looking for an H2 hummer, only a couple later years have the 6l80 I believe..

mikez71 said:

Same when looking for an H2 hummer, only a couple later years have the 6L80 I believe.

Click to expand...

'03-'07: LQ4 6.0L, 4L65E, 315/70R17 (34.36" tall), 4.10 (should've been 4.30, check those tires again)
'08-'09: L92 6.2L, 6L80E, 315/70R17 (34.36" tall), 3.73 (should've been 4.10, check those tires again)

The 6 speed really is a huge improvement.
Makes having 3.42 gears not miserable.
But I will say the factory tuning is garbage.

Tuning mine made a big difference. A lot of factory tuning is not meant for performance.

Chris2144 said:

... the factory tuning is garbage.
Tuning mine made a big difference. A lot of factory tuning is not meant for performance.

Click to expand...

Axle gears are chosen, and GM OE shift schedules are programmed to favor CAFE MpG test scoring over real-world MpG expectations.

some of the feeling might be going from cable throttle to this fly by wire. cable always feels better to me, the gm electric throttle maping is always really weak. ford has more aggressive map to feel better with less tq.

also the gmt 800 is smaller and probably lighter than your bigger 900 suburban.


have the tranny tuned and drive it till the tc clutch debris causes a rebuild anyways

j91z28d1 said:

some of the feeling might be going from cable throttle to this fly by wire. cable always feels better to me, the gm electric throttle maping is always really weak.

Click to expand...

Did not think of that! Great point!
The throttle map 'defiantly' has a reduction curve under 50% tps or so..

mikez71 said:

Did not think of that! Great point!
The throttle map 'defiantly' has a reduction curve under 50% tps or so..

Click to expand...

my yukon isn't bad but it might be tuned differently because it's a hybrid and probably needs more throttle black opening with the weird cam and zero tq. but my c6 throttle sucks., I find I have to set the cruise on the interstate because without it as soon as I'm not paying attention I found have slowed down to like 50mph. the mapping requires what feels like 1/4 or more throttle to do 80 where the older ls1 cars with the cable, you just rest your foot on the gas enough to crack the throttle body and it feels like it wants to do a 100.

I wish hp would allow throttle map changes, but I've always heard you can brick the ecm by trying to adjust it. so everyone uses that silly throttle peddle piggy back things.