4l60 vs 6l80

[Bronson357]

Ok so I have 2 gmt800 both with 4.10 gears and 5.3,also an 07 tahoe 5.3 all of these have a 4l60e. Then a 2012 5.3 with the 6l80 I don't drive this much but took out for a 60 mile trip at 70mph mostly interstate,cruise set and this thing is a dog ,constantly shifting, with cruise set at 70 it would down to 65 then shift down 2 gears and speed up. Rinse and repeat. Plus 1st gear is useless unless I punch it,normal driving it shifts from 1st to 2nd at like 7mph then dogs unless I kick it back down.

Are there any fixes for the shift points or 3.08 suck with the 6l80 the rear gear should be close to a 4l60e and 3.42?

Honestly it's 4wd so I don't want to get in to gear changes, it is basically a suzi soccer mom burb. I still think it should have some pep and it truly feel like the shift points are awkward.

Thanks

 

[Marky Dissod]

I have ... a 2012 5.3L with a 6L80 & 3.08. I don't drive this much but took out for a 60 mile trip at 70MpH mostly interstate, cruise set and this thing is a dog, constantly shifting, with cruise set at 70MpH it would bog down to 65MpH, then shift down 2 gears and speed up. Rinse and repeat.
Plus 1st gear is useless unless I punch it, normal driving it shifts from 1st to 2nd at like 7MpH, then bogs unless I kick it back down.

You're complaining about how the 6L80E's tcm was programmed by GM OE to behave.
It always tries to delay / discourage / avoid downshifts, especially to 1st if at all possible (except for WOT).

3.08 axle gear makes all the above that much worse. Blame GM OE & CAFE MpG test score bullschidt for that too.
Every GM truck with a 4L60E should've come with 3.73 or 4.10. Every GM suv with a 6L80E should've come with 3.42 or 3.73. Transmissions would've lasted longer.

Are there any fixes for the shift points? or 3.08 suck with 6L80E the rear gear should be close to a 4L60E & 3.42?

4L60E & 3.42: . . . . . . 10.47 . . . . . 5.57 . . . . . . . 3.42 . . . . . . . . 2.39
6L80E & 3.08: . . 12.41 . . . . 7.28 . . . . 4.72 . . . . 3.55 . . . . 2.62 . . . . 2.06
Clearly your 6L80E's last gear is not enough to cruise @ 70MpH, which calls for a downshift (if not a double-downshift?).
Once you've moved off of the redlight/stopsign, your 6L80E will try to avoid its 1st gear til it stops again; kinda like it wishes it were a 5speed?
4L60E & 3.73: . . . . 11.41 . . . . . . 6.08 . . . . . . . 3.73 . . . . . 2.61
6L80E & 3.42: 13.78 . . . . 8.08 . . . . 5.24 . . . . 3.94 . . . . 2.91 . . . . 2.29

Honestly it's 4wd so I don't want to get in to gear changes, it is basically a suzi soccer mom burb.

3.42 would help the 6L80E quite a bit - it's the GM OE Tow Pack gear, by the way. Note that tow ratings improve as axle gear improves, for a very good reason.
Does suzi's soccamamabile, REALLY need 4WD?

I still think it should have some pep; it truly feels like the shift points are awkward.

GM OE cares less about what you think than it cares about what CAFE MpG scores think -
otherwise every GM suv with a 6L80E would have 3.42 or 3.73. (4.10 is for REALLY Heavy Duties, 4.30 is for oversize tires.)
If you want to do something about the awkward shift points, and you are unwilling or unable to to do anything about the axle gears,
the only sensible option left is to get your tcm tuned.
Clearly, the tune should make it more willing to downshift with less provocation, among many other things ...

 

[Marky Dissod]

Forgot to say: you've 3 vehicles with a 4L60E. If one of them has a 3.42 or 3.73 rear axle, you ought to seriously consider putting it under her bubba with the 6L80.
Metro/urban city MpG will improve, highway MpG will stay pretty close, and the 6L80E will last longer even if you don't bother to tune it,
just because it will not need to downshift nearly as often. Think about it.

 

[mikez71]

3.08 isn't bad with the proper tune, going to 3.42 was underwhelming to me.
If you change ratio's, you will still want a transmission tune.
Transmission tune alone will solve your problem.

Don't engage 5&6 until higher speeds.
Bumping your downshift speeds will fix the lazy feeling. (31%-62% tps range)

 

[Prospect62]

My 2012 with the 6L80 was awful with it's 3.08's. I owned the truck for precisely three months before I absolutely had to do something, so I spent a good chunk of change on a DiabLEW tune. So far, the tune has worked wonders and the truck is actually pleasant to drive now. It's not quick or fast but it's tolerable. Before, it was as you describe yours - doggish, slow and always hunting for a better gear when it wasn't immediately trying to get into 6th. Now I feel like the truck has an easier time in almost all conditions and I feel like I'm saving my poor transmission's life.

As others have pointed out, the 3.08's and the OEM GM tune kill these trucks.

I owned a 2016 Suburban which had 3.42's and obviously quite a bit more power in it's 5.3 than this 2012 and it was faster and more fun to drive than this Tahoe in every way - even being much heavier.

Gears and a tune are the ultimate solution for modern V8 American trucks and cars (outside of forced induction, which isn't really practical). Gears on a 4x4 are a pricey proposition, though. Look into a good tune from DiabLEW or Blackbear. I am very happy with my decision to use Diablew's services. He has been great to work with.

 

[mikez71]

The 2016 tune is different than 10-14 tunes.
Just so you know, not completely apples to apples regarding what you are feeling vs gear ratios.
See shift schedule comparisons below. (2016 same as 2015)

'12, '15, '17 Tahoe 6l80 3.08 shift schedule comparisons.

had to tweak some 0% 2-1 downshift and 100% 3-4 shift to get the graphs to be on the same scale. So one number in each graph is wrong the lighter cells (8.14, 97.29, 97.29) The actual number is in the neighboring cell.(8.28, 95.94, 95.01) 2012 2015 2017

www.tahoeyukonforum.com

 

[Foggy]

Get Transmission Tuned for sure. Stock form I disliked the 6L80 with 3.42 and 6.2L..
So I bet 5.3L with 3.08 really Sucks !!!
HP Tuners lets you change all sorts of stuff in the trans tune to make it a very
enjoyable experience....
IDK where you live, but many people could do a quick change for you (including me) if you were local.
I love my 6L80 since I did the changes that suited me

 

[Bronson357]

I have read nothing but good about the trans, no suzi doesn't need 4wd but it's there and I'm not going to remove it either. Which kinda negates a gear change unless need but maybe. Compared to my other 3 this thing is slow unless you constantly hammer the throttle. And in theory it should get better fuel mileage than the rest. It does not but that's OK. I live rural and maybe if I was on flat highway doing 80 all the time???
I hate the cruise fluctuations and plain slow! Unless I nail it is goes fine!
My gmt 800s both have 4.10 and I have to be careful about throttle out of the driveway.
By my lazy calculations a 6l80 with 3.08 should be similar to 3.42 wise except double overdrive??
Trans does not get hot but is constantly shifting.

Thanks

 

[mikez71]

A tune will completely fix what GM screwed up.
I normally don't even feel my 5-4 downshift!
( very close to '17-'20 tune for 4-5 and 5-4, w/3.42 )

Mileage will still suck... I think mine went down a little.
Partly because I unlocked the tcc in 2 & 3...
But also because I'm less shy on the throttle.
( Since it will actually downshift now! AND feel smoother doing it. )

I used to rarely pass in heavy traffic, it just felt too laborious.
Cars kept cutting in front, I'd have to slow.. Before long everyone was in front if me!
No more resistance to acceleration, you will use a little more gas in all likelihood.

Downshifting at 37-50% throttle feels much better than downshifting @ 80+% throttle.
Sooner, smoother, and without the drama!.
Other tweaks make it shift quicker & smoother.
( torque adders and inertia factor are worth tweaking )

Everything applies to my daily driver tune..
No excessive RPM's, no harsh shifts, no TCC bump.

 

[Marky Dissod]

I have read nothing but good about the 6L80, no suzi doesn't need 4wd, but it's there and I'm not going to remove it either,
which kinda negates a gear change unless need ... but maybe ...

Feel free to pretend I'm NOT the wee lil homonculus on your shoulder whispering suggestions to consider how suzi does not need 4wd ...
It would lose weight, which would improve MpGs right there.
Then if you improve the axle gear to 3.73 or 4.10 (depending on how & where it's driven), the MpGs may improve a bit more, or stay about the same,
but the transmission will last far longer for sure because it's not shifting as often to make up for weak@$$ gears.

Compared to my other 3 this thing is slow unless you constantly hammer the throttle.

It'll put more strength through the tires to the ground with better axle gear.
If you want to be sure to gain acceleration potential, 3.73. If you're ok with it being slow, 3.42 will still help.

And in theory it should get better fuel mileage than the rest. It does not but that's OK. I live rural and maybe if I was on flat highway doing 80 all the time?

CAFE MpG test scores are typically idealistic exaggerations that can only be achieved by the kind of tame driving that would make me want to kill myself.
In the real world, going from 3.08 to 3.42 or 3.73 would result in either no MpG change, an incredibly negligible MpG change,
or an improvement in city MpG balanced out by a slight highway MpG penalty, which is mitigated by the 6L80 lasting even longer, even before getting tuned.

 

[Marky Dissod]

A tune will completely fix what GM screwed up. I normally don't even feel my 5-4 downshift! (very close to '17-'20 tune for 4-5 and 5-4, w/3.42)

Mileage will still suck ... I think mine went down a little. Partly because I unlocked the tcc in 2 & 3 ... But also because I'm less shy on the throttle.
(Since it will actually downshift now! AND feel smoother doing it.)

I used to rarely pass in heavy traffic, it just felt too laborious. Cars kept cutting in front, I'd have to slow.. Before long everyone was in front if me!
No more resistance to acceleration, you will use a little more gas in all likelihood.

Downshifting at 37-50% throttle feels much better than downshifting @ 80+% throttle. Sooner, smoother, and without the drama!.
Other tweaks make it shift quicker & smoother. ( torque adders and inertia factor are worth tweaking )

Everything applies to my daily driver tune. No excessive RpMs, no harsh shifts, no TCC bump.

Didn't you go from 3.08 to 3.42?
If so, do you ever wonder about 3.73?

 

[mikez71]

I did go from 3.08 to 3.42.
Nope! Personally *I* don't need 3.73..

The torque gain almost non-existent going from 3.08 to 3.42..
(I only notice it in 5 & 6, and only when lugging at low rpms)

I expected to feel 1st gear pull off the line better, but didn't notice it one tiny bit!!!
First noticeable thing was a little more frequent shifting (around town, low gears)

Also, I wouldn't want higher revs when cruising at 80-90mph.
And since upper gears downshift without much drama, (You don't get that torque curve with the gearing loading it down)
The '12 tune waits until higher throttle/rpms, then smooths out the shift, later tunes seem a little more direct, shifting as you apply throttle.
(I suspect '17-'20 also have a good 5-4 shift, because that's what I based my 5-4 schedule on)

HOWEVER, a heavier load and some hills might change my opinion.
I'm mostly flat ground, and maybe loaded with a couple passengers..

Biggest problem is the factory tune letting you get into 5&6 so early that you're at 1200rpms (or less?) cruising around..
Staying in a lower gear for more revs, same thing IMO. Cheaper and faster fix for most..

I just remembered another gear change I did.
A manual BMW 1.8L (maybe 140hp?). I swapped from a 3.45 to 3.23 iirc..
I was afraid it was going to bog off the line.. but it just gave me longer legs, a little more time before having to shift to 2nd.
I was swapping in a 3.2L anyways, but I was pleasantly surprised, it did not suffer even with a 1.8L!

I love your gearing charts Marky! And I generally agree with your assesments,
BUT I'm thinking there is a sweet spot (depends on your driving circuit), and a little extra gear doesn't always net noticeable gains.
For 3 speeds that don't have the gearing spread, and not low enough of a first gear, it probably makes a bigger difference.

 

[Marky Dissod]

I love your gearing charts Marky! And I generally agree with your assessments,
BUT I'm thinking there is a sweet spot, and a little extra gear doesn't always help.

No such thing as an engine that gets stronger / more powerful as it ages - and even if there were,
every other friction on/in the vehicle gains more friction as it ages, not less.
Also, does ANY vehicle get significantly lighter or more aerodynamic as it ages?
Don't forget that the vast majority of newer personal vehicles are not getting any slower.

The engine's sweet spot is not 1691RpM or 1837RpM or whatever, it's an RpM range. GM is coerced by CAFE to bias toward the lowest RpM of that window.
Then you buy it, then it gets heavier, older, maybe you (not you specifically) don't maintain the entire vehicle very well, maybe you sell it ...

Every GM truck with a 6L80E & OE 3.08, would've been better served by 3.42. Every GM truck with a 6L80E & OE 3.42, would've been better served by 3.73.
Featherfoots would not lose much if any MpG, and their transmissions would shift less often, thereby going further between rebuilds.
Leadfoots would get more smiles to the gallon (and @Doubeleive's molybdenum foot too!).

Also, as a mid-90s LT1 B-car enthusiast, I know the difference between 2.56 & 3.08 is effectively about 60 horse in terms of top speed,
the difference between 2.93 & 3.42 is 2000lb worth of towing capacity ... and 2.56 HURTS MpG AND 4L60E longevity unless ALL the miles are highway.

To oversimplify the above, I've an easier time explaining how a lil more better gear helps,
than anyone will explaining how a lil more better gear hurts, if only because GM nearly always chose the lowest / weakest axle gear they could get away with.

By the way, I don't like my gearing charts, but I think they work well enough for visual illustration purposes.

 

[mikez71]

I like your charts! See the gearing spread..

No argument here. No doubt the shorter gear gives more mechanical advantage..

I'm just saying I can't tell any difference when flooring it at a stop light, or flooring it at speed. Only time I can tell any difference is when I lug it in a high gear.!?

I think with a heavier load, I should notice more.

 

[Marky Dissod]

Guess I'm just old enough to prefer to cite benefits that are NOT immediately measurable with a stopwatch, even if more axle gear usually impress stopwatches.
I'm more about improving the transmission's strength (tow rating) / durability / longevity with minimal real-wordMpG losses,
and you of all people can testify that 3.42 costs very little in terms of MpG vs 3.08 with a 6L80E.

Also, mind that GM ALSO tends to upshift very or too early, and makes the driver press very far down before considering a downshift.
Were I you, I'd 'cross-pollinate' the PARTS of the shift schedules you like, til you get something that LOOKS LIKE yet EXCEEDS any GM OE shift map option.
This should include making the shift map more cooperative / responsive to driver requests for downshifts, how much so is of course up to you.

 

[West 1]

My 08 Denali has the 6.2L 6L80 and 3.42 gears. I would very much prefer the gears were 3.73 so it could use all 6 gears better. With 3.42 gears it only holds 6th on the highway if I am going 75 MPH. Any slower and it will hunt and peck between 5 and 6th. On totally flat ground it will stay in 6th but in Northern California you are never totally flat. 3.73's for me! ( I could have made this swap last year as I had to rebuild both differentials due to a bad bearing but at that time I only planned to rebuild the rear diff, never thought I would have to do both)

EDIT: saw the MPG question, I bet the 3.08, 3.42 and 3.73 would be within .5 MPG of each other and in many types of driving the 3.42 and 3.73 would be better than the 3.08 for MPG.

 

[mikez71]

Have you had it tuned? You are willing to put up with more RPM's from shorter gears, so why not tune it to hold at higher rpms with the gearing you have? And I'm not implying 4k rpms in a 3.08 will have the same torque output as 4k rpms on a 3.42, but I am saying I can't tell the difference in my lightly loaded truck on flat ground. ..NVM I see you want to use all 6 gears, so guessing you don't need to go much faster than 85mph or so (neither do I really..)

This should include making the shift map more cooperative / responsive to driver requests for downshifts, how much so is of course up to you.

Exactly. I will go so far as to say, a tuned 3.08 is nicer to drive than GM's 3.42 tune.

Not talking about longevity benefits..
And my comments are limited to my lightly loaded tahoe on flat ground.

I recommend people tune first, it might save you a gear swap. If not, you'll want to tune the new gears as well.

The lazy GM tune is too much to overcome with just gears unless you go extreme, in which case you will be turning extreme rpms on the highway.
(which maybe necessary when towing anyway, but not desirable for commuting)

BUT, I don't tow, so I could be way off base regarding towing..
(For that matter I haven't hit mountains at altitude, but the stock tune sucks on flat ground at sea-level!)

 

[Marky Dissod]

My 08 Denali has the 6.2L, 6L80, & 3.42. I'd very much prefer 3.73, so it could use all 6 gears better.
With 3.42, it only holds 6th on the highway if I am going 75MpH, any slower and it will hunt and peck between 5th & 6th.

Addressing this kind of thing by tuning improves transmission longevity. Every unnecessary shift avoided helps it last longer.
Instead of hunt-shifting between 5th & 6th, stay in 5th til it can use 6th without back'n'forth-ing between gears.

On totally flat ground it will stay in 6th, but in Northern California you are never totally flat. 3.73 for me!

Oddly enough I cannot answer definitively, but I'd bet that CAFE MpG test regimes are mostly flat with very few hills that are neither long nor steep.

EDIT: saw the MpG question. I bet 3.08, 3.42 and 3.73 would be within .5 MpG of each other,
and in many types of driving, 3.42 and 3.73 would be better than 3.08 for MpG.

My experiences with mid-90s fullsize LT1 sedans & wagons bears out similarly.
2.56 sedans & wagons only gained an MpG advantage on the highway, IFF they could stay in 4th-Locked long enough to wring out the extra MpGs.
In the vast majority of highway usages, 2.93, 3.08, & 3.42 yielded very similar highway MpG results, therefore 3.42 won.

In the city, no contest. 2.56 was miserable to drive compared to 2.93, 3.08, & 3.42, because 2.56 made 4th gear useless in any city situation,
and even 3rd was useless under 30MpH, so all you had left was 2 weak gears to accelerate around in.
Whereas with 3.42, you could be in 4th under 24MpH, plus you had 3 stronger gears to accelerate around in.

Back then the debate was '3.42 or 3.73', regardless of the car's original axle gear.
The hinge questions were 'can you afford a driveshaft upgrade?' & 'are you willing to lose up to 3MpG highway?' If 'Yes' to both, 3.73. If 'No' to both, 3.42.
3.42 became more popular as we all got older, gas prices went up, and driveshaft upgrades became more costly (but 3.73 was more fun under 60MpH).

 

[Marky Dissod]

... a tuned 3.08 is nicer to drive than GM's OE 3.42 tune.

Agreed with no caveats, except from a dead stop of course.
A 3.08 Tahoe with a well-tuned shift map, will usually have lil to no trouble keeping up with a 3.42 Tahoe hobbled by GM's OE shift map.

I recommend people tune first, it might save you a gear swap. If not, you'll want to tune the new gears as well.

So do I, largely because most axle gear upgrades can be very costly compared to tunes.
However, a used complete axle assembly with better gears is cost-competitive with a tune ... once you LOCATE that axle assembly; can't be getting any easier.
In my experiences, a gear upgrade is SLIGHTLY better for a transmission's longevity than a tune.

The lazy tune is too much to overcome with just gears unless you go extreme, in which case you will turn extreme RpMs on the highway
(which maybe necessary when towing anyways, but not necessary when commuting)

This is the major reason why I seldom suggest 4.10 for 6L80E trucks/suvs - except for 4WD Suburbans/XLs/ESVs.
For most short-wheelbase suvs 3.42 or 3.73 is sufficient, especially with 2WD.

 

[Doubeleive]

3.73 is alright but you loose a little top end