Which Gear for SC "Foothills"?

[Jerome Nelson]

Howdy!

I've just moved from very flat, Central Florida — to hilly, Greenville area, South Carolina.

I had the automatic transmission rebuilt (twice) and upgraded the transmission radiator/cooler.

I remember my Florida, transmission mechanic saying something about keeping the Tahoe in 3rd gear (instead of "D"), for our trip to mountainous, North East Tennessee. However, I'm not sure which is appropriate for our moderate, hilly region in Upstate Carolina. (To be clear, I'm not towing or hauling anything. Just a daily driver with kids.) Thoughts?

Also, when we do take a trip to the mountains (1 hour away), should we be in 3rd gear?

Vehicle Details:
2000 TWD 5.3 Tahoe
205K Miles
Automatic Transmission: 4L60E 4-X Speed

 

[Marky Dissod]

You'l never get 18MpG uphill. If the hills are steep or long enough, your axle gear is 3.73 or less,
and your 4L60E is 'indecisive' between 3rd & 4th (or worse - between 3rd & 2nd!),
it may be very helpful to put the shifter in '3' to avoid 4th when going uphill.

(If you somehow got lucky and your axle gear is 4.10, nevermind what your mech said about using 3rd to avoid 4th.)

That said, if you're NOT towing / hauling, it'd be better for the 4L60E in the long run to have the pcm tuned to be less 'shifty'.
If your axle gear is 3.42 or less, using Tow / Haul mode may not be helpful enough.

 

[Fless]

You'l never get 18MpG uphill. If the hills are steep or long enough, your axle gear is 3.73 or less,
and your 4L60E is 'indecisive' between 3rd & 4th (or worse - between 3rd & 2nd!),
it may be very helpful to put the shifter in '3' to avoid 4th when going uphill.

(If you somehow got lucky and your axle gear is 4.10, nevermind what your mech said about using 3rd to avoid 4th.)

That said, if you're NOT towing / hauling, it'd be better for the 4L60E in the long run to have the pcm tuned to be less 'shifty'.
If your axle gear is 3.42 or less, using Tow / Haul mode may not be helpful enough.

^^^ THIS. You want to avoid having the transmission constantly going in and out of 4th gear.

What are the "Gxx" RPO codes that are on the sticker in the glovebox? That would tell us what the diff ratio is.

 

[Doubeleive]

Howdy!

I've just moved from very flat, Central Florida — to hilly, Greenville area, South Carolina.

I had the automatic transmission rebuilt (twice) and upgraded the transmission radiator/cooler.

I remember my Florida, transmission mechanic saying something about keeping the Tahoe in 3rd gear (instead of "D"), for our trip to mountainous, North East Tennessee. However, I'm not sure which is appropriate for our moderate, hilly region in Upstate Carolina. (To be clear, I'm not towing or hauling anything. Just a daily driver with kids.) Thoughts?

Also, when we do take a trip to the mountains (1 hour away), should we be in 3rd gear?

Vehicle Details:
2000 TWD 5.3 Tahoe
205K Miles
Automatic Transmission: 4L60E 4-X Speed

not towing, no just drive it. if there was any other legitimate reason to put it in a lower gear it would say so in the owners manual

 

[Jerome Nelson]

Thank you all for replying!

Marky — Apologies. TBH, I didn't understand most of what you are saying. :/

Also, I'm not as concerned about gas mileage. I'm mostly concerned about burning out my transmission (again)!

Fless — Attached is the info from the glovebox. But, I can't make heads or tails out of it.

Doubelieve — I believe the thought from the transmission mechanic (Florida) is to keep it in "3rd", instead of "D", which I think he was saying was actually "Overdrive". I think he was saying that overdrive would wear out the transmission, by constantly shifting.

Bonus question: Is "3rd" the same thing as "D" with "Tow/Haul" engaged? (If so, I hate the way it lurches when it shifts - with or without a trailer.)

I appreciate any insight anyone can share!!

 

[Doubeleive]

Thank you all for replying!

Marky — Apologies. TBH, I didn't understand most of what you are saying. :/

Also, I'm not as concerned about gas mileage. I'm mostly concerned about burning out my transmission (again)!

Fless — Attached is the info from the glovebox. But, I can't make heads or tails out of it.

Doubelieve — I believe the thought from the transmission mechanic (Florida) is to keep it in "3rd", instead of "D", which I think he was saying was actually "Overdrive". I think he was saying that overdrive would wear out the transmission, by constantly shifting.

Bonus question: Is "3rd" the same thing as "D" with "Tow/Haul" engaged? (If so, I hate the way it lurches when it shifts - with or without a trailer.)

I appreciate any insight anyone can share!!

you have 3.73, there should be no reason to put it in 3rd.

 

[Fless]

you have 3.73, there should be no reason to put it in 3rd.

Agree with this and yes, unless you tow (which you said you aren't doing). But if you use D then watch for frequent shifts from 4-3 and 3-4; if it's happening a lot use 3 to prevent that.

Do you have a transmission temp gauge in the cluster? If so, be sure to monitor the temps, if just to put your mind at ease.

BTW, if you're going to tag someone be sure to start the tag with the "@" symbol, then start typing the member's name and pick it from the dropdown list that appears. Otherwise your target might not see it.

 

[Marky Dissod]

Marky — Apologies. TBH, I didn't understand most of what you are saying. :/
Also, I'm not as concerned about gas mileage. I'm mostly concerned about burning out my transmission (again)!

Fless — Attached is the info from the glovebox. But, I can't make heads or tails out of it.

Doubelieve — I believe the thought from the transmission mechanic (Florida) is to keep it in "3rd", instead of "D", which I think he was saying was actually "Overdrive". I think he was saying that overdrive would wear out the transmission, by constantly shifting.

Bonus question: Is "3rd" the same thing as "D" with "Tow/Haul" engaged? (If so, I hate the way it lurches when it shifts - with or without a trailer.)

Ok, good, you're more concerned with your 4L60E's longevity than with MpGs.
Your glovebox says your rear axle is 3.73 (GT4).
'D' allows all 4 gears. '3' disables 4th, allows 3rd, 2nd, and 1st, applies overrun clutches during decelerations in 3rd.
This is why I suggested having your pcm reprogrammed / 'tuned', to preserve your overrun clutches.

No, '3' is NOT the same as 'D' with Tow / Haul engaged.
Tow / Haul changes the shift personality of the 4L60E to protect the engine & transmission when towing / hauling.
Specifically, it protects from not putting enough power (or too much) to the ground, by choosing gears less often and far more carefully.

If you hate the way it lurches enough, that'd be another reason to have your pcm tuned.
Otherwise, you'll just learn to live with it or find simpler ways to avoid it, even if they are less effective than a tune.

If you've tired of what I've said, maybe someone else will explain it better?

 

[Jerome Nelson]

Thank you, again to @Marky Dissod , @Fless , & @Doubeleive ! You took a weight off me!

About "tuning" — I've looked into it several times, and I'm interested, but I'm finding the cost way outweigh the (understood) benefit. (non-Mac PC, +Software, +Credits, etc.).

FYI — the "lurching" only happens with "Tow/Haul" engaged. So, I can live with it, as I only tow/haul about every 6 months or so.

@Fless — I wish I had a transmission temp gauge! I just have to be satisfied with knowing I more than doubled the transmission cooler.

 

[Fless]

@Fless — I wish I had a transmission temp gauge! I just have to be satisfied with knowing I more than doubled the transmission cooler.

You can monitor the transmission temp with a simple OBD dongle and a smarphone, so it might be something to look into.