Looking to Buy '18-'19 Tahoe Engine/Trans questions

[Timbers68]

So we're finally close to purchasing a Tahoe except for a couple things.

Choosing between a 5.3 6 speed with the max trailering pkg 3.42 rear gears, or the 6.2 10 speed w/3.23's. Whatever I end up with will be 4WD and hopefully in the 15-30k mileage range.

I have a small amount of knowledge on the 6L80/90 transmissions in stock form, but none on the 10 speeds. I have very limited knowledge about tunes/tuners but have good amount of automotive knowledge and background. I recently test drove a 2020 Tahoe 5.3 w/3.42's and couldn't even feel it shift. Last year my wife and I rented a 2020 Expedition with the 10 speed and same thing: slosh box and it did a lot of whining at idle after several hundred miles (truck had 20k on it). Impressed with the power the Expedition had.

1) If I purchase a programmer (Hypertech, superchips, HP Tuner), is it possible to make either transmission shift firm and be reliable for 100k+?

2) Seems like both engines are reliable, but after test driving a 2020 Tahoe 5.3 w/3.42s, I wasn't impressed with the amount of power it didn't seem to have. I do admit I wasn't putting it to the wood, but drove it like I would my '05 L33 Silverado. Choosing the 6.2 seems like a no brainer except the unknown (to me) reliability of the 10 speed trans. Anyone on here with a lot of miles on a 10 speed? Opinions?

3) Seems like either choice, they get about the same fuel mileage. Those here who have a tune/tuner, does that fuel mileage tend to go up, or down? How much.

At some point I may put an A/T tire on it, no lift, maybe a level lift if they need it.

Thanks in advance.

 

[Timbers68]

Anybody?

Happy Friday.

 

[JohnC12]

I really can’t answer your questions since I don’t tune and don’t have a lot of miles on my Tahoe. However, I can make a couple of comments on the 5.3 vs the 6.2.

I owned a 2018 Cadillac Escalade with 6.2 and 10 speed and I thought they paired very nicely. Shifts we’re smooth as butter. However, I decided to get rid of the Escalade because of the rough idle problem I had which I understand is quite common with this motor.

When I was in the market for a new SUV, I knew I wanted to go with the Tahoe with the 5.3. Obviously for the reason mentioned above, but I also didn’t want to have to put high octane fuel in my truck. Based on the fact that you’re looking to tune, this may not be a concern for you, but it was for me.

Overall, I’m very happy with me decision - my 2019 with the 5.3 and 6 speed (4WD with tow) is awesome… zero complaints.

 

[JohnC12]

BTW… welcome to the forums and good luck… look forward to hearing which direction you go.

 

[Timbers68]

I really can’t answer your questions since I don’t tune and don’t have a lot of miles on my Tahoe. However, I can make a couple of comments on the 5.3 vs the 6.2.

I owned a 2018 Cadillac Escalade with 6.2 and 10 speed and I thought they paired very nicely. Shifts we’re smooth as butter. However, I decided to get rid of the Escalade because of the rough idle problem I had which I understand is quite common with this motor.

When I was in the market for a new SUV, I knew I wanted to go with the Tahoe with the 5.3. Obviously for the reason mentioned above, but I also didn’t want to have to put high octane fuel in my truck. Based on the fact that you’re looking to tune, this may not be a concern for you, but it was for me.

Overall, I’m very happy with me decision - my 2019 with the 5.3 and 6 speed (4WD with tow) is awesome… zero complaints.

Thanks for this info.

When you say rough idle, like it was misfiring? Guess I need to do a search on this. I haven't seen that concern.

Did you seem to get similar gas mileage between the two?

 

[Miami-Dade]

I have a 2016 Tahoe LT with the 5.3 2 WD.

I have a 128K miles on my Tahoe. The 5.3 has enough power for me. I drive from Miami-NYC several times a year and can keep up with anything that is out there on the highway. I run 87 octane [mostly Exxon-Mobil] since new.

The 2018-2019 are good years to get. Some of the 2015-2017 had A.C Condenser issues and Brake Booster issues. I would shoot for a 2019 even if it had slightly higher miles.

I get slightly rough idle here and there but nothing to annoy me. I had several rental 2015-2016 Tahoe-Suburban before buying one and they all did the same thing.

As far as a tune goes was thinking of getting a Black Bear Performance tune. Everyone here who got one loves it.

 

[Doubeleive]

It really boils down to what you want
the 6.2l has more power, yet slightly lower towing capacity with the gear ratio
the 6.2l will get slightly lower mpg as well, but has a nice trade off with more power
the 6sp and 10sp should both be fine in that year range, you don't have to feel the gears bang for it to work good, but it can be tuned that way.
a tune will help a lot in either case
@BlackBearPerf

 

[JohnC12]

Thanks for this info.

When you say rough idle, like it was misfiring? Guess I need to do a search on this. I haven't seen that concern.

Did you seem to get similar gas mileage between the two?

Exactly... like it was misfiring when at idle... at speed, there were no issues. I was constantly cleaning my throttle body which would, for a short time, take care of the issue. But without fail, it would start idling rough again. I'd swear she ran better after an oil change, but that was probably just in my head. Other's have reported broken motor mount as the culprit. There's a laundry list of suspected reasons, and quite frankly, I didn't want to deal with the stealerships so I just sold it. Google 6.2L rough idle and you'll find tons of good stuff on the issue. Oh wait... just do a search on here... plenty of posts on here about the issue.

I saw slightly lower gas mileage with the 6.2, but like Doubeleive mentions, there's a bit more pep as compared to the 5.3. If you're worried about MPG, I'm guessing you'd prefer not to spend more on gas? If so, don't forget that you have to put 93 octane in the 6.2, or it will run rough.

 

[Doubeleive]

the "general" fix for rough idle is to keep the intake clean and put injector cleaner in it either as needed for a few tank fulls or on a regular basis as a routine, I add 2 bottle's per full tank of gas to my vehicles at least once every 3 months, sometimes more often just depends on when I remember to do it, I buy the stuff from walmart by the dozen it's only about $1.25. Other options would be a injector service.

 

[JohnC12]

the "general" fix for rough idle is to keep the intake clean and put injector cleaner in it either as needed for a few tank fulls or on a regular basis as a routine, I add 2 bottle's per full tank of gas to my vehicles at least once every 3 months, sometimes more often just depends on when I remember to do it, I buy the stuff from walmart by the dozen it's only about $1.25. Other options would be a injector service.

I had a fundamental problem buying a $90k (my MSRP was $89,525) Escalade only to have to clean the TB and MAF on a regular basis. And on top of that I have to put injector cleaner in a brand new vehicle? Now way! And lets not forget that it's a royal PITA to get to the TB. Unacceptable in my opinion.

 

[Doubeleive]

I had a fundamental problem buying a $90k (my MSRP was $89,525) Escalade only to have to clean the TB and MAF on a regular basis. And on top of that I have to put injector cleaner in a brand new vehicle? Now way! And lets not forget that it's a royal PITA to get to the TB. Unacceptable in my opinion.

true but I keep mine maintained and it runs fine, throttle body shouldn't be hard to get to at all, I can take the intake off in a couple minutes, changing the battery on the other hand is not as fun.

 

[Timbers68]

Thanks to everyone who has replied.

Keep em coming.

 

[lbenson]

10 speed has been a huge upgrade from the 8 speed in my 15 Denali... have an 18 Denali now both Denalis had/have the 6.2L. Used to have a 15 XL SLT with the 5.3L and 6 speed. Both my 6 speed and 8 speed transmissions sucked... the 6 speed would randomly clunk on shifts up or down and the 8 speed failed at 175k. Didn't keep the 15 XL 6 speed past 60k miles so who knows what happened to that transmission. The 10 speed in my current Denali is much smoother. 85k miles on it now and no concerns yet. However 2018 was the first year for the 10 speed so we will see longterm life in the coming years.

As far as MPG goes... both the 6.2L's I've had get better than the 5.3L I had in the XL (Could just be that my Denalis are the short wheelbase vs the 5.3L was long wheelbase.. less weight in the shorter ones). Decently flat highway in summer months I can get 24 mpg cruising 75-80mph in the Denali as where my 5.3L would be just over 20 mpg (but again more weight than the Denali).

Know two individuals who had 6 speeds (with 5.3L) fail in their Suburbans right before 80k miles. One was a 16' and one was a 17'. Some threads on here about dealing with thermostat issues that cause these failures. Unsure if there were any modifications in the later years to prevent failures.

An interesting side note is that GM dumped the 5 year 100k powertrain warranty after 2015 models for a 5 year 60k powertrain warranty in 2016... funny how the 6 speeds were failing before the 100k mark after that. Thought I heard some rumblings a while back that GM knew these transmissions failed and did that on purpose.. but who really knows.

Some additional edits: If you're gonna tow or have substantial weight in the back of the truck... I always use two-haul mode. Much better on the transmission.

As far as the 5.3L vs the 6.2L... after having the 5.3L then the 6.2L I would go with the 6.2L all the way. More power and takes less to get the truck moving. Fun to drive too if you like to get on it every once and while like I do .With a surfboat too.. the added power makes it easier to tow around town. While it will take premium fuel (vs regular in the 5.3L)... the few extra dollars every fill up are worth it to me.

This is just my two cents and by no means is it all right... just my experiences I figured I would share!

 

[Timbers68]

10 speed has been a huge upgrade from the 8 speed in my 15 Denali... have an 18 Denali now both Denalis had/have the 6.2L. Used to have a 15 XL SLT with the 5.3L and 6 speed. Both my 6 speed and 8 speed transmissions sucked... the 6 speed would randomly clunk on shifts up or down and the 8 speed failed at 175k. Didn't keep the 15 XL 6 speed past 60k miles so who knows what happened to that transmission. The 10 speed in my current Denali is much smoother. 85k miles on it now and no concerns yet. However 2018 was the first year for the 10 speed so we will see longterm life in the coming years.

As far as MPG goes... both the 6.2L's I've had get better than the 5.3L I had in the XL (Could just be that my Denalis are the short wheelbase vs the 5.3L was long wheelbase.. less weight in the shorter ones). Decently flat highway in summer months I can get 24 mpg cruising 75-80mph in the Denali as where my 5.3L would be just over 20 mpg (but again more weight than the Denali).

Know two individuals who had 6 speeds (with 5.3L) fail in their Suburbans right before 80k miles. One was a 16' and one was a 17'. Some threads on here about dealing with thermostat issues that cause these failures. Unsure if there were any modifications in the later years to prevent failures.

An interesting side note is that GM dumped the 5 year 100k powertrain warranty after 2015 models for a 5 year 60k powertrain warranty in 2016... funny how the 6 speeds were failing before the 100k mark after that. Thought I heard some rumblings a while back that GM knew these transmissions failed and did that on purpose.. but who really knows.

Some additional edits: If you're gonna tow or have substantial weight in the back of the truck... I always use two-haul mode. Much better on the transmission.

As far as the 5.3L vs the 6.2L... after having the 5.3L then the 6.2L I would go with the 6.2L all the way. More power and takes less to get the truck moving. Fun to drive too if you like to get on it every once and while like I do .With a surfboat too.. the added power makes it easier to tow around town. While it will take premium fuel (vs regular in the 5.3L)... the few extra dollars every fill up are worth it to me.

This is just my two cents and by no means is it all right... just my experiences I figured I would share!

Maybe you had 3.08 gears in the 5.3 truck you had? I've read they don't get as good of mileage as the ones with the 3.42 gears.

I've never liked the idea of the 6 speeds having the TECHM (ie the TCM) inside the transmission. Most all of the 6 speeds I've worked on were because of TECHM failure and most under or just over 100k. As I mentioned in my OP, I've not been into any 10 speeds.

85k is a fair amount of miles. Do you ever get a 'whine' sound coming out of the trans?

Thanks for your reply.

 

[lbenson]

Maybe you had 3.08 gears in the 5.3 truck you had? I've read they don't get as good of mileage as the ones with the 3.42 gears.

I've never liked the idea of the 6 speeds having the TECHM (ie the TCM) inside the transmission. Most all of the 6 speeds I've worked on were because of TECHM failure and most under or just over 100k. As I mentioned in my OP, I've not been into any 10 speeds.

85k is a fair amount of miles. Do you ever get a 'whine' sound coming out of the trans?

Thanks for your reply.

My 5.3L had the heavy duty trailer package so it did have the 3.42 gears. Had the trailer brake controller and everything.

Unsure if I get any whine sound coming out of the trans, nothing that I can really hear as of now. As far as I can remember from the 15 with the 8 speed (got rid of it a year ago now) and the 18 with the 10 speed they both sound similar when driving.

Friend of mine who is a service advisor with the dealer I always work with has told me in the past he has yet to see any trucks come in with issues on the 10 speeds. Could also be there are not enough high mileage examples to see any issues yet.

I intend (as of now) to keep this truck as long as possible (200k+ miles). I would imagine I will hit 100k before the end of this year.

 

[fozzi58]

The 6 speed trans is tunable. The 10 speed is not with the factory TCM - you need to add/swap or replace in module in order to tune the trans (Google House of Power T93 or T97 - I don't remember I'm going off recall.) The 10 speed is a very good trans but as stated by @lbenson there aren't enough high mileage examples.

The 6 speed can be made bullet proof with cheap dollar mods. Change the fluid and filter every 25k - forget what GM tells you. The next biggest thing it having the thermostatic valve pulled from the trans so it just flows the trans fluid without any restriction. It sits in the outflow of the trans lines. Pull the lines and remove the valve. If you want an upgrade, replace the lines - The trans lines were upgraded. Trans temps will drop from 185 to 140 for normal driving. With the trans lines/valve, fresh fluid, and the tune, trans should easily hit 100k even with towing.

This might be overkill for your situation but the next big leap is an aftermarket torque converter. Its bigger dollar but a lot of the trans issues stem from the crappy factory converter. Get a big brand name like Circle D, TCI, Yank, etc.

And I've got 3.08s out back in the Suburban.

Let me know if you need more questions answered.

 

[Plimbob]

FWIW -

I have a 2017 Tahoe 5.3L with 90k so I can't opine on the 6.2L. I have had issues with the AC Condenser, the brake booster and the 6 speed failed at 87k. When I had the 6 speed rebuilt, I have them put in a Billet TQ, Sonnax valves and upgraded thermostat. The trans shift better and considerably firmer, however, it does downshift pretty ******* de-acceleration into 3rd so I need to look at that further. BTW - the shop who rebuilt the trans said they do 6-8 of the 6 speeds a month. Obviously, a serious problem.

I have tuned it with the Diablo tuner and custom tune by Lew Eaton. It runs and tows better. I tow a 20 ft fishing boat around the Midwest and it tows pretty well.

I am getting some of the vibration issues at 65-75 mph as some others have complained about. I have checked the tires, tie-rod and ball joints not issues there. So still working on this issue.

 

[vcode]

So I think the throttle mapping is a lot different on the '15's and later compared to the previous gen. I drove a '16 and thought it was a real dog compared to my '10. But if you really put your foot in it the'16 was probably a little quicker. The newer trucks are really lazy until you stomp on it. Not sure if a tune can correct or improve that. Just avoid the 8 speed!

 

[Timbers68]

My 5.3L had the heavy duty trailer package so it did have the 3.42 gears. Had the trailer brake controller and everything.

Unsure if I get any whine sound coming out of the trans, nothing that I can really hear as of now. As far as I can remember from the 15 with the 8 speed (got rid of it a year ago now) and the 18 with the 10 speed they both sound similar when driving.

Friend of mine who is a service advisor with the dealer I always work with has told me in the past he has yet to see any trucks come in with issues on the 10 speeds. Could also be there are not enough high mileage examples to see any issues yet.

I intend (as of now) to keep this truck as long as possible (200k+ miles). I would imagine I will hit 100k before the end of this year.

Interesting that the mileage was that different knowing your 5.3 had the 3.42 package.

Great info about your friend/service advisor at the dealer about the 10 speeds.

Thanks

 

[K2 Kaiju]

I have a 87 diablo tune on my 18 with 6 speed and 5.3. I may do a Lew tune this summer, but just switchihg to the firm shift, cutting the afm, and increasing throttle response 20% makes it a completely different vehicle, though I also have a airaid jr and corsa exhaust. I like being able to pull the tune if I need to go to dealer, though I have not needed to yet. I had considered a whipple, but really dont feel underpowered any more, nor do I want to buy premium gas...