Jump to content
  • Sign up for FREE! Become a GM-Trucks.com Member Today!

    In 20 seconds you can become part of the worlds largest and oldest community discussing General Motors, Chevrolet and GMC branded pickups, crossovers, and SUVs. From buying research to owner support, join 1.5 MILLION GM Truck Enthusiasts every month who use GM-Trucks.com as a daily part of their ownership experience. 

6.2/6L80/3.73 vs 6.2/8L90 vs ???


Recommended Posts

Long lurker, but first post. I’ve done quite a bit of educational reading here on many threads and wanted to inquire on something. 
 

I’m in the market for a 14-18 Silverado or Sierra 1500. Ironically, I have an opportunity to score a very nice, almost ridiculously nice, condition 2014 6.2 SLT with the max trailering package (3.73) and acceptably low mileage. It has almost all, minus a few not so important, options I’d like. 2014 is really the only way to get one of these trucks w/o getting the 8 speed, unless I’m mistaken, so between that, age/mileage, and certainly factoring in the max trailing pkg, such a combo is difficult to find. Plenty of options exist to get the big motor in 15-18 trucks with the 8 speed, with max t pkg if necessary. 
 

Now, I don’t know that I’d go so far as saying that I prefer the “smoothness” of the 6 speed relative to the 8 speed but in our Yukon XL SLT (5.3/6 speed), honestly it offers a rather pleasant city and highway driving experience lugging around the kids. Mind you, we aren’t racing it with the kiddos onboard. It’s not quick, by any means, but it does the job.  I’d want more in a truck, thus the 6.2 thinking. Now, I’ve driven 5.3 + 8 speed combos and other non GM > 6 speeds, and they always feel jerky to me when doing simple cruising around town. I don’t feel it matters much on the highway, honestly. At elevated speeds, the feel difference is minimal IMO. I have NOT driven a 6.2/8 speed….yet. 
 

The general consensus in my reading here is that the 3.73 ratio in the 6 speed really makes the 6.2 come alive - several threads about towing (which I don’t do a lot of), quickness/fun-ness (important to me), etc. In addition, one might even say some feel the 8 speed should be avoided, others say just jump to the 10 speed. Opinions vary.
 

My question is, given the 8L90 issues, short lifespan relatively, etc does it make any sense to specifically consider an “older” 6.2/6L80/3.73 vs a 2015-2018 6.2/8L90 combo?  Or have a lost my mind completely due to information overload?  My primary concern is long term durability/reliability. Obviously, I don’t want a train wreck, and first year roll outs in a series always make me a little nervous even though the truck in question literally has been near flawless across its life. 
 

Curious what you connoisseurs and those having more experience in all these combos might do here - consider the 6.2/6L80/3.73 purchase, re-focus on a 6.2/8L90 - with or w/o NHT (I think is the code), or sit tight until a 6.2/10’s come into my budget a year or so from now? 
 

 

Link to comment
Share on other sites

Diff ratios used on 8 speed are different that 6 speed.

 

I think you find that the overall ratio (trans and diff) with the 8 speed gives a lower low and a higher high than the 6 speed. 

 

Same deal with the max tow (NHT versions) which has higher (numerically) ratio diff's.

 

 

  • Like 1
Link to comment
Share on other sites

My 14 (non max tow package) had the 3.42 6 speed, very quick truck off the line, and held RPM's a little higher, not as much 'lugging" at lower speeds.

 

The 16 I had, and now my 18 have/had the 3.23 8 speeds. Both have been very good, but takes a little more "motivation" to get them going at the same pace as my 14. Better MPG's with the 8 speeds, and tow just fine.

 

If you are looking at K2's, would really consider an 18, seems like it was the year they finally got most of the bugs worked out IMO.

Link to comment
Share on other sites

I posted a gear ratio spread sheet a while back comparing the 6 speed with 3.73's to the 8 and 10 speed  with the 3.23's and the 8 and 10 speed had "lower lowers and higher highs" as posted above.  The key though isn't how "low" the overall gear is, its how long the truck stays in that gear range and the 8spd and 10spd manage to operate in the lower gear ratio parameters for a longer duration than the 6 speed which in turn allows the vehicle to pull harder for longer even though the rear gear ratio is taller.  I'll see if I can find my spread sheet and post it again.

Link to comment
Share on other sites

6 Spd Auto Gearing (X:1)   4 Hi Final Ratios 4 Lo Final Ratios
1 4.03   15.03 40.44
2 2.36   8.80 23.68
3 1.53   5.71 15.35
4 1.15   4.29 11.54
5 0.85   3.17 8.53
6 0.67   2.50 6.72
         
         
Reverse 3.06   11.41 30.70
         
Axle Ratio 3.73   Crawl Gear Ratio (X:1)  
      40.44  
Transfer Case        
4 Hi 1      
4 Lo 2.69    

 

 

 

 

 

8 Spd Auto Gearing (X:1)   4 Hi Final Ratios 4 Lo Final Ratios
1 4.56   14.73 39.62
2 2.97   9.59 25.81
3 2.08   6.72 18.07
4 1.69   5.46 14.68
5 1.27   4.10 11.03
6 1   3.23 8.69
7 0.85   2.75 7.39
8 0.65   2.10 5.65
Reverse 4.86   15.70 42.23
         
Axle Ratio 3.23   Crawl Gear Ratio (X:1)
      39.62  
Transfer Case        
4 Hi 1      
4 Lo 2.69      

 

 

 

 

10 Spd Auto Gearing (X:1)   4 Hi Final Ratios 4 Lo Final Ratios
1 4.7   15.18 40.84
2 2.99   9.66 25.98
3 2.15   6.94 18.68
4 1.8   5.81 15.64
5 1.52   4.91 13.21
6 1.28   4.13 11.12
7 1   3.23 8.69
8 0.85   2.75 7.39
9 0.69   2.23 6.00
10 0.64   2.07 5.56
Reverse 4.87   15.73 42.31
         
Axle Ratio 3.23   Crawl Gear Ratio (X:1)
      40.84  
Transfer Case        
4 Hi 1      
4 Lo 2.69      
Link to comment
Share on other sites

Those are based on my own calculations from materials I have reviewed.  The reverse gear ratios would need to be validated.

 

Basically, the 8 speed and 10 speed transmissions do everything better, from top to bottom, even when the 6 spd is paired with the 3.73's.  If you pair the 6L80 with 3.42's or 3.23's then the 6l80 is not even remotely close.  The only real question would come down to reliability in which case the early 8 speeds did have issues but those same issues seem to be resolved in the newer models.  I have not had a single hiccup from my 2020 8-spd and I have 45k miles on it.

  • Thanks 1
Link to comment
Share on other sites

if you can score a clean truck pre-2017 get that sona-******, , the computer are easier to access and tune.

i know the tuners like the 8 speed because it can handle over 1000hp, but cost is not friendly for the home tuner. tcm unlocks $$$ the 8 speed can shift faster, but has way more rotational mass which robs you of power transfer.

 

6l80/90 is the way to go if you want tuning on a budget, the 2500 trucks is the best 6 speed, its built stronger as a 6L90.

Edited by pokismoki
Link to comment
Share on other sites

On 10/15/2021 at 7:51 PM, tdc5152 said:

Long lurker, but first post. I’ve done quite a bit of educational reading here on many threads and wanted to inquire on something. 
 

The general consensus in my reading here is that the 3.73 ratio in the 6 speed really makes the 6.2 come alive - several threads about towing (which I don’t do a lot of), quickness/fun-ness (important to me), etc. In addition, one might even say some feel the 8 speed should be avoided, others say just jump to the 10 speed. Opinions vary.
 

My question is, given the 8L90 issues, short lifespan relatively, etc does it make any sense to specifically consider an “older” 6.2/6L80/3.73 vs a 2015-2018 6.2/8L90 combo?  Or have a lost my mind completely due to information overload?  My primary concern is long term durability/reliability. Obviously, I don’t want a train wreck, and first year roll outs in a series always make me a little nervous even though the truck in question literally has been near flawless across its life. 
 

Curious what you connoisseurs and those having more experience in all these combos might do here - consider the 6.2/6L80/3.73 purchase, re-focus on a 6.2/8L90 - with or w/o NHT (I think is the code), or sit tight until a 6.2/10’s come into my budget a year or so from now? 
 

 

 

 

6L80 has a higher issue rate than the 8L90, at least where I work.  All day long.  I've lost track on how many 6L torque converters we've done, on how many got fluid pumps and some internals, on 4-5-6 clutch failures, entire transmission replacements because so much converter clutch material an metal went through them.

 

8L90 I would go 2018+newer.  If it hasn't had the fluid swapped out for shudder that would be the first thing to do.  Some of the funky shifts can be settled out by making that specific gear change like 15-20 times at the throttle % it does it.  Helps to learn that clutch/gear change.  So say you have a funky 2-3 shift, pop it into manual mode and make a bunch of 2-3 shifts.

 

As far as how they run/drive.  I'm on my 4th 6L.  I love them for the most part, but 8L and 10L drive sooo much better, especially the 8L in the T1 new trucks.  They tightened up the shift calibrations and tuning much better.  

 

3.73/6speed vs 3.42/8speed.  The 3.42/8speed would have even more gear multiplication throughout 1-4th or 5th gears.  8 speed lets the engine sit in the HP and or TQ bands better.  Watch some of the Ike Gauntlet videos on TFL truck.  Yes, the test is a more extreme test and and high elevation, but you can see where some of the GM 6 speeds fall short of the 8 and 10 speed trucks.  6 speed can get stuck in a lugging zone and start to fall off RPMs and out of the meat of the power range.  Even with 4.10s.  

 

6.2 8 speed NHT 3.42

2017 Chevy Silverado 1500 6.2L V8 vs Ike Gauntlet Review: World's Toughest Towing Test - YouTube

 

6.0 HD 6 speed 4.10

2015 Chevy Silverado 2500 takes on the Grueling Ike Gauntlet HD Towing Test - YouTube

 

6.6 new gas HD 6 speed 3.73

The New 2020 Chevy Silverado HD Gasser Broke Our Ike Gauntlet Scoring System - Here Is How! - YouTube

 

I know there is weight differences in the videos above, but you can still see how the two HD trucks get put in strange positions during the pull.  The switch DOWN to 3.73s in the 2020+HD was a mistake as well.  That truck needs the 10 speed all day long with those 3.73s.  

Edited by newdude
  • Like 1
Link to comment
Share on other sites

  • 2 weeks later...

Sorry all.  I've been away on business for a bit.  

 

Thank you for all your input.  This clarifies a lot of question marks I had.  Now it's time to take a few different configurations for a spin and complete the "feel" evaluation.  

 

Besides, the used car value/market is completely out of control (high) at the moment, so exercising a little patience is probably a good idea honestly.

 

Thanks again.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.