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Posted
3 hours ago, f8l vnm said:

don't even get me started on gear ratios and Gm . 

Why not offer other ratios as buy up options ? I don't get that part but making you pretty go directly to 3.23 unless you get the Max Tow . 

Ford lets you have 3.13, 3.31, 3.55 and 3.73 .  Even Ram allows a 3.91 along with 2 other ratios . 

Let's don't forget (though we're talking specifially about the 6.6 gas engine) that the Duramax also got neutered with only a 3.42 rear end choice, after years of having a 3.73 gear. Sure, it's all working for 99% of applications, but a choice would be nice.

Posted

chevy prolly will offer the 10spd in a bigger gas motor......does anyone offer just transmisson upgrades without a motor change  in HD truck?....i havent heard of one aside from 5.3 in 1500s ( 6, 8 and 10spds)

 

chevy will have the 10 spd in a bigger V8 gasser as upgrade i am guessing as upcharge

 

i have the 6 spd...while mpg could be better imo its not bad at all.....

Posted

It seems like the logical thing to to, after all they did change the rear gear for something, obviously not for milage, because it's the same.

 

Oh wait...... GM, no logic involved.

  • Like 1
Posted

Having worked in the industry for a period of time, some of these decisions are, unfortunately, driven by Federal regulations regarding emissions and fuel economy. I was told for every 5 Evo‘S produced, GM can build one Silverado (or Vice versa I cant recall specifically). I’m thinking maybe limiting the gasser to 3.73 may have something to do with some Federal standard GM has to meet. I do realize fuel mileage isn’t required on the window sticker for HD’s which meet different criteria; just a thought. It always seemed strange to me that the Duramax was limited to only the 3.73 (now the 3.42). Or maybe just GM being conservative and fearing a change to a lower (numerically higher) rear axle would create an expectation of higher tow rating.

Posted
On 10/23/2020 at 6:16 AM, TrailBoss1 said:

Having worked in the industry for a period of time, some of these decisions are, unfortunately, driven by Federal regulations regarding emissions and fuel economy. I was told for every 5 Evo‘S produced, GM can build one Silverado (or Vice versa I cant recall specifically). I’m thinking maybe limiting the gasser to 3.73 may have something to do with some Federal standard GM has to meet. I do realize fuel mileage isn’t required on the window sticker for HD’s which meet different criteria; just a thought. It always seemed strange to me that the Duramax was limited to only the 3.73 (now the 3.42). Or maybe just GM being conservative and fearing a change to a lower (numerically higher) rear axle would create an expectation of higher tow rating.

If that was the case then why does Ford give you so many options.

  • Like 2
Posted (edited)

I believe GM uses the 6 speed because it has a long track record of being reliable for fleet customers.  

 

Fleet customers buy gas engines and even thought the 6.6 is new the LS design is just as reliable.  

 

GM used the 6.0 gas engine in the 2500 from 1999-2019.  It is doubtful you will see a 10 speed until a body style update happens again.  2025 maybe???

 

 

 

 

Edited by OmahaBen
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Posted

I think Ford just simply treats their HD gas customers more equal to diesel. The whole reason they took the time to create the 7.3 gasser. Ford also uses it in far more platforms than GM is using the new 6.6, from the F-250 pickup to 14,500lb E-450, to the 24,000lb F-59 chassis. And of course the F-650 as well. Since the 8.1L’s discontinuation, GM barely dips their toe into big gas powertrains until recently. Meanwhile, Ford maintained the 6.8L V10.

 

I’d like to see GM get really serious about gas. GM still won’t offer a gas motor PTO combination. But Ford has and does. I think they believe in gas powertrains more than GM does.

  • 3 weeks later...
Posted

Ford is killing GM in the HD gasser lineup.  Not only with a bigger stronger motor, but have the 10 speed tranny, and in the 250 a choice between 3.55 and 4.30 rear ends.  In the 350 it is 3.73, and 4.30. 
I’ve been driving my 6.0 for 18 years and it has been great, but decided to wait on the 2020’s to get a bigger engine, but was disappointed with the 6spd, so I’ve decided to wait a little longer and see what they do for 2022.  If they still have the 6spd and no axle ratio options, I will go with the either the Ram or the Ford.  I’m planning on going to about a 12k lb 5th wheel in a couple of years, and while the Chevy would pull it, the For and Ram will do it better. 

  • Like 1
Posted

The L8T/6L90 combination is a fine base gasoline powertrain for the Silverado/Sierra HD's.  I do think GM really needs to offer a gas engine option in the Silverado medium duty 4500/5500/6500 and 6500XD LCF as well, and the L8T might not be big enough for those applications.  Before Covid there were a lot of rumors that a much larger 8L+ V-8 was in the works for the medium duty commercial trucks, and there was some speculation that such an engine might find its way into the Silverado/Sierra HD's.  However, I have not heard anything about a larger V-8 since earlier this year, so maybe the project was dropped or it was just a rumor to begin with. 

Posted

Having driven the L8T with 6 speed for a few weeks, I’m entirely satisfied. I had the 8 speed in my 2019 Trail Boss 5.3 and have found the 6 speed to be equally smooth (I know the 8 speed has had some issues but mine was fine). In addition to being a proven design, for my use, the ratios in the 6 speed are pretty well matched to the torque band of the motor. I agree a choice of axle ratios would be nice; but, because I don’t tow heavy, I’d likely stay with the 3.73 as a good compromise between capability and economy. The GM/Allison 10 speed is getting high marks; but with a torque rating of 1000 lb-ft, it would be overkill mated to the L8T and add significant cost. The ten speed from the 6.2 could handle the torque but may not meet HD durability requirements without upgraded components.

  • Like 1
Posted

Eventually we will see more gears as an option at least behind the 6.6 gas but if won’t be an Allison. The internals of that trans are so much heavier that it would be counter productive as far as fuel economy and wheel hp are concerned. Even if it was an 8 speed it would be better than what’s in it now IMO. I’d be happy with Ford’s 10 speed in it. 

 

We have two F-550’s at work with the 7.3 gas and 10 speed. These trucks are touching 10k plus with service bodies and the 10 speed makes them feel like they have more power than the v-10 6 speed they replaced even though it isn’t much higher in the hp and tq dept. No issues with the trans but the engine is junk. It’s super picky with fuel quality where the v-10 would drink anything, constantly eats plug wires, we’ve blown out several spark plugs, and had multiple injectors changed already in 20000 combined miles. I wouldn’t recommend the ford till they get it sorted. 

Posted

I have heard the 7.3L needs higher octane fuel.  With that large bore it probably needs dual ignition like the 6.2L Ford.  Are the spark plugs coming out of the heads like the old Ford Modulars?  I wonder how the head gaskets will hold up on the 7.3L long term.

Posted
On 10/22/2020 at 7:53 PM, ShotgunZ71 said:

Let's don't forget (though we're talking specifially about the 6.6 gas engine) that the Duramax also got neutered with only a 3.42 rear end choice, after years of having a 3.73 gear. Sure, it's all working for 99% of applications, but a choice would be nice.

 

Sure it went to 3.42 but it gained 4 gears.  1st gear in the 10L1000 is 4.54:1 vs. 3.10:1 in the Allison 1000.  The 10L/3.42 gear multiplication in 1st through 8th gears is higher than the Allison/3.73 combo is 1st through 5th.  Could they put 3.73 in it?  Sure.  Would it be necessary?  No.  See 36,000lbs max tow rating.

 

The 6.6 gas is the one that got neutered here.  GM even got rid of the 3.73 on 2015-2019 trucks for a reason with the 6.0/6A.  It was the better pairing.  2007-2014 trucks with 3.73 gears on average saw a 3500-4000lbs tow rating loss over the 4.10 trucks.  GM went backwards on the 6.6 with 3.73 and 6A.  Needs either to go back to 4.10 or they just man up and do the 10L90 and leave the 3.73.  I still think that the joint venture had something to do with it that's why Ford got to do the gas with 10 speed HD trucks first.      

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