2015 Silverado & Sierra to get 8-speed transmission

[j-ten-ner]

...Rear axle means next to nothing. The overall drive ratio in each gear is all that matters...

 

Only partially true.

It just doesn't make sense to have a rear axle ratio of 1:3 when you need a 1st gear ratio of 25:1 just to get enough torque to the drive shaft to spin the wheels.

That would be a waste of efficiency just to gear "down" and then "up" again.

 

I'm convinced that the 8 speed and a 3.08 ratio will just work fine. You get 2 goals at once. Enough towing power (smaller gaps between the gears) and fuel economy.

 

so long

j-ten-ner

[kutu]

I think it would have been nice to get the 6-speed transmission right instead of it (or the transfer case) clunking all the time. Also, isn't this a shared design with Ford? My last Ford transmission had to be rebuild twice and then finally was replaced after a lengthy, time consuming fight... all before 38K. And every Ford my family has had prior has had transmission issues. Oddly, never a transmission issue with a Chrysler product - go figure! Haha...

I agree that clunking drove me crazy!!

[DanMan_S]

 

 

The 8L90 is a HD trans and wont be available in a #1500 truck. This transmission is not a joint venture with ford. A LD 8 speed is in the works.

 

Where are you getting your information? Even GM's own press release for the Silverado clearly mentions the 8L90E by name in the 1500's and gives a breakdown of the gear ratios:

 

 

[DanMan_S]

The 2015, 6.2L, 8 Speed Denali's are getting the 3.23 rear end. A colleague of mine just had his ordered accepted yesterday for the truck.

[LongrangeLauber]

Is this going to be an optional trans or is this standard with the 6.2?

 

Sent while in 'Murica...

[DanMan_S]

Is this going to be an optional trans or is this standard with the 6.2?

 

Sent while in 'Murica...

 

This is whats listed on the GM order book page, it looks like it's standard since it says "included with the 6.2L".

 

 

Edited August 23, 2014 by DanMan_S

[LongrangeLauber]

Wonder how much extra it would cost as the option then? I would have to drive a 6.2 with both a 6 and 8 speed to see if it would be worth probably the ~$1000 upgrade

 

Sent while in 'Murica...

[DanMan_S]

Wonder how much extra it would cost as the option then? I would have to drive a 6.2 with both a 6 and 8 speed to see if it would be worth probably the ~$1000 upgrade

 

Sent while in 'Murica...

 

That's a good question. I have the quote/pricing summary for the truck I plan to order, but at this time all of the pricing is blanked out.

 

[Cowpie]

Decided to pull out the spreadsheet I have that I can plug in tire revolutions per mile, transmission gear ratios, and differential gear ratios and it will give me road speed at various RPM's. Plugged in the ratios from the 8L90 trans and used 3.23 and 3.08 differential ratios. Based on the numbers, it looks like my 2013 will be the last GM pickup I ever own. I rarely ever use the 6th gear on my 2013 now in front of 3.42 diff, after running the numbers on the 8L90 and 3.08 and 3.23 diffs, I would hardly ever be using 7th and never use 8th. Hardly seems worth considering such a setup. Maybe 3.42, but then I would still be not using the top gear often, like I am barely using it now with my present 6 spd.

 

I like how they like to trumpet their power levels on their engines, but you have to reach screaming RPM's to get it. If they would supercharge or turbocharge the engines so that they could get max torque at lower RPM ranges where people actually run their engines, it would cause me to sit up and take notice better.

 

http://www.gmfleetorderguide.com/NASApp/domestic/graytabcontroller.jsp?graytabtype=1&rpoid=54277&vehicleid=14682&section=engineAxle

 

 

 

 

Edited August 24, 2014 by Cowpie

[Jsdirt]

Same idea with the Ecoboost. Engineers can't fight the laws of physics no matter how many fancy promotions the marketing team comes up with. Smaller engine is gonna need help (turboS .... TWO of them ...) to make big numbers. Can't wait to see what happens to those engines after 200k miles of hard work ...

 

I get annoyed by ONE downshift. Imagine the thing kicking down 4 gears at once just to keep a tiny engine in the powerband ....

 

The old addage still rings true this very day: THERE'S NO REPLACEMENT FOR DISLPACEMENT.

 

 

..... Based on the numbers, it looks like my 2013 will be the last GM pickup I ever own. ......

 

...

I made that decision with my '07 ....

Edited August 24, 2014 by Jsdirt

[Big Whiskey]

Decided to pull out the spreadsheet I have that I can plug in tire revolutions per mile, transmission gear ratios, and differential gear ratios and it will give me road speed at various RPM's. Plugged in the ratios from the 8L90 trans and used 3.23 and 3.08 differential ratios. Based on the numbers, it looks like my 2013 will be the last GM pickup I ever own. I rarely ever use the 6th gear on my 2013 now in front of 3.42 diff, after running the numbers on the 8L90 and 3.08 and 3.23 diffs, I would hardly ever be using 7th and never use 8th. Hardly seems worth considering such a setup. Maybe 3.42, but then I would still be not using the top gear often, like I am barely using it now with my present 6 spd.

 

I like how they like to trumpet their power levels on their engines, but you have to reach screaming RPM's to get it. If they would supercharge or turbocharge the engines so that they could get max torque at lower RPM ranges where people actually run their engines, it would cause me to sit up and take notice better.

 

http://www.gmfleetorderguide.com/NASApp/domestic/graytabcontroller.jsp?graytabtype=1&rpoid=54277&vehicleid=14682&section=engineAxle

 

 

 

 

I agree. 6th gear with 3:42's is almost useless, even with 32" tires. Maybe the 2500HD's will get 4:10's with the 8-speed. A 6.2, 8-speed, and 4:10's would be a blast to drive. As much as I hate to say it, I've considered getting a Ford Super Duty for my next rig, because you can get a 4:30 rear end with the gas engine.

[Cowpie]

Yeah, even Ford is still offering the 4.11 in their F150, at least in the build option on their website. Being the vast majority of my running around is on roads that I rarely see any speed over 65, I have really been thinking hard about 4.11 diff change in my 2013 even using stock tires. In 6th, at 65 mph, I would still be comfortably at around 2000 RPM. And my 2013 5.3L seems to do real well in that RPM range on the rolling, hilly terrain I am usually on. For now, going no higher than 5th with the 3.42's puts me in the same RPM range, just roughly 100 RPM higher than it would be in 6th with 4.11 at the same speeds.

[MikeNH]

Donno what you two are doing different but I'm always able to run at speed in 6th. Even when I moved and had the trailer on the back the trans could keep the truck moving in 6th.

[LongrangeLauber]

With my 60e and 35's with 4.88's my truck runs about 2k RPM's at 60mph. It can tow at that rpm but them 60e's have a very weak 4th gear. I believe the 6 speed and 3.42 gears are fine. 3.73 wouldn't be bad either. I feel like if I got a new 8 speed I would be swapping to a steeper gear.

 

The nice thing about the higher gear is that it is a stronger ring and pinion cause there's more surface contact and more material there. So the rear end should be fine haha

 

Sent while in 'Murica...

[Cowpie]

Donno what you two are doing different but I'm always able to run at speed in 6th. Even when I moved and had the trailer on the back the trans could keep the truck moving in 6th.

 

It isn't that I can't run in 6th, but the rolling hills, two lane roads I mostly drive on in my area, the trans is down shifting on every little hill, because the RPM's are too low in the power band in 6th and the pickup drops too much speed on those hills. And speeds are rarely over 65 mph. And forget the cruise except on the interstate. Between the down shifting and the ECM only knowing one method to get back to the cruise setting... floor it. This all is hard on the trans, increases heat in there, bad on fuel economy, and just plain a sour driving experience. So, I leave in manual mode, and no higher than 5th. All that downshifting stuff virtually eliminated and trans runs cooler. Pickup maintains speed better on hills, even with trailer or heavy load, and fuel economy remains fairly consistent. The engine just seem to do its best work from a power and economy standpoint, on the roads I primarily drive on, loaded or unloaded, at around 1800-2200 RPM. And with speeds rarely over 65, that means 5th gear with 3.42 diff and stock rubber.

 

Funny thing is, my '98 Chevy 2500 with 454 V8 and 4.11 diffs, I got the same good results at 1800-2200 RPM and the fuel economy was on almost as good as what I am getting with the 2013 5.3L I have now. It is a crying shame that GM could not get a small block better fuel economy than a big block from over a decade ago. Seems like the R&D boys are goofing up on the job.

Edited August 25, 2014 by Cowpie