Video of C8 Corvette Acceleration on a Detroit Highway

[P-Tree]

I appreciate the discourse and links / documentation of information that furthers the discourse and discussion. It's quite helpful if you readily know where the information is to link to it or post it up so that others may read it and be informed.

[Bikerjulio]

Having 8 speeds is where the ZF rumor started since only ZF have publicly announced an 8 speed DCT. That R&T writer did one lazy google search and never clicked beyond the first page of results.

This discussion has been going on for a year and a half now, ever since the first CAD images leak. We have never had confirmation of the provenance or date on the CAD image showing a ZF trans. It's quite possible that GM looked at a ZF trans in the early stages, but authoritative sources like Don Sherman have stated it's Tremec, as well as there being plenty of other evidence like the presentation photo above, and the investment that Tremec has made in the US. All will be settled at the reveal. Thank goodness.

Google works differently for different people, but my search turned up the C&D piece on P1.

[electroVette]

Oh, that's right, one of the CAD images does show a ZF transaxle. Another image shows a different transaxle. Maybe they designed for both so if Tremec ran into issues the ZF could be used?

[Klinn]

If the thesis above posted above that adding more gears overrides any gains made in performance and efficiency, why did Corvette not stay with the 2014 six speed automatic transmission, and why is GM for its Camaro, pickups and SUV’s now increasingly going to ten speeds?

I didn't mean to imply that adding more gears is *never* worth it, just that at some level we'll be reaching the point of diminishing returns.

Dunno where that point lies, and I guess it must vary depending on the application. As an extreme example, consider commercial trucks with 18-speed transmissions to compensate for their narrow power band. Cars, and Corvettes in particular, have a much wider power band and I'd be surprised if our transmissions ever get to that level of complexity.

[Bikerjulio]

Oh, that's right, one of the CAD images does show a ZF transaxle. Another image shows a different transaxle. Maybe they designed for both so if Tremec ran into issues the ZF could be used?

GM would have had to sort out the major dimensions of the transmission package very early on, so it's reasonable to think they would have looked at what options were available at the time (whenever that was), and done some virtual test fits, in order to come up with a set of specifications for the new trans. And then given them to Tremec.

[Maxster]

As to Corvettes alone, we have seen the Corvette go from four gears, to six gears and starting in 2015 to eight gears.

Here’s GM latest press release on going to eight gears on the Corvette with it explicitly noting the efficiencies of adding more gears to the Corvette’s auto trans.

It seems that your question is addressed to Klinn but without being a fuel economy expert by any means, I will chime in. The narrower a rev band for a given engine, the more gears that are needed. The past and current Corvette engines with lots of torque at low rpm do not need more than 6 gears including one for comfortable cruising IMHO. Is the C-8 coming with a high revving engine with no beans in the low end? Possible but not probable. Automatic transmissions may be better suited for multiple gears

[electroVette]

GM would have had to sort out the major dimensions of the transmission package very early on, so it's reasonable to think they would have looked at what options were available at the time (whenever that was), and done some virtual test fits, in order to come up with a set of specifications for the new trans. And then given them to Tremec.

Too bad that slide doesn't have a clearer view of Tremec's transaxle so we could compare it to the ones from the CAD images. Not that it's so hard to wait a few more weeks - but I kind of like solving the riddle.

[Maxster]

Too bad that slide doesn't have a clearer view of Tremec's transaxle so we could compare it to the ones from the CAD images. Not that it's so hard to wait a few more weeks - but I kind of like solving the riddle.

I would think that the Tremec make$ more $en$e than the ZF.

[Bikerjulio]

It seems that your question is addressed to Klinn but without being a fuel economy expert by any means, I will chime in. The narrower a rev ban for a given engine, the more gears that are needed. The past and current Corvette engines with lots of torque at low rpm do not need more than 6 gears including one for comfortable cruising IMHO. Is the C-8 coming with a high revving engine with no beans in the low end? Possible but not probable. Automatic transmissions may be better suited for multiple gears

I'm agreeing with you. My C6 has 6 speeds and that's plenty for a manual trans matched to that engine. 3rd will get me well into 'arrest me" territory here. I rarely use 6th as well. Any more than 6 and it's a PITA in a manual IMO.

The GM marketing piece on the 8-speed is not convincing to me. Maybe they get better "highway mileage" but it's not because it has 8 speeds. That rating is at a steady 70 MPH and any speed trans could be configured with the same final drive ratio.

I'll accept that there must be some mileage advantage with 7, 8 or 10 speeds, but then an auto trans almost becomes a requirement as well.