5th doesn't look right... otherwise we've got a theoretical top speed of about a bajillion mph.

Here's the math on drive ratio per gear--

1st = 3.38 = 13.689
2nd = 1.76 = 7.128
3rd = 1.18 = 4.779
4th = 0.89 = 3.6045
5th = 0.07 (??) = .2835 (??)

Final = 4.05:1



1st = 2.96 = 9.7384
2nd = 1.62 = 5.3298
3rd = 1.00 = 3.29
4th = .68 = 2.2372

Final 3.29:1

 

5th = 0.7

 

Transmissions
GM Powertrain Sweden F35 5-speed manual / Hydra-Matic 4T45 4-speed automatic
Gear ratios: (:1):
First: 3.58 / 2.95
Second: 2.02 / 1.62
Third: 1.35 / 1.00
Fourth: 0.98 / 0.68
Fifth: 0.69 / –
Reverse: 3.31 / 2.14
Final drive ratio: 4.17:1 / 3.29:1
https://www.chevyhhr.net/forums/hhr-ss-45/2008-hhr-ss-frequently-asked-questions-9989/

 

You would need a flux capacitor which could produce 1.21 gigawatts of electrical power to obtain those speeds. I can't remember where I heard that.

 

Are you sure those are the correct numbers? Check out http://media.gm.com/us/powertrain/en...08/08truck.htm. Check out the spec sheets for the LNF's transmissions, both 4T45(MN5) and F35(MU3).

4T45/MN5 shows:
First: 2.96
Second: 1.62
Third: 1.00
Fourth: 0.68
Reverse: 2.14
Final Drive Ratio: 3.05, 3.29

F35/MU3 shows:
Gear ratios: MU3
First: 3.38
Second: 1.76
Third: 1.18
Fourth: 0.89
Fifth: 0.7
Reverse: 3.17
Final Drive Ratio: HHR SS - 4.05

 

One must remember that you have to multiply the final drive ratio by the transmission ratio to get the OVERALL ratio, IE: 4.05 final drive by .7 5th gear = 2.835

Example MPH x GEAR RATIO x 336 / TIRE DIAMETER = RPM
60 x 4.05 x .7 x 336 / 25.25" = 2263 RPM @60 MPH
(4.05 x .7 = 2.835 overall Gear Ratio)

 

Like I did in my post above?

Either that, or a darned good intercooler on the La Machine.

 

at what mph does the auto shift for each gear at normal acceleration occur

 

Well, it really all depends on your idea of normal...

 

as in traffic