Final Drive Ratio

[Wangspeed]

I assume that by going from 3.82 -> 4.05 that I should change the FD ratio from 1:1 to .94:1. Is this right, or did I get it backwards?

The help file wasn't very helpful for this. I wasn't expecting to see 1:1 there, but I suppose it makes sense, since there's no way to tell which one the car comes with.

[Wangspeed]

Also, if someone else has access to an HHR tune, would you see how many VSS pulses per mile it is set to?

[Iam Broke]

26715 ppm Cobalt/ 25933 HHR is 1.03015463

I would leave the ratio at 1.00 and just change the ppm. Changing both would cancel it IMO but I've never tried it.

[Wangspeed]

26715 ppm Cobalt/ 25933 HHR is 1.03015463

I would leave the ratio at 1.00 and just change the ppm. Changing both would cancel it IMO but I've never tried it.

Thanks for the info. Still a little confused about the ratio though. I would think it would be either .94:1 or 1.06:1. Stock HHR SS has 1.03 and lower PPM? Totally confused on that. I would have expected higher.

Just swapped it to 1:1 and 25933, as you suggested. I would think I could use stock HHR settings though. Or an LSJ, if they have the same tire sizes.

[Iam Broke]

I forgot about the different tire size coming into play with the total ratio. No LSJ tunes here for me to check. Sorry if I misled you.

[LNFnewb]

If anything wouldn't the HHR be higher? so 1.06:1 rather then .94:1?

1.06:1 is like 3180(HHR) : 3000(SS/TC) when you translate the ratio to RPMs. While .94:1 is like 2820(HHR) : 3000(SS/TC)?

[Wangspeed]

Interwebz has failed me.

Which number is which? If they're not talking about actual gear ratios, I don't know if the first or second number represents the stock value.

[Wangspeed]

Tom do you have an HHR file you can send me?

[Iam Broke]

Done.

[Area47]

it's different in all three years. i pulled up a 10 file last night that had 3.83 in it, and an 09 that had a 1.0:1 in it for the fd.

[Iam Broke]

He has an '08 & '09 file to look at now.

[Wangspeed]

So, according to GPS, 26715 ppm is the right VSS setting. As far as the FD ratio, I changed it to 4.05, and there seem to be no ill effects. The HHR SS GMPP tune has 1:1 in it, but the VSS is set lower. Doesn't make sense to me, unless they come with taller tires, but I thought they were also 225/45-18.

Not sure if the change in the FD setting is actually doing anything for me. No chance to log any decent WOT runs.

[Iam Broke]

2008 HHR SS had 225/45-18's from what I found online. That doesn't mean the speedo was correct. Most are off 2 mph or so at 60. I use the GPS to cal mine also.