FatTireBiker

Thanks guys

2005HHRauto

Well, I finally figured out why the HHR SS automatic axles are unique to only the HHR SS automatic 'buggys'.

It's all about TORQUE STEER.
https://en.wikipedia.org/wiki/Torque_steer
https://www.matfoundrygroup.com/blog...s_Torque_Steer

I recently read some articles about the development of the HHR SS, & the engineers were really really concerned about controling torque steer.
That's why they didn't use off-the-shelf axles that were maybe plus or minus a half inch or so.

The exact size of the HHR SS automatic axle was the best size for the least amount of torque steer.
So, if you are using replacement axles that are not exactly the same as the stock axle, you will increase the amount of torque steer.

And that also explains why the engineers reduced the power output of the automatic HHR SS, as that is the best way to reduce torque steer.

GM states that they reduced the power output of the automatic HHR SS to 'save' the transmission.
But I know that this isn't true, as I have been running way more power thru my automatic for 15 years now with no issues.
In fact, at my last time at the track I had my best trap speed of almost 114 mph.

But I do have wicked torque steer, & I really really have to hold-on-tight, & man-handle the steering wheel when I go crazy on the street.
That's the real reason that GM reduced the power output of our automatic HHR SS 'buggys', to reduce torque steer.
They had to reduce the power as there would be many many wrecked automatic HHR SS in the 'bone' yards.

As you can see GM reduced power up to 37% in the stock 'tune'
With the GM Performance GMS1 'tune' they make you 'pay' to have 'full' power. LOL

Columns 0 & 7 are park & neutral & columns 1-4 = 1st thru fourth gears, & column 5 is not used with the automatic 'tune'.

Stock HHR SS automatic



GM Performance Stage1 GMS1

Oldblue

That and the SS hub has different splines from the LS/ LT hubs

2005HHRauto

More spines = stronger axle to handle more torque.

GM had small platform = Cobalt , HHR
Medium platform = Malibu, Malibu Maxx
Large platform = Impala

To upgrade the HHR to SS = using stronger parts from the medium platform.
Axle type & brakes are from the medium platform.
Power came from the new LNF engine.
Suspension was newly developed just for the SS.

GM felt very strongly about the SS meeting 3 requirements.
1. Had to have more power
2. Had to handle better.
3. Had to brake better.

Oldblue

I think they covered all the bases, just sad the economy tanked in 2008 and a fun SS was only available for 3 years.

2005HHRauto

American engineering couldn't figure out how to control torque steer.
It took Japanese engineering.