Long story short, I have an F35 w/ LSD out of an '10 Cobalt SS TC and picked up an M86 F23 out of an '08 HHR w/ 4.17 final drive.

To some this could be a fairly stupid question, but can I use the LSD out of the F35 and put it into the M86 F23?

I know there is the Quaife, OBX, and inserts but i'd rather use what i have than shell out $1k for the aftermarket LSD and sell the F35 w/ LSD.

 

No. They're completely different sizes.

Quaife tech specs for the F23 diff: https://shop.quaife.co.uk/media/blfa_files/QDF17B.pdf

Quaife tech specs for the F35 diff: https://shop.quaife.co.uk/media/blfa_files/QDH8J.pdf

I bet you could sell that F35 w/ LSD for close to what the aftermarket LSD would cost though. It's a bit undesirable to those in the know because of the 3.82 final drive, but the LSD makes up for that.

That's essentially the route that I'm looking to go. HHR trans with Quaife LSD.

 

Well shyit ..... i appreciate you looking into this!

 

I have a non-LSD 3.82 with less than 50K miles that's available. Was pulled from one of my sedans that was totaled.

 

Finally got this F23 installed and I'm a huge fan of this swap! Only issue I'm having now is the speedometer is way off. For the most part it will not go over 20mph. I have HPTuners and have changed the FD to 4.17 and the vss pulses to be the correct number and that did not help. I also tried the F35 speed sensor in place of the F23 speed sensor and that did not make a difference.

Do I need to wire in something? Any help here would be much appreciated!

I'm using vss pulses per mile of 72,616.13 given i'm using the 4.17 fd F23 speedo ring which is supposed to have 29 teeth on a Quaife LSD with 285/35/19 tire



similar issue: https://www.cobaltss.net/forums/prob...ed-lsj-326108/

@USMCFieldMP Any insight?

 

Who needs a speedometer. Use the tach No in all seriousness USMCfieldMP should chime and be able to help.

 

72616 pulses/mile seems way too large. Let me run some numbers.

EDIT: I think you should be in the 23,316 ballpark. What size tires are you running?

Important to note that every brand's tires have different dimensions and the amount of pressure in your tires will change their diameter, too.

[ 1 mile (63360 inches) / circumference of tire (Pi x Diameter - stock 225/40-18 is 78.8") ] x [ Number of pulses per revolution ] = VSS Pulses Per Mile

63360" / 78.8" = 804 rev/mile (a 235/40 should be 794 rev/mile; 245/35 is 815; 245/40 is 785)

804 rev/mile x 29 VSS pulses/rev = 23,316 VSS Pulses/mile


Based on that, your speedo is currently showing you a third of what your actual speed is. So you're doing 60, and it says 20.

 

THANK YOU SO MUCH! I have 285/35/19 tires which means I should be at 17,413 vss pulses per mile. I don't know if this is allowed but I have created a spreadsheet for these calcs. There was another link which I'll post below where I got the 72k vss pulses. I'll try 17,413 and get back.

VSS Pulse Calc




https://forum.hptuners.com/showthrea...The-Fix-Thread

 

I think the math in your spreadsheet is off. 285/35R19 should have a diameter of about 26.9", circumference of ~84.5", for a Rev/Mile of 749.

Which gives 21,721 pulses/mile.

I always double check my sizing here: https://tiresize.com/calculator/

TireRack also typically has a pretty good listing of specific tires' diameters and Rev/Mile information in their specifications section.



EDIT:

Some calcs:

285 mm x 0.35 = 99.75 mm [Sidewall height]

(99.75 mm x 2) / 25.4 in/mm = 7.85 in [Total sidewall height]

7.85" + 19" = 26.85" [Tire Diameter]

26.85" x Pi = 84.35" [Tire Circumference]

63360 in/mile / 84.35 in = 751 revs/mile

 

I was making this harder than it needed to be - tiresize.com was a perfect resource for my exact tire on revs/mile (which was 773 on 285/35R19 R888R's). 773 * 29 = 22,417. I input 22,417 into vss pulses / mile in HPTuners and wouldn't you know it... works like a champ.

You are a gentleman and a scholar.

 

Awesome, glad it worked out. This was actually a good reminder for me, since I'm hoping to have my F23-swapped car running soon. I had totally forgotten that I was going to have to adjust the VSS.