F35 or F23... How do I know which one I have?

PaulPerger

PaulPerger

Well-Known Member
I just went through all of the options on the order page and I am seeing that you now have to declare which transmission you have. I don't remember this being required before, but it's been a year since I looked, so I probably just don't remember this.

I thought it would be easy, as I have the G85 which has the LSD which I assumed was the difference but in researching this I have found that both the F23 and the F35 can have the LSD option. So, how can I tell which Transmission I have?

My donor is a 2006 SS/SC.
 
A

Andrewlee92

Active Member
F23s came in base and sport models. F35s Only come in the Supercharged and turbocharged Cobalts. And then ypu having G85 package means LSD and Recaro seats. For the 05 and 06 year then they dropped the Recaros for 08 to 10 and was just LSD
 
PaulPerger

PaulPerger

Well-Known Member
Thanks. That confirms what I thought. Sometimes web surfing can be very confusing.. I probably read something that wasn't true and it got into my head and started messing with my memory!
 
S

Scott #321

Well-Known Member
All mentions of f23 having LSD are aftermarket upgrades as the trans was not offered from the factory that way. Major bummer as there are no salvage f23 LSD's to be had.
 
PaulPerger

PaulPerger

Well-Known Member
Can the Factory LSD From the F35 be installed in the F23?

I am reading that the F23 is much stronger. I have the F35 with the LSD. If I can order the F23 from DF, I think it might be worth the $500, but I don't want to lose the LSD...
 
Rauq

Rauq

Goblin Guru
The F35 diff can't be installed in an F23.

Your options are an LSD insert, about $250 but not particularly effective, an OBX helical LSD, about $500, or a Quaife helical LSD, which is normally about $1000. Both the Quaife and OBX are a similar style LSD to the factory (but optional) F35 LSD. The OBX is not of the same quality as the Quaife, but you can buy a hardware package for the OBX that is said to close the quality gap to some extent.
 
Ross

Ross

Goblin Guru
Rauq said:
The F35 diff can't be installed in an F23.

Your options are an LSD insert, about $250 but not particularly effective, an OBX helical LSD, about $500, or a Quaife helical LSD, which is normally about $1000. Both the Quaife and OBX are a similar style LSD to the factory (but optional) F35 LSD. The OBX is not of the same quality as the Quaife, but you can buy a hardware package for the OBX that is said to close the quality gap to some extent.
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Really? I thought most GM LSDs have clutch packs, not helical cut gears. They work on different principles. Does someone know what kind of LSD is in the stock G85 equiped F35 transmission?

Well, ssyellow says you are correct:
The G85 is a ATB diff from quaife (ATB = Autmatic Torque-Bias)

I wonder if the G85 has the exact same differential that I can buy from Quaife, or if it was a custom version only made for GM?
 
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Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
PaulPerger said:
Can the Factory LSD From the F35 be installed in the F23?

I am reading that the F23 is much stronger. I have the F35 with the LSD. If I can order the F23 from DF, I think it might be worth the $500, but I don't want to lose the LSD...
Click to expand...
This is just my engineering opinion:
The design of the GM transmission designations is an indicator of the relative strength - rated in Newton Meters.
The F23 is 230Nm or 170Ft.lb.
The F35 is 350Nm or 260Ft.lb.
The F40 is 400Nm or 300Ft.lb.

Also keep in mind these ratings are based on the relative size vehicle they were designed to be installed in: the F23 in subcompact to compacts (@3000lbs), the F35 in compacts to midsized (@3500lbs.), and F40 in midsized to lower end full size cars (@4000lbs.) - which are incrementally heavier which in turn makes the torque rating also incrementally larger when installed into the same weight vehicle (like Goblin).

In a rough estimatation, based on my flawed thinking, a Goblin weighs 1800lbs. (estimate with driver) or 60% the weight of a subcompact/compact - or 52% the weight of a compact/midsize - or 45% the weight of a midsize/full size. Using these estimates I come up with the following Goblin torque numbers that align with the design factors advertised for the GM transmissions:
F23 - 170Ft.lb. X 40% = 240Ft.lb.
F35 - 260Ft.lb. X 48% = 385Ft.lb.
F40 - 300Ft.lb. X 55% = 465Ft.lb.

Obviously the real world numbers for the GM transmissions, based on the experiences of many Goblin drivers and other Ecotec built vehicles, indicates these numbers are very conservative. But the GM design numbers can also be thought of as a value to base the expected longevity of each transmission installed on an identically built Ecotec. Yes, the transmission can handle the torque, but will it last 5000 miles, 20,000 miles, 100,000 miles?

There are so many factors that play nto this equation that you should probably base your decision on what your budgeted for. :D
 
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Desert Sasqwatch

Desert Sasqwatch

Goblin Guru
Turning with 100TW tires will likely tear up the axle CV joints, since those seem to be the most likely weak point in a (mostly) rigid drivetrain - if the spiders are welded. But great if you're only drag racing and not turning much. ;):cool:
 
Sluggonaut

Sluggonaut

Goblin Guru
I'm not sure which saying is more appropriate here - "Send it" or "Eff around and find out"?

Either way, I am curious about the results.
 
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