Weird News!

"G_Body_Man: Sponsored by the number 3" (gbodyman)
04/22/2015 at 11:14 • Filed to: None

So I was going through RPO codes yesterday evening, and I found out some interesting stuff. My car is a sedan with the F41 Firm Ride and Handling Package. It also has land-speed record gearing (2.21s, IIRC), and an open diff (sad face). However, it is pretty cool that it has the F41 pack. Next up after a dual-snorkel air cleaner is a G80 and 2.73s!

DISCUSSION (22)

TheVancen- In Pursuit of a Greater Payday and Car Parts > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:18

Why just 2:73s? Why not go higher, like a 3:25 or 3:50? And what is the car again?

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:19

2.21... you know a Jag V12 XJS in this country was no taller than 2.88, right? That in a sharp turn, a 2.21 has the inside wheel going less than twice as fast as the input shaft? What the hell is your first gear in the box - 4.8:1?

G_Body_Man: Sponsored by the number 3 > RamblinRover Luxury-Yacht
04/22/2015 at 11:30

I have no idea. It’s something insane. My friend literally spat cereal across the room when I messaged him about my gearing.

G_Body_Man: Sponsored by the number 3 > TheVancen- In Pursuit of a Greater Payday and Car Parts
04/22/2015 at 11:31

1984 Cutlass Supreme. I would go higher, but I want decent fuel mileage. I could stretch to something like a 3:27.

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:33

My Ranchero was optioned in completely the opposite direction. It had a special order 9-code rear end, which is to say, a 4.10. With 13” wheels and tiny bias plies, because wheezy 144 six. HURR. I never drove it that way since the engine (and floorboards) were out when I got it, but wowzers.

TheVancen- In Pursuit of a Greater Payday and Car Parts > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:34

Ahh, I see. Make sure you change the speedometer drive gear as well.

G_Body_Man: Sponsored by the number 3 > TheVancen- In Pursuit of a Greater Payday and Car Parts
04/22/2015 at 11:36

I shall!

G_Body_Man: Sponsored by the number 3 > RamblinRover Luxury-Yacht
04/22/2015 at 11:36

I know. I didn’t even know they made gearing that long!

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:41

The pinion gear from my Jag 2.88 is the size of a fist, yours must look absolutely ridiculous out of the case. I just searched, though, and it seems GM weren’t the only ones to make a 2.21 diff - Jeep/AMC used a Dana 35 one in some models.

G_Body_Man: Sponsored by the number 3 > RamblinRover Luxury-Yacht
04/22/2015 at 11:43

Yup. I have the 7.5 10-bolt. A diff that’s perfectly fine until you actively start trying to break things.

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 11:46

If, on the other hand, I had tried to run that 4.10 Ford 7-1/4” with anything over a hundred horsepower, it probably would have cracked like a walnut. Low gearing and a teensy tiny flimsy eco-car case is a recipe for disaster.

G_Body_Man: Sponsored by the number 3 > RamblinRover Luxury-Yacht
04/22/2015 at 11:52

Wow. I didn’t even know they made rear diffs that small.

crowmolly > RamblinRover Luxury-Yacht
04/22/2015 at 11:57

You oughta see the 2.75 gears I have for a Ford 9”.

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 12:01

Kinja'd!!!

Here’s one compared to a Ford 8”. Not much there, and at that ratio compared to yours, double the lateral load on the pinion for every ft-lb of torque.

G_Body_Man: Sponsored by the number 3 > RamblinRover Luxury-Yacht
04/22/2015 at 12:03

It’s tiny!

RamblinRover Luxury-Yacht > crowmolly
04/22/2015 at 12:04

Probably pretty close, +10-15%. The Dana 44’s Grandpappy that the Jag uses isn’t a small diff.

crowmolly > G_Body_Man: Sponsored by the number 3
04/22/2015 at 12:04

Go with at least 3.08 gears with a 3 speed auto, 3.42 gears with a 4 speed auto. You will be pissing money away having a rear end done for 2.73s.

RamblinRover Luxury-Yacht > G_Body_Man: Sponsored by the number 3
04/22/2015 at 12:06

It was under a “Truck” that was cargo-rated to 800lb. I guess as long as you don’t have any engine power whatsoever...

G_Body_Man: Sponsored by the number 3 > crowmolly
04/22/2015 at 12:08

Thanks for the tip! I’ll probably go with 3:27s.

RamblinRover Luxury-Yacht > crowmolly
04/22/2015 at 12:11

I think he’s been digging that magical “305 at maximum strain” mileage. I wouldn’t have gone with the 2.88 myself in my project except that it was cheap and my 1st gear in the trans made up for it. 2.73 is still kind of stupid tall.

Snuze: Needs another Swede > G_Body_Man: Sponsored by the number 3
04/22/2015 at 12:13

3.08 was a popular rear in a lot of older GMs. It would be a huge improvement over your 2.21 and not quite as thirsty as the 3.27. My dad had a 3.08 in his 86 Caprice. With a built 350 it would have no problem spinning the rear tires, and still returned decent fuel economy

G_Body_Man: Sponsored by the number 3 > Snuze: Needs another Swede
04/22/2015 at 12:17

I’ll take photos of RPO codes when I visit the junkyard.