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Discussion Starter · #1 ·
yeah, yeah, yeah, I've searched till I'm blue in the face, but can't find how to determine the posi ratio in the Fatwudy WITHOUT jacking it up.

It's a '95 Estate Wagon with posi. And I'm assuming it's the stock, original differential. Is that right, Bill?

I didn't get home from the gig until 3am, and I don't feel like jacking it up, putting it on stands, turning the wheels, counting the yoke, etc. etc.

And I tried to read the faded SPIL codes. Looks like a G80 is showing.

Any shortcuts for my tired, lazy ass on a Sunday afternoon?

[ 04-22-2007, 09:00 PM: Message edited by: doc540 ]

Discussion Starter · #4 ·
A G80 94-96 wagon as best as I know means 2.93s. They were available with 2.56 but not in combination with G80.

Discussion Starter · #5 ·
Best is probably to determine if the car had the towing option (V08 HD cooling with mechanical fan, which means 2.93 ratio), or dual electric fans (2.56 ratio)--very easy to figure out. This is in lieu of what codes can't be read on the SPIL.

95 FSM says: (and 96 is the same)

without G80, only ratio available was 2.56

with G80, either 2.56 (RPO GM8) or 2.93 (RPO GW9) ratio was available

Discussion Starter · #6 ·
got a tach? if so put in 3rd(1:1) and record rpm at a given speed and input to the calculator at

Discussion Starter · #9 ·
thanks, I pm'ed him earlier.

It had a mechanical fan before Bill did the delete/electric conversion, so 2.93 sounds plausible.

At 70mph it has a GREAT passing gear. MrsDoc and I cruised down to the beach and back, and on that narrow, Texas two lane it hopped around traffic like a jackrabbit.

Discussion Starter · #12 ·
I started typing out instructions earlier but got stumped on one button so I had to go do it to be sure.

press and hold "off" and "temp up" at the same time till the whole display lights up in jiberish, once that settles down and there are two "00" for temp press "fan up" till you get "06" to display and then hit "middle".

It will display tach as "08" for 800rpms "21" for 2100rpms etc.

I forget who posted that here a few years ago but I like to play with it.
Simply hit "auto" to get it to back to normal mode.
I really do not know how accurate it is though I think it should be good since it is a digital display driven by the pcm.

Discussion Starter · #13 ·
Worked like a charm.

At full throttle it shifted out of first at about 5400, and in third gear it was turning 2100 at 60mph. That calculates to a 2.93 gear ratio using the links below.

Then at 60mph it was only cruising 1400 rpm in overdrive.


btw: Here's a link to determining gear ratio:
Fill in the data and PRESTO RATIO!

And here's a tire data calculator
Need Tire Data?

[ 04-22-2007, 09:55 PM: Message edited by: doc540 ]

Discussion Starter · #14 ·
I wish I remebered who to give credit too. I read about that on forum a couple years ago shortly after I bought the wagon.
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