i have had this 1985 trans am since 1988. it cost 19,400$ brand new in 1985. (i found the original bill of sale the other day). i was looking under it today and counted the bolts on the diff. 9. why did i not notice this beore? well i am hoping someone can confirm this is a good diff. the tags on it says:
P/N 10032270
RATIO 327

other tag
SPIN RESISTANT
DFF
USE APPROVED LUBE ONLY
SER#6965

the car has not been driven since 1993-94 so its fairly rust free.

 

just ran the codes from the glove box. GW6 G80 J65

 

Well the 3:27 gear ratio makes it a BW 9-bolt with limited slip and rear discs brakes. Firebirds used the BW 9-bolt rear a couple of years before the Camaro.

 

The rubber plug in the back cover also determines that it's a 9 bolt.

There were no 9 bolts available in 1985 or if there were, there's very little documentation on them.

What's the 10th digit of the VIN code? Can you find a build date. It's possible it was a late 85 build making it a 86. 1985 will have F for the 10th digit. 1986 will be G. The new year starts Sept 1 so a car made after Sept 1 1985 will be classified as a 1986.

 

there was that look at the tech data on the web site

 

the car was sold may 16 1985. the vin is 1G2FW87H5FN229XXX .
here are some more pics of it in my backyard. i parked it in 93 because it was in mint condition and i didnt want anything to happen to it. original paint not one dent. well i lost the garage spot so it sat outside. now it needs full resto.





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the dash is in canadian kilometers

 

Vin code confirms it's a 1985. The first digit 1 indicates it was US made so it's considered a export to Canada based on the metric gauges. Somewhere in the RPO codes it will say that.

That's a rare option to get the 9 bolt diff in a 1985.

 

My 85 had a 3.27 9-bolt as well. 10th digit in my vin is a F as well. When the posi started going out I swapped for a ls1 10-bolt.

 

they also had the 3.70 9 bolt in the L69 TAs as well

 

I've had two '85s with 9bolts....

 

My moms 85 Trans Am has drum brake 9 bolt rear under it.

 

'85 was the first year for 9-bolts in Firebirds. '87 was the first year for 9-bolts in Camaros.

 

My reply in the second Post.

 

the dash isnt in kilometers its in miles an hour, if it were a canadian car the kilometers would be the ones on the outside of the miles not the other way around...and kilometers would be the one in bold at the bottom of the speedo
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so i take it all cars before say mid 85 had 8 bolt rear ends?? mines 84 H.O. with a 3.73 possie and rear disk , what should it have for a rear end guys?

 

10-bolt 7.5 dia gear.

 

nice try but it is CDN car. Being a 85 model the speedos all read 140 KM/H or 85 MPH.

So we see 140--and it has to be kms

86's saw the 140mph ones come back.

 

my mistake, i can see now what your talking about. my 1984 has a 140mph speedo but it was changed as i have the stock one..growing up my buddy in highschool had a 83 Z28 and it had a speedo well into the 200+klm i dont remember exactly but i think it went to 240 klm and i know we burried it a few times.. i cant believe they had a 140klm speedo ...these are supposed to be sports cars...LOL... ,
thats why i love this site..learn something new every day

 

my understanding was the 140kilometer speedo was government mandated. not sure if this is correct.

 

well the 85MPH speedo was by US lawmakers. Canadian divisons of the automakers just went along with it.