ok so i have a 1986 camaro iroz 5.0 tpi. I was wondering as to what my gear ratio was. SO i downloaded the rpo decoder. went outside and took off my lid to the arm rest came back in and started throwing codes at it. I started to get suspicious when it said i was suppose to have ttops, and its obvisouly a hard. So i threw the vin into car fax and got that my arm rest is out of a 1984 camaro. So now im pisssed off. but as i say better to be pissed off than pissed on. While looking on here earlier today i saw where some guy said that he could take a vin and get the right rpo codes. Now i cant find this. Can some one please help this noob thirdgener in distress? thanks
nate

 

Even with the right rpo codes, the gears could've been changed. Jack it up and spin the tires.

 

i realize they could of been changed, but i would know what else my car came with. spinning the tires will only tell me that i have or dont have posi , which i already know i dont.

 

If the rear axle is stock it probably has 3.23's or 3.42's. To find out for sure you can jack the rear of the car up. crawl under the car and have someone spin the rear tire one revolution and count how many times the driveshaft moves in a complete revolution. you might want to mark the driveshaft with tape or a marker. Then for arguments sake it spun around 3 times that would give you a 3.00 rear gear ratio. To give you a good idea hear the gear possibilities are 2.73, 3.08, 3.23, 3.42. if it doesn't come around the third time you have 2.73's. if it is just a hair over 3 turns you have 3.08. If it goes almost a quarter turn past three you have 3.23. If it goes half way past 3 you have 3.42. Hope it helps.

 

thanks for the help, its freezing right now and cant get outside though. ill try it this spring

 

When checking out the SPID decal (with all the RPO codes on it) the very first thing to check is to compare the VIN on the SPID with the VIN on your car. They must match. If they don't, then the all the RPO's are meaningless and pointless.

It sucks when it's incorrect, but with our rides getting older and very few being 1 owner cars, anything can happen.

I'm not sure where your from, but in Canada (at least a couple years ago) you could take your VIN to the local Chevy dealer and they would run it and give you a complete list of your RPO's and what they stood for (free of charge). I picked one up like that. Not sure if they still do or in the US.

 

Here's how to determinne your ratio (jerk the diff cover and look): numbers are stamped on the ring and pinion:

41 : 15 = 2.73
41 : 14 = 2.93
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC