Vin help

[Marcus]

Have a 1981 GMC Jimmy with the vin ID of 1GTEK18D7BF509290 . Can’t find anything that will decode the vin to find out what gears it has. Not going to pay $20 to get the info from a website. Was hoping to do it the easier way instead of having to take things apart. Any good information would be greatly appreciated!

 

[CSFJ]

There's nothing in the vin that will give you axle ratio. If the rpo codes aren't in the glovebox, or underhood, you'll need to pull a diff cover and get the numbers off of the ring gear.

 

[Keith Seymore]

There's nothing in the vin that will give you axle ratio. If the rpo codes aren't in the glovebox, or underhood, you'll need to pull a diff cover and get the numbers off of the ring gear.

This is absolutely correct.

K

 

[HotRodPC]

Of it's not been changed, the code on the axle tube can tell you. The codes are listed in the Squarebody Library. Best it to always pull the cover, or jack it up, spin the rear tire and count the driveshaft turns.

 

[Marcus]

Okay that’s what I was afraid of. Thanks guys. The glove box is missing all together and nothing under the hood or on the door jam. Gonna have to do it the hard way.

 

[yevgenievich]

Mark drive shaft and spin the tire to get a good estimate. If only one rear tire off the ground and open rear then divide the wheel rotation by 2.

 

[HotRodPC]

Mark drive shaft and spin the tire to get a good estimate. If only one rear tire off the ground and open rear then divide the wheel rotation by 2.

Exactly, This is just as accurate as pulling the rear cover. There's also a thread in the Diff section for using this method in detail.

 

[roundhouse]

Always a good idea to pull the cover anyway

You never know what you’re gonna find

Usually some loose teeth or something laying in the bottom

 

[Marcus]

Well I know the vehicle and the person who owns it so I know it’s works as well as the front axle. We just don’t know the ratio right now but I will be finding out soon. Trying to get a 3.42 to put in my truck build to make my rear match the front for now. Will be going to switch both out to a 3.73 as soon as I can afford to do it.

 

[HotRodPC]

How soon are you looking to do this? Is the truck broke down now? Have you considered a 3/4 ton axle upgrade? I may have a 14 bolt Semi Float for sale sometime this summer with 3.42's in it. You'd have to use a combo U joint, acquire 8 lug wheels and tires and convert your front rotors and hubs to 8 lug. There is no such thing as a factory 14b Full Float in 3.42's, but there is in 3.73. Maybe more of a worthy conversion when you go to 3.73's. Maybe even find a set of 3/4 ton 3.73 axles.

 

[Marcus]

How soon are you looking to do this? Is the truck broke down now? Have you considered a 3/4 ton axle upgrade? I may have a 14 bolt Semi Float for sale sometime this summer with 3.42's in it. You'd have to use a combo U joint, acquire 8 lug wheels and tires and convert your front rotors and hubs to 8 lug. There is no such thing as a factory 14b Full Float in 3.42's, but there is in 3.73. Maybe more of a worthy conversion when you go to 3.73's. Maybe even find a set of 3/4 ton 3.73 axles.

I don’t want 3/4 ton axles. I appreciate it though. I’m getting it ready to drive daily for now. Eventually I’m going to restore it to somewhat factory and make it look good. It was my grandpas truck and then my uncles high school truck so it’s something special. Wanna keep it as close to factory as possible. Just want better gears.

 

[Marcus]

There's nothing in the vin that will give you axle ratio. If the rpo codes aren't in the glovebox, or underhood, you'll need to pull a diff cover and get the numbers off of the ring gear.

The rear end is stamped GM9 on drivers side. Stamped 9969 on passenger side. 06LT on passenger side up top.

 

[Marcus]

Mark drive shaft and spin the tire to get a good estimate. If only one rear tire off the ground and open rear then divide the wheel rotation by 2.

Ring gear has 4018121 12 41 1280 on it. This means 3.42 right?

 

[yevgenievich]

Ring gear has 4018121 12 41 1280 on it. This means 3.42 right?

Yes

 

[Marcus]

Yes

Thank you. Just wanted to double check with a few people before I went ahead