spid decoding

[rich67]

can u tell from the code what gear ratio the posi unit is? code is 4G80AA posi traction A

[hugger6933]

The code for a posi unit is G80[ or at least it is in the newer stuff, probably the same for the older stuff as well]. The rear end ratio comes from the ring gear and pinion not the positrac unit. That is where the term ratio is coined for this comes in the ratio of the drive gear [that would be the pinion] vs. the driven gear [ that would be the ring gear]. Depending on what engine you had, the standard ratio gears or the optional gear[but if they were optional they would be listed on the spid. I know that I read earlier this week that with standard V-8 and 3or 4 speed the 70 model [that what I'm working on this week so that is all that matters to me right now, right?] is 3:73 to 1. I found that info @gmheritagecenter.com go there and check out your year model. Jim

[rich67]

wont have to jim. its a 70 gmc 1/2t. so from what i gather from your post if it was other than the standard 373s it would be listed on the spid. special order. correc? and thanx for your input, rich

[Keith Seymore]

Originally Posted by rich67

wont have to jim. its a 70 gmc 1/2t. so from what i gather from your post if it was other than the standard 373s it would be listed on the spid. special order. correc? and thanx for your input, rich

Yes - a vehicle equipped with the base axle ratio would not show the ratio on the SPID.

A vehicle equipped with an optional ratio would have it listed.

K