Axle ratio help

[84GMCSierra]

Hello everybody. I'm trying to figure out what the gear ratio is on my 84 base model 3/4 ton Sierra is. The SPID says GQ1 Rear Axle - Standard. I tried finding it online and the GQ1 isn't listed. Can someone help me out with this please? Engine is a 350, and the trans is a TH400. I'm hoping they are something for daily driving, and highway use once in awhile.
Thanks

 

[legopnuematic]

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Or pop the rear cover and count the teeth/find the numbers on the ring gear to verify. If you haven't changed the gear oil in your ownership it's probably time to do so anyways. Gear oil is cheap compared to rebuilding a rear axle.

 

[Keith Seymore]

Well done, Lego.

Just to flesh it out a bit more: I see C20903 W LT9 with the three speed auto (non overdrive = MX1) so I'd call it 4.10:1.

K

 

[Keith Seymore]

Hello everybody. I'm trying to figure out what the gear ratio is on my 84 base model 3/4 ton Sierra is. The SPID says GQ1 Rear Axle - Standard. I tried finding it online and the GQ1 isn't listed. Can someone help me out with this please? Engine is a 350, and the trans is a TH400. I'm hoping they are something for daily driving, and highway use once in awhile.
Thanks

Correct. For base axle GQ1 the SPID shows GQ1 but doesn't specify the numerical ratio, because it varies (as shown on the Powertrain Chart).

For an optional ratio: The SPID will show the RPO and call it out by name (ie, GU6 = 3.42, GT4 = 3.73, GT5 = 4.10 or whatever).

K

 

[84GMCSierra]

Correct. For base axle GQ1 the SPID shows GQ1 but doesn't specify the numerical ratio, because it varies (as shown on the Powertrain Chart).

For an optional ratio: The SPID will show the RPO and call it out by name (ie, GU6 = 3.42, GT4 = 3.73, GT5 = 4.10 or whatever).

K

So I need to pull the cover and count teeth to find out what it is?

 

[75gmck25]

Sine you apparently have a standard axle, without GovLock or other limited slip, you can determine ratios by counting wheel revolutions and driveshaft revolutions.

This one site with an explanation of how to do it. https://www.moderndriveline.com/how-to-determine-your-rear-axle-ratio/

 

[mtbadbob]

Put it on a lift, turn your rear wheel one revolution, and count how many times the drive shaft rotates in that same revolution.

 

[Ricko1966]

Put it on a lift, turn your rear wheel one revolution, and count how many times the drive shaft rotates in that same revolution.

This won't work, if it's open diff,you can push the car on the ground,1 revolution stop every 1/4 turn check and mark your drive shaft. Or jack up 1 wheel and turn it through 2 revolutions and count your driveshaft turns. Nevermind it's 4.10,look at the power train chart @legopnuematic put up for you. All 350s with the mx1 transmission and gq1 axle are 4.10