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Old 05-06-2014, 01:30 AM   #1
brisonac
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Trans/ Gear ratio question

Right now I have a 402 (350-400 HP est) in my 72 with a TH350. Im not sure of the gear ratio, cant find out what it is for sure. The top speed right now is only like 65-70 at high rpm. Im looking to get an OD trans and better gears. What are your suggestions? Thanks guys!
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Old 05-06-2014, 01:36 AM   #2
Sklptrljay
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Re: Trans/ Gear ratio question

You probably have 4:11's. Check your SPID in the glove door. You can do a simple check by counting tire revolutions and driveshaft revolutions. Or obviously remove the cover and count the teeth on your gears.
A 4 speed with od will definitely help. Most guys seem to prefer 3:73's with a 700r4 od tranny.
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Old 05-06-2014, 01:51 AM   #3
SS Tim
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Re: Trans/ Gear ratio question

Stock ratios are not indicated on the SPID.
If you know what the original powertrain was (it can be read or deduced from the SPID) then just look it up on the powertrain charts I posted. Since the only stock thing we know about your truck is that its a 72, the rest is up to you.

* VIN/Model Decoders
* Power Team Charts (engine/transmission/gear ratio)
* Post Your Pickup SPID Blazer SPID Suburban/Panel SPID
* RTFM
... Read The Factory Manuals... download 'em here
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Old 05-06-2014, 02:03 AM   #4
BigMike
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Re: Trans/ Gear ratio question

Quote:
Originally Posted by SS Tim View Post
Stock ratios are not indicated on the SPID.
My 69 does - Rear Axle 373 Ratio

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Old 05-06-2014, 02:13 AM   #5
SS Tim
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Re: Trans/ Gear ratio question

If you are going to quote me then please check your facts first.
Your truck stock would have been built with 3.07 gears, but since it was ordered with the optional 3.73 gears (RPO H05) they are listed on the SPID.
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Old 05-06-2014, 04:06 AM   #6
BigMike
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Re: Trans/ Gear ratio question

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