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**First c10** · 03-13-2017, 02:56 PM

Not sure the above is accurate.
the stock trucks with the 6L transmissions either have a 3.07/3.08 or the option of a 3.42

I installed a 5.3/6L80E in my sons truck with the stock 3.08...I had to put a posi in it as it would light the one legger up!

Since the the trans has 6 gears 3.08 gears are like 4.11 in first gear.
If you were putting a 4L trans I agree you will need 3.73 or 4.11. but the 6L? I would wait till the truck is running you will be amazed as my sons truck is a rocket.

03-13-2017, 02:56 PM	#7
First c10 Registered User Join Date: Dec 2012 Location: Los Banos CA Posts: 2,705	Re: 4.8L/6L90E swap??? Not sure the above is accurate. the stock trucks with the 6L transmissions either have a 3.07/3.08 or the option of a 3.42 I installed a 5.3/6L80E in my sons truck with the stock 3.08...I had to put a posi in it as it would light the one legger up! Since the the trans has 6 gears 3.08 gears are like 4.11 in first gear. If you were putting a 4L trans I agree you will need 3.73 or 4.11. but the 6L? I would wait till the truck is running you will be amazed as my sons truck is a rocket. __________________ 1956 Chevy Bel Air 2 door 1956 Chevy 210 4 Door 1970 K20 LWB project the Hulk build w/Supercharged 4.8L-ly2/4L60E HULK BUILD 1970 C10 Yellow/White Deluxe LWB w/ 5.3L-LC9/6L80E 1968 K10 LWB Dark green my son calls it "THE HULK Jr"HULK JR SOLD GO GO!!!