The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

tucsonjwt · 07-24-2013, 04:56 PM

I have a 4:10 rear axle ratio. Effectively, you are reducing the final drive ratio by 20% (at least that is the way I interpret it) through each gear. So, I guess my 4:10 ratio is really 3.28 when engaging the GV. Practically, I can only use the GV in 3rd and 4th gear, so I guess you could say the GV gives me a 6 speed transmission.

Coupling a granny 4 speed with a 4:10 rear axle ratio is a real mpg killer. The previous owner had a truck camper on my truck (camper special), so that is probably why he had the GV installed. I don't have a tachometer but I can sense the RPMs drop with the GV engaged.

On automatic transmissions, you can select the mph where you want the GV to engage. My truck has a 20/40 rocker switch on the dash which I think is for that purpose, but since I have a manual transmission the local GV mechanic says it is just an on/off switch in my truck.

07-24-2013, 04:56 PM	#9
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,198	Re: Overdrive for a 454? I have a 4:10 rear axle ratio. Effectively, you are reducing the final drive ratio by 20% (at least that is the way I interpret it) through each gear. So, I guess my 4:10 ratio is really 3.28 when engaging the GV. Practically, I can only use the GV in 3rd and 4th gear, so I guess you could say the GV gives me a 6 speed transmission. Coupling a granny 4 speed with a 4:10 rear axle ratio is a real mpg killer. The previous owner had a truck camper on my truck (camper special), so that is probably why he had the GV installed. I don't have a tachometer but I can sense the RPMs drop with the GV engaged. On automatic transmissions, you can select the mph where you want the GV to engage. My truck has a 20/40 rocker switch on the dash which I think is for that purpose, but since I have a manual transmission the local GV mechanic says it is just an on/off switch in my truck.