Cruising Gear?

[Agent M79]

So you have tallish gears... 4.10's, 4.30's, 4.56' with the intent to get more punch off the line and a satisfactory progression from 1-2 and 2-3.

Bet then.... you are an over-the-road traveller and have need to travel interstates for extended periods of time...

...could 4th (overdrive, right?) gear be changed out for a gear that allows the MM to cruise at a low rpm range to help with overall mileage?

I am betting its: A) doesn't work that way, Dave... or B) Sure you can, but it is heinously expensive... or 3) Are you off your meds, Dave?

[BillyGman]

Dave, are you off your meds? okay, just kidding.........

here's some help for you(sorry, not more meds)......use the following link to help you figure out what you'll be reving at at 70 MPH or any other MPH for any gear ratio that you want to punch in. keep in mind that overdrive for our cars(or what you're calling fourth gear) is a .71 ratio, and third gear is 1.00 ratio and the tire height of our stock tires is about 28.0".

www.richmondgear.com/streetcalculators.html


with 4.56 gears my car revs at 2750 RPM's at 70 MPH in overdrive. Which I think isn't bad at all. I forget where it was reving when I had the 4.10's but you can now use the link to figure that out for yourself.

but whatever you do, if you do decide on a gear change, do NOT use Richmond gears if you plan on a 4.10, 4.30, or 4.56 gear ratio because any ratio that is lower (numerically higher) than 3.70 w/the Richmond gears makes a lot of whining noise even when the gears are installed correctly. Ford racing gears will not do that as long as they're installed correct.

I was in a car once that had Richmond 4.11 gears (it was a Chevelle) and it sounded like I was riding in a dump truck or something similar because of the way the rear end was whining!!!!! The Richmond tech department confirmed that for me. it's because of the way the teeth on their gears are cut. The noise they make is annoying. NOT what you want in a street car.

[Ross]

Just so everyone will know, Dave really is off his meds... :eek:

[BillyGman]

Lol........

[TripleTransAm]

It IS possible to change out the overdrive for another ratio. However, you gotta understand how an automatic transmission is designed. It isn't like a manual transmission, where the gear ratio is a result of ratio in the number of teeth between two gears meshing. Auto trannies use planetary gear sets... you have a sun gear (a shaft with teeth around it) with small planetary gears 'walking' around the center gear, with their axes held by a carrier, and then an outer 'ring' gear... a sort of drum with teeth on the inside, also meshing with the planetaries.

The auto tranny gear ratios are obtained by a selection of which element to hold still (using band clutches) and which elements to grab the drive torque off of, using the regular small multi-plate clutches. With just two of these planetary sets of gears, you can get your traditional 1-2-3 gear ratios...

My point... to get a different gear ratio in overdrive, you need to totally reengineer at least an entire planetary gear set. It IS possible... there are replacement gear ratios available for racing purposes for the GM Hydramatic trannies (the older 3 speed units) but I doubt anyone has gone to the trouble of redesigning a set for the 4R70W.

It's NOT just a matter of popping off one gear pair and replacing with another...

[Agent M79]

Thanks guys. GoINg baCK oN MY spECIaL happY PiLLs noW.

[crowdog]

GEAR VENDORS, givem a call if 8 forward gears would do the trick.:rolleyes:
So you have tallish gears... 4.10's, 4.30's, 4.56' with the intent to get more punch off the line and a satisfactory progression from 1-2 and 2-3.

Bet then.... you are an over-the-road traveller and have need to travel interstates for extended periods of time...

...could 4th (overdrive, right?) gear be changed out for a gear that allows the MM to cruise at a low rpm range to help with overall mileage?

I am betting its: A) doesn't work that way, Dave... or B) Sure you can, but it is heinously expensive... or 3) Are you off your meds, Dave?