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New gears really going to help with mpg?

you got me thinking though, maybe the gearing change will help with the shift points as the tail shaft will be spinning faster with the 3.55's?
 
Yes, as relates to car speed. The gears will have no effect on the shift point in relation to engine RPM. The AOD has no idea what the vehicle speed is; it can only relate engine RPM and throttle position to output shaft speed.

-Rory
 
so since the tail shaft rpm will be faster with the lower gear for the same car speed, the shift points will be different for the the car speed?
 
Perhaps a contrived/simplified example will help...

Suppose you have a car with an AOD that behaves as follows:

At 4800 RPM it shifts and the 2-3 shift is at 40 MPH with 3.0 rear gears...

You could change the governor weight to increase or decrease the shift point as it relates to engine RPM

If you change it to shift at 3500 RPM the 2-3 shift will happen at a lower speed, say 35 MPH

If you change it to shift at 5500 RPM the 2-3 shift will happen at a higher speed, say 45 MPH


Now instead of changing the governor weight, you change the rear end gears...

It you change to 2.5 rear gears it will still shift at 4800 RPM, but the 2-3 shift will be at a higher speed, say 45 MPH

If you change to 3.5 rear gears it will still shift at 4800 RPM, but the 2-3 shift will be at a lower speed, say 35 MPH

Note that all numbers above are made up, it is not meant to imply that changing the governor weights maps directly to rear end gear ratio changes, and there are other factors that affect shift points that are being glossed over in the interest of clarity/simplicity.

Hope this helps...
-Rory
 
"2ndgen" said:
Perhaps a contrived/simplified example will help...

Suppose you have a car with an AOD that behaves as follows:

At 4800 RPM it shifts and the 2-3 shift is at 40 MPH with 3.0 rear gears...

You could change the governor weight to increase or decrease the shift point as it relates to engine RPM

If you change it to shift at 3500 RPM the 2-3 shift will happen at a lower speed, say 35 MPH

If you change it to shift at 5500 RPM the 2-3 shift will happen at a higher speed, say 45 MPH


Now instead of changing the governor weight, you change the rear end gears...

It you change to 2.5 rear gears it will still shift at 4800 RPM, but the 2-3 shift will be at a higher speed, say 45 MPH

If you change to 3.5 rear gears it will still shift at 4800 RPM, but the 2-3 shift will be at a lower speed, say 35 MPH

Note that all numbers above are made up, it is not meant to imply that changing the governor weights maps directly to rear end gear ratio changes, and there are other factors that affect shift points that are being glossed over in the interest of clarity/simplicity.

Hope this helps...
-Rory
Click to expand...
Or you could just put a T5 in it!! lololol :nk
 
I got the gears in today. Damn, I am getting too freakin' old at 54 to be shuffling gears...lol. I'll put the drive shaft in tomorrow and giver 'er a try. :scar
 
Drive them easy until they get broken in or you will for sure Brake then...in....

How about pics?

Mel
 
Mel, these were used gears I got from a nice fellow on here. What do you want pics of? Meanwhile I have a nice used rebuilt recently set of 2.80 pumpkin gears to sell....lol. I love the 3.55's but I will have to change the speedo gear as the speedometer is way off now...lol.
 
"gwstang" said:
Mel, these were used gears I got from a nice fellow on here. What do you want pics of? Meanwhile I have a nice used rebuilt recently set of 2.80 pumpkin gears to sell....lol. I love the 3.55's but I will have to change the speedo gear as the speedometer is way off now...lol.
Click to expand...

Hehehehe, I just wanted to see a pic of you struggling to put in the new set. I am so sadistic! Hehehehehe...

Mel
 
Hey, everything sounded just fine and no leaks anywhere so I am glad about that. As far as I can tell, the gears are smooth as silk! :)
 
Oh you are very bad. I am going to give Mr. Midlife your address..lol he he he . :nk
I've actually been to his house in Panama city Fla. He keeps the " curse" in the garagemahol in a genie bottle on the shelf just waiting for an opportunity to use it. :weas
 
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