transmission options for mavericks

I run 255/60/15 Cooper Cobra tires on the back of my Grabber and Comet, but they are 27" tall, not 25.5" tall.

 

Maybe I oughta put some more air in mine?? I expected them to be taller but 25.5 is what they measured...

 

Wow!

What brand tire?

 

I checked out the Gear Vendor website to compare some Ford 8" gears to the what the final gear ratio would be through the Gear Vendor overdrive unit.

A 4.1 becomes 3.2
A 3.9 becomes 3.04
A 3.73 becomes 2.91
A 3.55 becomes 2.77
A 3.23 becomes 2.52

Basically the Gear Vendor overdrive unit multiplies the existing rear end ratio by 0.78 to end up with a lower ratio.

A lot of folks like a 3.55 and some who like racing go up to a 4.1 and beyond. If you like your present cruising RPM, you could go to a 3.73 rear end and achieve the same result as a 2.91. If you want to save some money on gas at cruising speed, a 3.55 and a resulting ratio of 2.77 probably makes a lot of sense. The Gear Vendor unit for a Ford C4 shows up as a $2800 on their website. Maybe there are better deals out there.

I'll open this up to the folks on the Forum for other opinions. Thanks.

M.D.

 

I am going to have to get it in my head that the final drive is a COMBINATION if the transmission in overdrive and the rear axle ratio.
This car is unmolested and just as it came from the factory. When the trans shifts into overdrive at about 45 mph the engine will need to be turning about 2000 rpms. This car has P205/70/14 Michelin Defenders on stock rims. The speedometer is about 3 miles slow, compared to my GPS. I presume I will need to install a 3:50 gear in combination with the 4r70w trans. and I presume I can get one.
I believe the Crown Vic has a 4R75W and a 3:27 RAR. At 70MPH the car is turning about 2200 rpms. That is what I want my Maverick to do. I'd bet it will get good fuel mileage. Thanks for the information and the reply. Craig.

 

I am going to check this out. This is some interesting information. Thanks for your reply. Craig.

 

with my AOD...275/60/15s...3:55 gear it got 22 MPG on a 3300 mile road trip. maybe it was just idleing at 80 MPH at 1800 RPM...
...

 

I guess I don't get the RPM hang up, I have had plenty of cars in the past that cruised just fine at lower RPM. One of my Torino's would cruise down the highway in fourth under 2000 RPM with no issue, they were built to do it all day, every day.

 

No, I don't get it. I read in the transmission section of this website that a carbruetor doesn't get out of the idle circuit until at least 1800 rpm. It goes on to explain that the engine needs to turn faster than 1800 rpm for that reason. Apparently, I don't get it because I thought a person would want to gear lower so the engine wouldn't be lugging.

So, I am going to ask, gentlemen, what rpm does my car need to turn when it is in overdrive? What rear axle ratio do I need to select? I know it depends on some factors, but, humor me; throw something like 3:55 out there. Thanks for your reply. Craig.

 

This might be fun. OK, set a couple of parameters. What speed do you want to cruise at? As far as the RPM, I recommend low 2,000's. In my opinion, 2800 rpm is too buzzy. How about 2200 RPM at 65 mph. Any other suggestions? Also, I need an average tire height ie 25" to 27". (26" might be a good average). I'll calculate a rear end ratio for both a 1:1 tranny third gear and a 0.78 over drive. Just give me your ideas. Thanks.

M.D.

 

How about 2200 rpm at 70 mph? A p205/70R14 Michelin defender measures about 25". Work your magic. Craig.

 

OK, without taking into account any slippage of the torque converter, I'm thinking you can go 70 MPH at 2200 RPM if you put in a 3.0 rear end (which coincidently comes with the 302 in Mavericks), and you would need a 0.78 overdrive (which is what the Gear Vendor ratio is for use with a C-4).

If someone has some info that would blow this out the door I will look at it and check my calcs for errors.)

However, if you want a sportier rear gear such as a 3.55 you could cruise at 70 MPH with an overdrive if you were OK with 2600 RPM. Just to check, for those of you running a 3.0 rear end with no overdrive and a 25 inch tire, what RPM do you do you see at 70 MPH? (not that any of you speed! LOL) My calcs would say 2800 RPM. How far am I off?



All this was with a 25 inch tire. Thanks.

M.D.

 

Well crap! I've wasted your time! I didn't know you could just bolt this gear vendor thingy on. (Do you think that is why someone mentioned this sometime back?) That unit is $2800.00? I think I am going to look at that.

I don't want a sporty gear; what I want is for my Maverick to do the same thing my Grand Marquis, and Crown Vic do; just shift into overdrive, quiet that engine down and then I can engage the cruise control. (Yes, I have an aftermarket unit on my Maverick.) Thanks for your time, Craig.

 

You can run a little less rear with the gear vendors unit as it's ratio is .78 vs .70 for a 4R70W... Also when in OD, the 4R70W converter locks(at least in factory trim) so there is no converter slippage, which is generally around 200 RPM... Thirdly the 4R70W has better ratios than the earlier transmissions, first is 2.84 vs 2.40 for a C4/AOD/AODE... Second is 1.55 vs 1.47 in the other transmissions...

 

Around here 70 isn't speeding and in Idaho it just makes other drivers angry with you for holding up traffic!