Mavs running!!!

Thanks to everyone here my Mav is running like a beast. The only issue I have is when im doing 75-80mph the tach is around 3500-4000rpms and not sure what I can do to make it a lot less. Im staying at 70mph since thats the speed limit and my engine can only handle 4500-5000rpms Please let me know what I can change to correct this beside the transmission and torque convertor I will cry if I have to get back under there and remove it again.

 

If you're running the c-4 and stock rear gears (probably 3.00:1 ratio) then the rpm's sound right at that mph.
The only solution to the rpm issue, is to put a higher ratio ring and pinion in the rear end, or install an AOD or five speed manual transmission.
Check the tag on the rear end and you should see a 3.00 or 2.79.
If you do a lot of highway cruising and want your rpms lower, then you will have to drop the number lower.
Remember, the lower the number the higher the ratio and the higher the number the lower the ratio.
The lower the number, the less your rpm's will be at highway speeds, but your take off power will suffer, due to the high ratio gear set. If you have the 3.00 gear set in your rear end, then the 2.79 would probably suit your needs.
If you really want to drop the rpm's, then go with a ratio in the 2.50 range. That should knock your rpm's down to the 2500-2800 rainge at 80 mph.

 

I will look into swapping the gears in the rearend. Do I have to buy new gears or are there vehicles I can get that part out of that fits the maverick? Thanks for your help!:Handshake

 

I would buy new gears, unless you are going to swap out a whole 8 inch pumpkin. Even then, the gears could have excessive wear. You just need to be careful in inspection of the used gears. New is the direction that I would go.

 

If you have stock wheels and tires you could benefit quite a bit from taller tires.

 

I don't think your speedometer gear matches your tire size. Do you remember what color the speedometer gear was? Get a tape measure and measure the rear tire height. A taller rear tire is 4 or 5 times cheaper than swapping gears.

 

Taller tires will drop the RPMs. But it's a trade off. The taller the tire, the higher the center of gravity, the worse your car will handle.

If you have your tire size and gear ratio you can use this table to find a tire size that will put the rpm where you want it. I'm not sure what the final drive ratio is with an auto, I think I would use 1.05:1 for the purpose of calculating rpm. I forget how much to add to compensate for slippage. I am guessing 5%. If that is incorrect someone will surely correct me.

http://www.car-videos.net/tools/speedrpm.asp

 

I guess, it all depends on how much you want your rpm's to drop.
A tire tall enough to make your car look rediculous, will drop your rpm's by few hundred at best. If you want a serious reduction in rpm's, the gear change is the way to go.

 

The tach is set for a v8.

 

I have stock rims and tires on it now. The gear color was orange or red. I guess it would be best to change out the gear. I will look and see what I can find for an 8 inch rear. Thanks for all your help so far!

 

I agree with rear gear swap. 2.79 should knock your rpm's down to a reasonable speed.

 

Ok I think this whole thread is a bit unreasonable. Lets break it down with the calculator:

You have stock size tires (lets assume 185/70-R14) and We will also assume the rear is a stock 3.00:1 I set the increment to 50 rpm and see what we come up with. Looks just like what you said...
185/70-R14_____ 3.00:1 gears_____ speed= 80.5 MPH _____RPM=3650

Lets try a bigger tire:
255/60-R15_____ 3.00:1 gears_____ Speed= 80.1 MPH_____ RPM=3250

OK. Lets swap for the 2.79 rear with stock tires:
185/70-R14_____ 2.79:1 gears_____ speed= 80.6 MPH_____ RPM=3400

Now lets go nuts. Big tire and 2.79 gear
255/60-R15_____ 2.79:1 gears_____ Speed= 80.8 MPH_____ RPM=3050

Now I am thinking this is still WAY too high for you. My question is WHY? If you could gear this car to cruise at 75 - 80mph at 2500RPM or less, It will be an absolute dog off the line! It will take forever to get into an RPM with usable torque. No, I am gonna have to say if you want to drive that fast at a low RPM, you are gonna need an overdrive transmission. PERIOD. A newer car with airbags, anti-lock brakes, modern crumple zones, safety cage, modern handling and braking would be far better suited for what you are trying to do. Sorry to be such a party pooper.

 

Shane,

I have a 2.79 pumpkin. I'll trade you for the 3.00 if you come pull it. We can do the swap at my house on the lift if you want.

Rick

 

Yes! Maybe keep the small tire and gear and add a gearvendors unit. Just a thought.

 

Cheaper to add a built AOD...

http://www.lentechautomatics.com/aodpricing.html

http://www.gearvendors.com/hrford3s.html