Best Gears for C4 Tranny

Madlx5.0

New Member
Sep 9, 2006
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Need advice on which gears to use with C4 tranny in my 89 Mustang 5.0 I was thinking about 3.55 but not sure if rpm's will be to high while cruising. This car is just a street car and not a daily driver, mostly driven on weekends.
 
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With taller rear tires, and 3.55's, your will be cruising at around 3,000 rpm at 60-65 mph. Had them in my '65, and would not have gone any taller for the amount of highway driving I did with it.
 
really depends...
are you going to be taking it to the track? if so 1/8th or 1/4?

what kind of tires will you be running? 26 or 28" slicks or regular street tires on 15/16/17/18" rims?

One thing to remember is c4 has a crappier 1st gear than most other trannies so it can leave it sluggish out of the hole without a low gear in the rear. But on the other hand if you have a low gear like a 4:10 you can sufer from highway rpms killing your gas mileage. Also when you put a taller tire on it will lower your rpms as compared to a smaller tire at the same speeds.

My coupe will have a 4:10 rear gear since it will be an 1/8th mile car with mostly around town playing. This will help get it out of the hole and down the track. I will most likely have 26 or 28" tires to.
 
Going from 3.08 to 3.55 gears

Thanks guys !! I currently have 3.08 gears and was wanting to try another gear to get me out the of the hole quicker from stop light to stop light. I currently have 225/50/R16 tires with stock pony wheels. Cruising at 60-65 mph at 3000rpm doesn't sound to bad. I may go ahead and try 3.55 gears. Will the 16in tires that I currently have be tall enough for 3.55 gears.
 
For driving much at all, the 355's will get old. I have 273's in my 79 and it is very busy to drive on the interstate at 70 or more, to the extent that I avoid it. I do drive it 35 miles each way to work on the interstate once a month, but it's not really fun.

I have 4.10's in the 82, and a couple miles at 70 is all I can take.

The 82 has 275-50 Drag Radials and is just maxed out at 105 mph/6000 rpm at the finish line of a 1/4 mile track.

I have a 4.56 that's a bit better on the launch, but its only good for 1/8 mile tracks.

I calculated this a long time ago, and kept the 4.10 so I can run 1/4 mile tracks as well as eighth. The 4.56, eight miles, and nitrous are fun.