*This is a poll that doesn't really need a question,* but more of a posted response. So there is no question to click an answer. 2 part question. 1st part fact, 2nd part opinion/analysis... A: What is your final drive ratio? Formula: Tranny 1st gear ratio x rear differential ratio = final drive ratio in 1st gear. B: How does your car act in 1st gear? Example:Do you wish it accellerated harder? (too little gear) or Does it rev slowly and go through gears before it seems to really 'get moving'? (too much gear) or Your engine is high rpm, revs fast, but you need lower gears because it bogs a bit? Just provoking some thought on how your engine is built and the resulting interaction with your transmission/differential gearing... Maybe the discussion will cause the whole relationship of the parts to each other, 'click' for some of the members that are still learning. Or maybe it will help someone on the fence decide just what gear he might end using, and get them off the proverbial fence. Use examples of any gear/engine combo you may have used and have firm opinions on. Don't use examples that you didn't use in your own car... Like my cousin's uncle's father-in-law had 3.55s... Stick to classic Ford cars, differentials, and common tranny swaps into these cars. If not discussing a Maverick, remember that they are very light compared to most other classic Fords. So a certain gear ratio will act differently between a heavy car/truck vs Maverick. Not to mention taller tires on big cars/trucks skewing effects. Make it a learning experience.
I'll start... 72 Mav, relatively high strung 306... 1500-5500 rpm. C4 with approx 2.40 1st gear ratio and 4.11 gears. 9.86 final drive in 1st gear. This combo made for a fast accellerating 306 in the light car. Traction was borderline at best on radials. The cam was what I would call a 'large RV' cam, with single plane intake... No stall converter. 4.11s behind the C4 were extremely fun in 1st gear. I know it isn't germained to the discussion, but the 4.11s REALLY sucked in 3rd gear, going down any sort of highway. Summary: 9.86:1 first gear = FUN with a mild to moderate SBF/light car that can make power to ~5500 rpm.
Remember that if we focus almost totally on 1st gear, the tranny type is nearly irrelavent. The accelleration characteristics are made/broken in 1st gear, so that ratio can be compared 'apples to apples' between any 2 trannys. The rest is only a sidenote to this discussion.
A: Not the Mav, but my Capri ran a 2.95 first T5z and a 4.10 8.8" rear, so 12.1:1? Anyhow, the Capri weighs about what the average Mav weighs, so I figure the data is valid. B: I think I had too much gear. First gear in that car was useless with 4.10s and 225-60-15s. No traction. I think less gear would be better, but all I have to compare it to was the stock 2.73s which were way too tall. If the car had traction, I still would not recommend the 4.10s with any engine that wont pull well into the 6k territory. It just runs out of steam too early, and you will be shifting way too often IMO. FWIW, my engine made 233/286 and was done at about 5k.
Big bumper car, high strung 306 (228/235 cam), power band 2500 (barely) to 6500+ rpm. Toploader wide ratio 2.78 first gear. 3.00 rear gear. 8.34 final drive in 1st gear. Geared too high for the engine combo. If I stabbed it straight off the line, the engine rpm was too low to make power, so it bogged. This left me needing to dump the clutch and force wheelspin to get the engine in it's power band. Having a small bumper Mav might have improved things because less weight would have allowed the rpms to rise faster. Also, we are dealing with a non-stroked SBF. So fast revs are more important than using torque that just isn't there. Summary: 8.34 final drive. Probably plenty of gear for an RV cammed engine or lighter car, but with power only beginning to arrive at 2500 rpm, then coming on strong above 3k, it just isn't enough gear. ---------------------------------------------------------- Same car... 4.11 gears. 11.43 final drive 1st gear... What can I say but FUN FUN FUN! Now that the engine stays in it's 3k+ power band, it feels like it actually makes some torque. Wheelspin is dramatic and at will. Slicks would be a must on the occaisional trip to the track. Summary: If you have a final drive in the 11.43 neighborhood, you better be able to rev high and fast. If you can, it's a beautiful thing! ---------------------------------------------------------- Same car, 351c 4v, almost bone stock. Terrible. 11.43 ratio with even a 4v Cleveland that is stock is horrible. The engine revs slower than the gears can be utilized. So you end up going 5 feet, then shifting to 2nd... which is not the focus of the discussion. If you have ever driven a dumptruck or granny geared 4wd, then you know what too much gear feels like in a Maverick. Summary: 11.43 final drive is best left to high strung engines in light cars. -------------------------------------------------------- Same big bumper, 351c 4v, 2.78 1st gear... converted to 2.79 rear. 7.76 final drive. What a difference! It made the stock 351c a pleasure to stab off the line or at a light. It was no dragster, but it drove like what a stock 351c 4v should. Summary: 7.76 final drive. Don't let the 2.79 rear gears fool you. Do the math. First gear's final drive is equivalent to a 3.25 gear behind a C4. Knowing this, you can image how street friendly 7.76 is with a stock engine.
Not sure on the C4 thing. I also had a Mustang II with a C4 and 3.00 rear 9". Whatever final that is. Tranny had a 2800 stall, stock early 302 heads, Comp268 cam, Edelbrock Performer 289, 600 Holley vac sec carb. That car bogged BAD with a 3.00 rear gear and that C4. It was horribly underpowered for that gear ratio and had no acceleration from a dead stop. Once it shifted into second it would get rubber and the car felt pretty quick if you punched it from a 40mph roll. At the same time, it turned higher than I liked on the highway, so it was the worst of both worlds. LOL I have been spoiled with overdrive for sure.
Well it seems it would be a good idea to list the ratios for stock rears. Just so folks can gauge the feel of stock gearing. C4 with 2.79 gears = 6.70 C4 with 3.00 gears = 7.20 3 speed with 2.79 gears = 7.76 3 speed with 3.00 gears = 8.34 Other common combos: C4 and 3.25s = 7.80 C4 and 3.55s = 8.52 C4 and 3.80s = 9.12
How about 3 speed manual with 4.56? That's what my 1900 pound Fiat Spider had with a 302/Edelbrock heads/Hooker Headers/Peformer RPM intake/600 Holley. First gear was a joke. You couldn't even use it creeping along in traffic, because of how bad the car would jerk around no matter how smooth you tried to be on the gas. And of course it would just send the tires up in smoke if you really tried to get on it at all in first. I took off in second 90% of the time. It would eat about anything alive from a 25 mph roll in second, snatch 3rd and just bury the speedometer needle. Bye bye Corvette, Mustang or whatever.
my car 2.95 1st 3.73 rear = 11.00 Tammy's 3.35 1st 3.73 rear = 12.49 (that's why she crashed spinning the rear tires)
Dave your thread is interesting and informative, but you're leaving out a very important factor in the final drive ratio...........the size (diameter) of the rear tires. Going from a 25" tire to a 29" changes the final ratio immensely. Take my Comet with 26" tires (295/50/15) and it's 3.50 ratio rear. The final drive is almost the same ratio as my V8 Ranger's 3.73's with 28" tires (275/60/15). Just food for thought..............
Yeah, I realize. I just thought that the number itself was pretty informative and felt that weight, cam specs, and tire size factors, while all important, would just confuse the issue for folks that are not familiar with the gearing concept. One step at a time!
