Hola chicos. Tengo un cupé 32 con motor de válvulas planas 49. Isky 88, Stompberg Tripower 97, Pertronix, culatas Navarro y pistones Ross. Transmisión Volvo 240 de 5 velocidades. Quiero una caja de cambios diferencial, actualmente con una relación de 3,55:1. Parece que va en marchas cortas. Quiero cambiarla a una de 3.07:1. ¿Sería una buena caja de cambios? Gracias.
Do you have a tachometer, so you see engine Revs Per Minute (RPM)? Do you know what the ratio of 5th gear in the transmission is? How fast do you want to drive the car?
I am going to make a couple of assumptions, so bear with me. Assumption #1, 5th gear is overdrive with a 0.70:1 gear ratio (tall, but that is what seems to be typical for a 240 Volvo). Assumption #2, you are using a 31 inch (78.75 cm) diameter rear tire. Those two assumptions result in the vehicle doing 72 mph (116 km/hr) at 2000 RPM in 5th gear. A bit too steep of gearing for a flathead, even a well built one. If you switch to a 5.07:1 rear axle, the car would now be doing only 50 mph (80 km/hr) at 2000 RPM. Probably a bit low as I would target 2000 RPM to be around 62 mph (100 km/hr), but that is my preference. A set of 5.07 gears would definitely wake the car up in the stop light to stop light arena. Given these assumptions, I would probably split the baby and shoot for a 4.11:1 rear gear set. If either of my assumptions are incorrect, and you have a different 5th gear ratio or a smaller tire, the math will change. That said, I am not sure what your parts options are in Spain, but you can get a 9 inch Ford Rear Axle in just about any ratio imaginable between 2.5 and 7. Get ahold of Quick Performance, have them build one to your specs and send it over the pond.
Looks like Volvo 240's with a 5-speed have either .77, .79, or .82:1 fifth gear. You haven't told us your tire size or what you're trying to do, but with the relatively short fifth gear I can't imagine a situation where that 5.07:1 would make any sense.
Relación de transmisión 1º 4.03:1 2º 2.16:1 3º 1.37:1 4º 1.00:1 5º 0,83:1 rueda: 31 pulgadas (78,75 cm) de diámetro 68 milles is 2.200 RPM approximate Gracias
2,200 seems fine, what's the issue you're trying to resolve? If you want it to run higher RPM, shift down. 68 MPH with the 5.07 would be 3,100 RPM. For an overdrive for North American use, that's not a good gear choice. I don't know what your roads or use is like.
Parts of spain are quite mountainous so maybe that will work. @Masot what rear end are you running? Banjos are limited to 4.11 on the upper end for any readily available gears.
sorry, sorry,sorry... new is 3.07:1 not 5.07:1 Now, having a 3:55 banjo is very noisy. I want to upgrade to a Jeep Cherokee XJ and suspension. It's better for traveling. My question is, should I keep the same 3:55:1 setup or change to a 3:07:1?
@Masot is it a Volvo M46 or M47 transmission. At 3000 rpm it would be shifting at 19 mph with the 3.55 BUT it is 22 mph with a 3.08 Hardly fixes the problem of the huge 1-2 ratio drop of the Volvo transmission. The Volvo M46 box has these ratios 1st = 3.71:1 or 4.03:1 2nd = 2.16:1 3rd = 1.37:1 4th = 1.00:1 Overdrive - 0.79:1 The Turbo Volvo 240's had the lower first. The Volvo M47 box has these ratios 1st = 4.03:1 2nd = 2.16:1 3rd = 1.37:1 4th = 1.00:1 Overdrive = 0.82:1 If your transmission is a M46 , hunt down a Non-Turbo [3.71:1 1st] transmission. This has the same effect as a 3.08 rear in first, but all the other gears overall ratio remains the same. Both transmissions can get destroyed with 240 ft/lbs + Whack a T56 into it [and have the best of everything] These can be converted to "Front Shift position"
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