udidca302 2 Posted June 16, 2016 I am doing a complete rebuild on my drive line and when it comes to diff ratio I have no idea what to go with. At the moment it is a 3.25:1 ratio ford 9 inch lsd. I would like the car to haul and not lag when it is given the boot. Any ideas of what ratios to look at. Engine is a 351 Cleveland with about 350hp, c4 gear box shift kit and 2500 stall. Tyre size at the moment is 255/50r15 looking at going 245/40r18 Share this post Link to post Share on other sites
Thom 6,639 Posted June 16, 2016 What do you want to do with the car? Occasional street/strip, cruiser or a long haul driver personally I'd stick with the 3.25's as it would get you above you stall speed at 100ks and the are a good compromise between highway gears and low down take off Share this post Link to post Share on other sites
udidca302 2 Posted June 16, 2016 Mostly street with the occasional strip. Share this post Link to post Share on other sites
Thom 6,639 Posted June 16, 2016 I'd still stick with the 3.25's 1 gerg reacted to this Share this post Link to post Share on other sites
wagoon 2,429 Posted June 16, 2016 Yeah Im with Thom, you will want to use the torque of the engine which happens better with a slightly taller gear. Shorter gears are for higher horsepower cars that rev higher. If you did very little highway driving you could change to a 3.45 ratio as that will help with moving the car better. 1 Thom reacted to this Share this post Link to post Share on other sites
udidca302 2 Posted June 17, 2016 My mistake people I did the ratio test today looks like it's a 2.85:1 ratio. Kind of a bit pissed about that because it was meant to be a 3.25:1 anyway would it be better to change the ratio of t to a 3.251 or would the 2.85:1 suit Share this post Link to post Share on other sites
Jestr75 41 Posted June 17, 2016 Probably better to take the cover off the diff and see what is stamped on the gears so you know for sure. 1 SirkWhyXF reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted June 19, 2016 Probably better to take the cover off the diff and see what is stamped on the gears so you know for sure. 9-inch is a drop-out centre, no cover to unbolt at the back. That means axles, brakes, tail shaft all need to come out. I thought the closest ratio was 2.75, am I right? I was under the assumption that all factory ratios were non-hunting type vs Borg Warner type that were hunting Share this post Link to post Share on other sites
Jestr75 41 Posted June 19, 2016 9-inch is a drop-out centre, no cover to unbolt at the back. That means axles, brakes, tail shaft all need to come out. I thought the closest ratio was 2.75, am I right? I was under the assumption that all factory ratios were non-hunting type vs Borg Warner type that were hunting Thanks Gerg! I was thinking Borg Warner diff, my mistake. Share this post Link to post Share on other sites
gregaust 315 Posted June 19, 2016 I like 3.5's with a tall tyre . Good all round ratio IMO 2 MNTL.XD and XF347 reacted to this Share this post Link to post Share on other sites