hey guys, i am building a 69 skylark 455 with about 500hp, mainly street and want to run a 200r4 what rearend gears are you all runnning? the .7 overdrive will help alot so i am wondering how deep a gear i should go? i believe 4.30 rear gear =3.08 in overdrive but would the 4.3 be to much for the first three gears? any and all input is apppreciated
I've got 4.10's in mine. The 2004R has a 67% overdrive, it's the 700R4 that has 70%. With a 4.10 rear gear your final drive ratio is 2.75. I started out with 3.73's and at 55mph it ran around 1,600rpm or so. What I didn't like about them is that 1,600 is just a bit below the power band and it tended to lug and buck when scaling long hills if I left it in OD/lockup. With the 4.10's it doesn't do that. I have BFG 275/60-15 tires in the rear and it now cruises at 2,000rpm@55mph and around 2,450@70mph. Since the 2004R has a 2.75 1st gear, I think anything steeper than a 4.10 would give you too much reduction in 1st. A 700R4 would be even worse because it sports a 3.06 1st. An interesting side note is that I run 1/8 mile with the car and my times didn't change one bit when I went from 3.73 to 4.10. Same 60ft, same et, same mph. I have no idea why but it likely has to do with the fact that I now use 3 gears instead of 2 in the 1/8. All I can say for sure is that it hits the tires harder with the 4.10's. I used to be able to hook occasionally with street tires on the 3.73's. I can no longer do that with the 4.10's so I switched to drag radials.
thanks for the input guys, sorry about the ..67/.7 mix up, the suspension should hold the power i am going with dick miller adj uppers and lowers and sway bar, just trying to find the best of both worlds, thanks again
Doug - what size tires are you running? What rpms are you seeing at 60 MPH? I'm looking to go with the 200R4 and am very interested in this discussion! - Bill
I am running 3.55 gears with the 200-4R and 295/50-15s. At 2000 rpms I am going 68 mph. I get around 15 mpg which is a lot better than I expected. Bob H.
I have a tire size/rear axle ratio/ rpm/mph/ transmission calculator so if anyone wants to know mph / 1000 rpm, r/a ratio to give a certain speed at X rpm, etc. for any combo just post the info & I can calculate it for you.
2:75/60/15 Nitto drag radials. I think they are 28" tall. The 3:73's work very well with this combination. With a shorter tire I would go to 3:55's like I have on my GN (3:55 are stock on GN's) I can see no reason to run gears like a 4:10 with a 455/200r4 combination. The first gear is already lower than a TH400, most 455's have lots of low end torque to work with and we do not want to rev over 6000 rpms.
3.73 gears with P255/60R15s and a 350 with a Comp268 cam that likes to cruise at 2200-2500 RPM. Comfortable cruising at hiway speed 70-75 mph. With 3.42s in my combo I had to be going 80-83mph to have the motor rev where it liked at hiway cruise. Also the OD was no good going up long slow inclines with this gearset. my $.02
Not that it will help out much since it's not a big block, but I'll throw in my tid bit. My car came stock with a 200-4r mated to an olds 307 running 215/75r15 (27.7" tall) tires. The original gearing is sub 3 (either 2.7 or 2.9) and the car is a total slug off the line. The rpms are nice and low while cruising which makes for a nice comfortable ride on the highway, but passing power is non-existant. With that in mind I'd say pick a gearset at least 3.23 just so the car has a chance to move out of it's own way. I'm planning on running either 3.23 or 3.42 just to keep the rpms low and the mileage acceptible when I do my 455 swap.
x2 I run 3.70 gears, a .64 overdrive and 26" tire. I cruise at 75mph around 2300rpm. I'm considering going down to a 3.42 or even 3.23 gear for fuel mileage. But I'd like to keep the 70mph rpm to at least 2,000rpm.
