Here is my happy little engine combo. Ive got a 1987 roller block, with a '77 rotating assembly (crank balancer flexplate rods) E303 roller cam. Sitting on top of the block is a pair of ported '75 351W heads with 60.4 cc combustion chamber, and 1.94/1.55 valves. The torque converter I am selecting has a stall range from 2000-28000 and of course that depends on gears and torque output. The problem I have is that this car is supposed to be used on the freeway alot and I dont want to sacrifice gasmileage and engine wear for lower gears. People have told me because the car is light, that it should perform fairly well with the 2.79s. Any thoughts? Also is anyone using 2.79 gears with a modified motor? If so how are u doing. Also I might be able to convince myself to go with 3.0s anyone running them?
The 2:79 was the standard ratio in the 8' rears. The 3:00 came in many Grabbers with a factory 302. While they work adequately for cars with the 6s like mine, I have to wonder if it may be a bit light for a modified 8 like yours. They might not like being pushed by a more powerful plant. My suggestion would be to go with the 3:00.
I originally had a 250 in my Mav with the 2.79 gears and I found that when I went to a stock 302 the gears had no problems handling the power difference but I did find when I changed the rear axle gears (3.55) it made the car drive a hole lot better in my honest opinion and gas mileage wasn't to off from what I was getting before. It really all depends on if you like to hammer the throttle or are gentle with it. I got better gas milage out of a 80 Trans Am with a 350 BB (4.10 Gears) than I did out of a 95 Jimmy with a 4.3L (3.55 Gears)
gears with a 2000-2800 stall I would not run less then3.55 gears. with the higher gears theres a good chance of slipping the converter cruising rpm would not be high enough.just my $.02
I ran almost the exact same engine in my '74 for a while. I tried 2.79's (stock), 3.00's, 3.55's and 4.62's, all on the street. The 3.00's were the best all-around gear but of course the 2.79's were nicer on the freeway @ 70 MPH. The converter was a 2800-3000 TCI that performed well, but the trans cooler saved the trans from overheating. The 3.55's were too much for the turbo-torque, and 4.62's were a LOT of fun in third gear, but 1st & 2nd were useless, and the motor was out of steam by 80 mph (5000 rpm max).
Madmav74 makes an excellent point. You don't want any stall slip on the highway. To take advantage of those mods, you should probably go to a 3.25, if you can find them.
One question I have is why do people put really low gears in there cars if they are planning on just running street radials. The first thing i noticed everyone does is put low gears. Is it because it is a cheap mod? The reason I ask is i have talk to people who complain because they can't get traction yet they have 4.11 gears. Do people add the low gears with the belief that they will be able to get all that torque to the pavement? I know for sure my car will not ever have drag tires on it. So if I add these 3.25s or 3.55 am I going to be able to even get enough traction to make them worth while. I guess the question is which case is better, to have low gears but burn the tires some or have slightly higher gears and maybe not loose traction as bad? I may be totally mixed up here. My opinion is that it is better to have higher gears and not loose traction as much, but I have no real drag racing experience yet Any thoughts?
traction my mav had 3.80 gears and 245/60/14 tires with some universal slapper bars traction is not a problem if you use a little common sense, if you stand on it, your gonna break'm loose. I've even drag raced with this setup with minimal traction probs. As of now it will be more race then anything so i'm going with 4.62's and 28X10 slicks
Be careful with too much gear. I was running 2.73's in my 5.0 86 stang, and finally switched to 3.73's. Now keep in mind that this is a 5 speed car. The rpm's jumped considerably. Where I used to spin 2000 rpms at 80 mph, I spin more like 3000 at 80. When I had the 2.73 gears I had no problems running a low 15, hi 14 second time slip all day long, and that is with a heavy vert weighing about 500 pounds more than the mav. If I were you, and you do a lot of freeway driving, and don't have a t5 or aod on that thing, I wouldn't go past 3.00. Sure you can do it, and sure people do it all the time, but the comfort level goes down, and driving becomes a chore. I love my 3.73's but am happy as hell I don't have to drive them everyday, as I do a LOT of freeway driving to and from work.
That is an extremely good point worth considering! Case in point, my old '83 Ford F100 w/mild 466 ran some low 11's in the 1000' with 3.89 gears. I got tired of running 3000 rpm at 65 mph on the highway (especially with the 466!) and swapped in what I thought was a set of 2.75's. They turned out to be 2.47's later when I removed the chunk and put 3.00's back in. The truck ran faster in the 1000', had a better 60' and best of all, only turned about 2300 at 65 mph. Granted I was only using 1st and part of 2nd gear (crossed finish line at 3200 RPM in 2nd) but traction was the reason it was quicker. Leaving the starting line with 3.89's was a challenge at best...and anything past 1/2 throttle in 1st gear was useless. I miss that old truck....or better yet, I just miss the big-block.
The other question I have is about using a higher stall torque converter with higher gears. Someone previously posted that I will not get full lock up on the freeway with such high gears. It makes sense with a mustang or heavier car, but is it going to happen with the lighter maverick? Does anyone think it is bad to use a higher stall with higher gears?
