3.89 or 3.55 gear

Hi everyone, I know its been covered a million times but I would like some real life reviews on these gears from users that have went either route.basically I want to know which wouldwork best for my combo and why.ANYWAYS the car has a 351c 4v and toploader 4speed although im not certain on wide or close ratio.motor is mildly built top end with a edelbrock torker intake and more than likely a 750 demon.I will be running a 285/40/18 tire in the rear which equals out to 27". the car will be occasional city driving, to and from shows and on the highway a small amount.so go ahead and persuade me either way..

I basically have the same set up including the 18's. I just removed the 3.91 and replaced with 3.25 for the Hot Rod Power Tour. I think I would be happier with the 3.55's however.

Did you only switch to the 3.25 for the tour itself? How much acceleration did you lose out the hole changing it out?

The standard factory ratio is 3.25 for a top loader and 4v engine car which is what is in my car. I really like it and think it to be perfect for a car without overdrive. I do a mix of highway and around town, but no racing. The 3.5 will get you off the line a little quicker but higher rpm at highway. In my opinion the 3.91 would be way too much for any car without overdrive on the highway unless you like driving at 55mph.

See the trans gear ratio thread for more info.

Steve,

I am running a 3:50 gear, top loader & 27" tires on my car. Around town is good but on the high way its running around 3,000 rpms @ 60 mph. I do like the way it runs, but I wish I had a 5 speed !!!

Thanks, Jay

I run 3.56 in my 73 302 fmx SR. I think its just right. I don't drive it more that 45 miles to shows. It also has antigue tags anyway. That limits use anyway. I think it came with 2.73, and I drove it x country like that. Now it will jump off the line, never would before.

I have a 65,298hp,4sp,3.50 rear, I think the 3.50 gear there is just right also.

My buds with higher gears usually swap them out in a year because the rpms are just too high going down the road. None of them have overdrive.

For overall drivability 3.55... for track duty 3.89. If you're not planning on racing the car go with the 3.55 maybe even a 3.25.

If you're even thinking about an overdrive trans swap the 3.55 will be the better choice. I'm running a 5 speed and the stock 2.75 gear, it cruises at about 1700 at 70 mph. I'm also running a 285-40-18, the plan is a 3.55 or 3.73 gear that would put the rpm at either a little over or under 2000 at 70 per the calculator with my T-5 trans.

3.55 is a good all around ratio. 3.89 is fun but will become a chore in much shifting in traffic and too-high RPM on freeway runs.

3.25 is great for street driven...lags just a little for performance though.

I had a '79 Z-28 with 4-speed, 3.73 gears. Loved it. Drove it 70+ MPH on freeway over 100 miles many times without issue. When I sold it, the buyer called me soon after wondering how I could stand driving it on the highway after 5 minutes.

To each his own. Do what you like.

Kit is spot on I just swapped out the 3.89's that were in mine. Great gears if you want to get off the line quick but the RPM's got way to high to fast and casual driving was a chore. I have multiple carriers now one with a 3.70 and a set of 3.55's also and really like the 3.55. It is a great in between gear comparatively speaking. Car has a nice bit of pep with reasonable drivability.

My car came with 2.75 rear end and a FMX tranny. I swap pen an AOD with 3.89 and ended up with the same RPMs at freeway speeds.

If you top gear is 1:1 I wouldn't go any higher than 3.55:1

If you're even thinking about an overdrive trans swap the 3.55 will be the better choice. I'm running a 5 speed and the stock 2.75 gear, it cruises at about 1700 at 70 mph. I'm also running a 285-40-18, the plan is a 3.55 or 3.73 gear that would put the rpm at either a little over or under 2000 at 70 per the calculator with my T-5 trans.

Click to expand...

Ah Ha!! at last I can figure out why Jeff with a 351 Cleve and 5 Speed got better fuel milage, than we did 306 and 4R70W. It was the 2.75 vs our 3.25 that made the difference.

My preference on gearing with an OD trans is 325 for all around. And 3.55 for around town. When I get the EFI on the 73 I may change it to a 3.55.