If it will be daily driven, 4.10s would be the absolute max I would go, and honestly I would consider stepping back to 3.73s, especially if you do any highway driving at all. Before doing any gear swap, drive around with OD locked out for a few days. That will give you similar cruising rpms as 4.10s.
I have 4.10 gears still in the box I've been meaning to install in my car. From my research 4.10's is pretty ideal for street driving. 4.30's may be a bit much for a daily driver. It would be a good idea to put in an aluminum driveshaft and rear lube mod on the trans when you go into the 4's for gears.
I think it really depends on where you commute daily. If you are in an urban/suburban setting or in the twisty hills, 4.30s would be just fine. If you are on the open highway at highway speeds very much, I would have to say 4.10s.
What distance is your typical daily drive and at what speed?
3.73's would be my go to gear for a daily driver. I wouldn't go higher than 4.10, but as tbirdtess mentioned 3.90's are a good in-between.
Speaking from experience, switching from 3.73's to 4.10's helped my track times but my top end is now very limited. 4.10's are not a highway friendly gear at all and 4.30's, IMHO, are a track only gear.
Speed of course. You sacrifice a lot of top end speed with lower (numerically higher) gears because they push the RPMs up so much faster you end up running into your engine redline. My car tops out around 130 MPH in 3rd gear at my redline of 7,000 RPM with the 4.10's. At the stock redline of 5,500 RPM top end would be around 110 MPH or so. I learned the hard way not to to do top speed runs in OD because the OD band burns out.
I don't have the spreadsheet handy, but GM sent me an excel spreadsheet that does all the calculations for various gear ratios and MPH at various RPM speeds.
But in the words of Sammy Hagar, I can't drive 55! Traffic around here is usually running around 80mph, and with 4.30s that puts you at 3100 vs 2700 with 3.73s. That makes a huge difference in terms of the comfort and noise level inside the car.
I've driven both 3.73s and 4.10s for a number of years each, and ended up switching back to 3.73s. They make the car quieter and less busy. Plus, by switching to a shorter drag radial I really didn't lose anything at the track.
Both of the following are only 100-150$ more expensive than me going and getting a used one out of the yard and buying all the rebuild and add-on parts.
Has anybody used either of these in their mark viii or t bird?
There is this...
Upon finding n buying my old Cougar, I noticed immediately a fact I had ignored for 25 years... and all of you guys knew all along.... a 94 4.6 Cougar is a great 3400 pound factory v8 hot rod..
its got the torque, the horsepower, the solid transmission, heavy duty indi rear end four discs, rack...
Alright so one piece driveshaft from the lincoln is on the way thanks to CDsDontBurn. Plan on trying to do the gear change at the same time just looking for some guidance on what all i need to attempt it myself. I know i need the 373s, the limited slip unit, speedo gear, also going to replace...
So I always had the impression that 94-95 Tbirds only had 3.08 rear gears. I was under that impression because the 96-97 cars had 3.27s, and In a TCCOA tech article comparo (see this) states something along those lines. Well my local pull it junky yard had a 40% off weekend so I went out...
Any reccomendations for which gear box to put in my '97 Cougar? Ive heard '03 bolts right on but I may be misremembering.. Any modifications required or should I just put gears in my OEM gear box??
Stage 2 cams will be ordered soon and very likely a torque converter to go along with..
A forum community dedicated to Ford Thunderbird, Mercury Cougar and Lincoln Mark owners and enthusiasts. Come join the discussion about performance, modifications, troubleshooting, maintenance, and more!