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Here is some 3.73 feedback from one of our members:

Having upgraded from 3.27 to 3.73's, the effect was not as profound as I would have thought. I thought the low end would be a lot stronger. The real deal is that you spin up faster to hit the power band. Different from what I expected, but not bad. The car does pull harder once it spins up a bit to 2,000 RPM or so. The 1-2 shift is very strong on a WOT run. It's like the power band is accentuated.

I like to drive in the city in a higher RPM, and I find the lower gears are a good complement to my higher shift points. Driving with the OD turned off on keeps me in the 2000 - 2500 RPM zone. I actually find myself using OD more now when I am on a long stretch of road. So far gas mileage is about the same, but I'm using OD more in town than I did before. Clearly, highway OD will suffer.

The computer will try to shift into 4th / lockup at 34 mph, in lieu of the old speed of about 42 mph. Then the transmission will "hunt" in and out of 4th gear. My solution is to simply lock out 4th gear at speeds below 45 mph with the button on the shifter, when I'm not on the freeway.

Automatic downshifts come less easily / frequently now. I find myself keeping 3rd gear around corners now where my 3.27s would have found me in 2nd gear with the same pedal pressure/position. That's kind of a drag. But if you do push the pedal to force the shift, it's like shifting into 1.5 gear (if that makes sense) and the car really takes off.

The motor RPM's will go up by 21% from 3.08 to 3.73. So if your car was turning 1,800 RPM at 60 it will now be 2,175 RPM. With 4.10's it would be turning 2,400 RPM (33% difference).

I would recommend a good transmission cooler, installed downstream of the radiator in the return transmission line. You will work the car a lot harder when you change the gears, mainly because it's so fun that every stoplight will become a "Christmas tree".

My shift points are a bit higher than they were before both at part and wide open throttle. WOT shifts are 5,500 - 5,600 RPM (I know A-train, I know!). The car pulls hard to the shift point too, where it used to be pretty flat from 4,900-5,400 RPM, especially when it got warm out.

I wish the weather at the track had been as cool as my last time out!
Running a 15.4 with 3.73s after turning a 15.1 with 3.27s was disappointing for sure! But considering the 15.4 came at around 80 degrees and over 80% humidity, and the 15.1s came at 60 degrees and probably 35% humidity, it really makes sense.

My MPH stayed about the same on the runs by the way. I ran a best of 92 MPH on a 15.42.

All in all, I like the gears. My highway RPM is only increased by about 300 RPM. Engine braking is increased when I take my foot off the gas. Car feels quicker. Theoretically I will be able to go as fast as I want to (130 limit is okay with me).

The only problem is this damned driveline critical speed issue! I must get past this vibration. The cure may cost more than the rear end! I'll get my shaft balanced and see what that gets me, but critical speed is critical speed regardless of balance and trueness. An MMC driveshaft can go 6,300 RPM for the low cost of $480! That would work, so I may just save my cash and drive nice until I can get the super shaft!

I would not feel too bad about going back to my 3.27s though. The traction lock has been the biggest improvement IMHO. I literally spun my last set of tires off my car, mainly spinning the inside tire during cornering. It is much harder to spin them now. If I go back to 3.27s it will be with a traction lock differential in the pumpkin for sure!

Dan Ulrich
 
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