kalli

well put it this way. the 3.5:1 is streetable and good with gas mileage. what you will gain with a 3.8:1 is more oomph oin accelleration. I'd say your engine should shred the tyres anyway in first gear, no matter if 3.5 or 3.8
but that said, if you thought you were going 85 where in fact you did 60, then I'd say you had a false impression on what the car is doing and what it will be

i wouldn't change the gears, only if you have to, but you said you're noisy in the back first day.

you not happy with the 256 cam we recommended?
the rpm is revhappy, makes power up to 6500, but we didn't recommend it (at least I didn't) as I don't know what your bottom end looks like.
You might end up spinjing it to 6500 and the pistons go flying


Kalli

MBDiagMan

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What some folks might not be taking into account is that the T5 has a lower low and a higher high than a four speed that would have come in this car from the factory. That makes for a spirited power application with a 3.50 gear compared to a 3.50 rear gear as Henry would have put it together.

_Remi

Thanks for all your input, it was more of a general discussion to help a buddy of mine. We always read that the best ratio is 3.50 for a T5 and I am just saying that it may not be true with a Performer RPM package.

Kalli, that's what you had right? How was your 5th gear below 2k?

Gun Jam

A "best ratio" for a t5 is highly subjective based on ones needs and driving style and engine specs.

With that engine a 3.50 might be best if you drive between Ca and Nv and typically do 90 mph for extended time periods on desert roads.

But that 3.50 might be way too high for someone who never sees freeway never sees speeds above 65 and drives only around town and wants the engine in its power range and runs sticky tires for him a 4.56 would be best.

In your case its simple you have 3.55s right now and they feel a bit doggy and you would like some more kick out of it then a 3.80 would be a great choice so would 4.11s. While the 4.11s might be in the tolerable upper limits the 3.80 would be dead on so you have to make a choice based on your driving conditions.

-Gun

phutch11

I think a valid argument could be made that actually the 3.80s could yield better gas mileage at cruise than the 3.55s with that cam, assuming that your headers, manifold, and carb support it.

An engine's brake specific fuel consumption its most optimal at the engine's torque peak.

Given that those 3.80s push the operating range of the engine closer to the torque peak at cruise you may see an uptick in mpg, or at least not as much of a reduction as you might think.

I will allow that engine friction will be higher but I think that a back to back comparison of same speed, same road grade would surprise you.

This is all at cruise though....overall mpg will probably go down as you enjoy the new acceleration potential of the car!

tx65coupe

I have a similar setup to that and I have 3.50 gears. I think its great. Sometimes I think it would have been nice to go with 3.70 though.

THUMPIN455

You have a Ford. Pick up another center section and put the 3.80 gears in it, or get two more and set up some 4.11s as well. You can then swap things around as you like and see what the difference is, if you find you dont like or want one, sell it and get your money back.

The option I like is building a bigger engine that makes more torque at a lower rpm so you can run a 3.00 gear and still run low 12s to high 11s..