mooch1

hi , i went from a 700r4 to a T5 ,, both with 3.23 rear posi gears,,i found with the 700r4 and shift kit the launches were more quick ..i also noticed it would rev less higher on the hi-way with the R4...would 3.42 or even 3/73 gears a better idea?

sofakingdom

iTrader: (1)

The launch thing sounds like driver issues.

The other, it depends on which version of the T-5 you got. If you got the good one, that came in the high-performance cars (L69 or TPI), it would have a .73 5th gear, which is arbitrarily close to the same as the 700's 4th. If you got one out of a base-model low-perf car (LG4 or L03), then you got a .63 5th, which is wider than the 700's OD and makes the car feel at times like you need another gear between 4th and 5th... they did that I would assume, for the last possible .0001 mpg to help with CAFE. The low-output slow cars that were bought by people who didn't care about, or wouldn't notice their lack of performance, were the CAFE "sacrificial lambs". Sounds like your T-5 came from one of those that got the inferior one.

As far as which rear gear would be better, if your motor makes power at high enough RPMs to where you won't have the classic "tractor motor" effect (will pop wheelies but can't pass a broken-down dump truck especially going up hills) then they'll do you some good. In these cars, about the only motor that really shines with 3.73 gears in stock consition, is the L69. All the others, the torque falls off too fast with increasing RPM. If your motor is significantly modified (no, I don't mean chrome exhuast tips) then the situation is a bit different.

mooch1

hi, it feels like i need a gear betwwen 4th and 5th like you say..i guess i have .63 last gear,,but it is a WC T5..has the timken bearings cap out front on the input shaft,,the launches are ok , i haven't pushed it too much ,,i have a 350 with 4 bbl 1405 edelbrock carb, 1500 rpm edelbrock intake ..rough idle cam(don't know specs),,headers, no cat ..no egr and no smog anti-pollution anything,,it has a lot of power at low end ..i was just wondering if 3-42 0r 3-73 gears were mosr suited for my engine rather than the 3-23's....

sofakingdom

iTrader: (1)

Yup... both 1st and 2nd design T-5s came with both gear combos. No guarantee of suckage, or lack of it, with either revision.

Take your car to the dyno and get your torque curve. That'll help figure out where it makes power. That's the best way to pick the right gear. Nobody out here can tell stuff like that, at least not without motor details (cam part #s, head details, exhaust, intake part #, etc.).