T5 or T5Z? Whats the 1st gear ratio benefit?

[stangman67]

I was looking into a T5 swap for my 67, so I figured Id ask the people who deal with them all the time. Is there a reason why I should go with a T5 with the 3.35 first gear, or the T5Z with the 2.95. I have 3.55 gears currently, but may upgrade to 4.11 with either 5 speed. My car has about 350 hp and a flat 300 to 350 ft lb. torque curve. I wont be beating on it, so I think either tranny will do the job. I noticed the 3550 Tremec has a 3.27 first gear, so is that a reason why the 3.35 may be better? Thanks for the input.

 

[jd351]

T5Z will allow you to use first gear with those rear gears. The standard 3.35 first will be like a granny gear with 3.55 rears or bigger. Either way you will not be doing anything short of launcing in first, but the 2.95 will allow you more time to shift.

 

[Juiced88Coupe]

I have the T5z with 2.95 gear set and use 4.10's love it, 1st gear is killer with slicks here are the specs on mine
AG1 input 2.95 STD
AG2 cluster 2.95
AG3 3rd gear (30T)
AG4 2nd gear (33T)
AG5 1st gear(32T)
AK3 rebuild kit
AM21 6T speedo gear

 

[89MustangGX]

The 2.95 gearset is stronger, so if you want astronger tranny, that may be reason enough.

 

[Michael Yount]

There are other ratio differences between the two.

T-5Z - 2.95 1.94 1.34 1.00 .625
T-5 - 3.35 1.94 1.29 1.00 .675

 

[Michael Yount]

So for Launching, a T5 with 3.55 gears is VERY close to a T-5Z with 4.10 gears.

The overall ratio is 11.89 with the T5/3.55's and 12.09 for the 5Z/4.10's.

 

[cleanLX]

As Michael pointed out the T5z has closer 1-2, and 2-3 ratio's.
Provided your rear gearing is optimized to your combo, the T5z, being a closer ratio set, will net better 1/4 miles times by keeping the rpm drop between shifts less, thus keeping the engine in a more efficient powerband thru the 1/4.

the 3.35 of the T5 requires you really ring 1st gear out in order to drop back into 2nd at an rpm to take full advantage of 2nd gear, this usually means you'll hold first longer than your useable power band, but, since the time spent in in first out of the power band is so short in comparisson to the time spent pulling thru the bottom of second, it's the fast way down the track. Same happens on the 2-3 shift, you end up holding 2 a bit longer than optimal so the longer pull thru the bottom of 3rd is more optimized.

So, in reality, with the 2.95 gear, you're actually holding 1st less... at least when it comes down to rpms.

 

[stangman67]

Thanks for the replies everyone. It seems like ill just go for the Z and then i will have flexability for future upgrades and stregnth. Thanks again!

 

[Michael Yount]

To put Mike's comments in perspective, my car peaks HP at 4900, and torque at 3800. To keep the engine between those peaks as much as possible, with the T-5Z, my optimum shift points occur at 5500 1-2, 5200 2-3, 4900 3-4. This lets the engine drop to the 36-3800 rpm range on each shift and pull back from peak torque to just past HP peak. I could probably drop them a few hundred rpm without it making a whole lot of difference as my torque curve is extremely flat between 3000-5000 rpm. Actually it's just extremely flat everywhere. Actually, it's not a curve at all. It's a torque flat.

 

[dericjt89]

I have 89 gt with a b303 cam and 1.7 rockers. I broke 2nd gear in the t-5 I had so I went to the z and picked 3 tenths and 5 mph