Changing Gear Ratio On A T5

[Davedacarpainter]

@90sickfox just posted on another thread about gears and it included a website to www.thegearbox.org.

I need to eventually rebuild my T5. If i wanted to change the first gear ratio, is it really as simple as changing out the first gear for a new one?

 

[90sickfox]

No, you'd need a matching cluster gear....I think

You've given me something else to research....

 

[Davedacarpainter]

I am beyond ignorant in this, any information will be helpful.

 

[droopie85gt]

First gear is part of the main input shaft, as I recall. The cluster has to match too. Google a T5 rebuild and you can see the guts. I think there's 3 main 1st gear ration. 2.95:1 for the Z spec. The other is 3.35 for the normal world class box. I think 4 cylinders had a 3.97:1!! first gear.

 

[General karthief]

I am beyond ignorant in this, any information will be helpful.

A few coats of paint and some wet sanding will NOT take up the slack with a different gear ratio.
Just say'n

 

[droopie85gt]

http://www.mustangandfords.com/how-...ever-wanted-to-know-about-the-t-5-five-speed/

Here you go!

 

[imp]

I am beyond ignorant in this, any information will be helpful.

The mainshaft (or input shaft, sometimes called), must necessarily have more or less teeth (depending on your intended ratio change), so it's diameter must change. For that reason, the matching front gear on the cluster gear must also change diameter, in order to match the meshing of teeth properly.

FWIW, failure of manual gearboxes is very often due to "spreading" apart of the meshing gears due bending forces in their support shafts, as well as the transmission case itself. For that reason, all other things the same, iron boxes tend to be stronger than aluminum alloy. While there are indeed "aircraft" aluminum alloys, such as 7075-T651, which is stronger than cold-rolled steel, but unfortunately the "strength" refers only to tensile strength and not "hardness" strength, which simply means strong aluminum still deforms more than steel, regardless of it's tensile strength.

I do know of one gear ratio easily available for T-5s other than the usual used by Ford, but unfortunately it is only for 5th. gear (overdrive). That was used by Jeep in T-5s mated to small Dana Transfer Cases I believe in the early '90s. Used those Jeep gears when I built my '70 Bronco w/ 5.0HO and T-5. Here's the look underhood:

The metal can connecting the Mustang rubber inlet duct to the TB was chosen for size by measuring foodstuffs in a big supermarket! Below, the truck before I gave it to my nephew, who restored the body.

 

[Mustang5L5]

1st gear ratio is a combination of gear teeth counts between the input shaft, the countergear, and the number of teeth on 1st. The diameters are specific, so changing gears requires a slight change to the mating gear, so as a result, most gearsets are sold in a set consisting of 1st, 2nd, 3rd and a countergear and input shaft.

Other than the very early non-WC gearsets, the lowest T-5 gearset available is the T-5Z spec with the 2.95 1st gear. Buying a real tremec set is VERY expensive, although it's a bit more manageable with the aftermarket gears many are making these days. Astroperformance is selling a Z-spec countergear for $100 for example (aftermarket).

Add up the cost of all the gears, and it may cause you to rethink it however. Rebuilding T5's used to be cheap, but now it's not anymore.

I have a parts T5 that I'm strongly debating a 2.95 gearset build with, but I should really go with an astro performance build.

 

[droopie85gt]

The biggest stepup the z spec got was a real bearing on the input shaft, not those 13 (I think) individual roller bearings. I have a completely disassembled t5 in a box with a rebuild kit and a reconditioned input shaft that got roached where the input shaft and those rollers gauled it all up. I was gathering parts when one day on CL there was a new IN THE BOX T5Z that I got for $1100. I would trade that (less than 2000) miles for a needing to be rebuilt 3550 or TKO500. I fear I may need a little more for my 351 swap.

 

[imp]

1st gear ratio is a combination of gear teeth counts between the input shaft, the countergear, and the number of teeth on 1st. The diameters are specific, so changing gears requires a slight change to the mating gear, so as a result, most gearsets are sold in a set consisting of 1st, 2nd, 3rd and a countergear and input shaft......

My goof-up. I saw his wording "main input shaft", and understood him to be referring to the INPUT shaft, which engages the clutch disc, and provides the drive for the cluster gear. "High" gear is picked off the input shaft, which connects it to the MAINSHAFT, which is the output shaft of the transmission. Sorry. imp

 

[General karthief]

I hope you don't get your 'shafts' mixed up too often

 

[imp]

I hope you don't get your 'shafts' mixed up too often

I could be described as "shaft-happy", considering the ones I had to splice together to mate a top-loader mainshaft to a B/W HD O/D input, and a Dana 35 Transfer Case input.........imp

 

[MFE92]

Upgrading the standard 3.35 1st gear to the higher strength 2.95 1st gear requires a change of at least the 1st gear AND the cluster gear. I can't recall 100% correctly but I'm pretty sure other parts of the gearset require changing with the cluster even if their ratios are the same. It's not a cheap upgrade.

 

[Davedacarpainter]

So changing out first gear is a little more extensive than I might desire.

 

[Noobz347]

My goof-up. I saw his wording "main input shaft", and understood him to be referring to the INPUT shaft, which engages the clutch disc, and provides the drive for the cluster gear. "High" gear is picked off the input shaft, which connects it to the MAINSHAFT, which is the output shaft of the transmission. Sorry. imp

Whenever you think 5L5 might be wrong? Read it again because it doesn't happen very often.

 

[deathb4dismount]

The biggest stepup the z spec got was a real bearing on the input shaft, not those 13 (I think) individual roller bearings. I have a completely disassembled t5 in a box with a rebuild kit and a reconditioned input shaft that got roached where the input shaft and those rollers gauled it all up. I was gathering parts when one day on CL there was a new IN THE BOX T5Z that I got for $1100. I would trade that (less than 2000) miles for a needing to be rebuilt 3550 or TKO500. I fear I may need a little more for my 351 swap.

I didn't think the 3550 had a longer first gear?

 

[FoxMustangLvr]

1st gear ratio is a combination of gear teeth counts between the input shaft, the countergear, and the number of teeth on 1st. The diameters are specific, so changing gears requires a slight change to the mating gear, so as a result, most gearsets are sold in a set consisting of 1st, 2nd, 3rd and a countergear and input shaft.

Other than the very early non-WC gearsets, the lowest T-5 gearset available is the T-5Z spec with the 2.95 1st gear. Buying a real tremec set is VERY expensive, although it's a bit more manageable with the aftermarket gears many are making these days. Astroperformance is selling a Z-spec countergear for $100 for example (aftermarket).

Add up the cost of all the gears, and it may cause you to rethink it however. Rebuilding T5's used to be cheap, but now it's not anymore.

I have a parts T5 that I'm strongly debating a 2.95 gearset build with, but I should really go with an astro performance build.

I just checked in to the A5 rebuild kit and it seems to be on a long back order. I heard there is an issue with the company that makes the gear sets for Astro. Something about a son taking over the company and screwing things up for Astro.

 

[2000xp8]

My question would be why do you want to change the first gear ratio?
On a lower powered car (not saying yours is) the longer first gear robs the car of some fun.
I had a t5z and have a tko600, when the car had much lower hp, I didn't like either, so much so that before the terminator conversion I was going to goto 4.10's to compensate.

 

[deathb4dismount]

My question would be why do you want to change the first gear ratio?
On a lower powered car (not saying yours is) the longer first gear robs the car of some fun.
I had a t5z and have a tko600, when the car had much lower hp, I didn't like either, so much so that before the terminator conversion I was going to goto 4.10's to compensate.

Because at the magical 300ish to the tire first gear is pretty much unusable.

 

[Davedacarpainter]

My question would be why do you want to change the first gear ratio?
On a lower powered car (not saying yours is) the longer first gear robs the car of some fun.
I had a t5z and have a tko600, when the car had much lower hp, I didn't like either, so much so that before the terminator conversion I was going to goto 4.10's to compensate.

That's kind of interesting. I was thinking along the lines that the sc engine will have too much torque for that 3.35 first gear.

Kind of a moot point though, I'll probably get a TKO transmission to handle the torque anyhow.