Changing Transmission Gear Ratio?

[Damien214]

OK I went down to my local tranny guy and he told me that changing the 4l60e 4th gear from .72 to anything else was impossible. Is this true? I know the internal pieces of the 4l60e are almost identical to the 700r4, do they make different ratio gears for that? Has anyone else done this, or does anyone else know if this is even possible. If it's not, I'm drastically deciding whether or not to keep my car. A T6 would be great, will this mount up to the 3.8? I want a fast 1/4 and great gas mileage with a high top speed, so a T6 LT1 may be in order if I can't figure this one out. Are there any years or model 4l60e's or 700r4's that have lower ratios than .72?

[Damien214]

Well I found out how to do it. I have to go with an external electronically controlled unit that will require a custom shorter driveshaft as well. The cost is $2300 plus unknown in custom fabrication, the good news is I will be able to switch from 3.73 equivalant rear to 3.08 equivalant rear with the push of a button. The unit reduces rpms by 22% and increases top speed by the same, not considering aerodynamics of course. I'm finding out the hard way why supercars cost what they do, but hey I'm gonna get one of these hopefully for less than that, but I will pay $2300 if I HAVE to. Anyone know of a place to get them cheaper, please speak up!

[Jason McCallister]

<blockquote>quote:</font><hr>Originally posted by 10SecDream:
OK I went down to my local tranny guy and he told me that changing the 4l60e 4th gear from .72 to anything else was impossible. Is this true?<hr></blockquote>

It is true. The automatic transmissions use a "planetary gearset" in which this 1 set of gears simulates 4 individual gears. The only way to change the final OD ratio is to change ALL the ratios. :(

Here's a GREAT website that explains the automatic transmission and how it works. Read this and you'll understand why it's impossible. ;) :D

[MustangEater8251]

Are you doing this jsut for fast acceleration, and more top end? Or jsut to save gas?

Cuase you are spending $2300 to save $500 in gas.

I am pretty sure there is no way for the t56 in F-bodies can bolt up to 3.8L, I know they cannot to 3.4L. But ther is a 6-speed that can, I forgot the name of the company but its like $2k for it. May want ot look further.

I considered upgrading to a 6-speed since my 5-speed is pretty much crapped out and getting worse.

[Damien214]

not even that in gas money, I want it for the top speed back and I will actually have 8 total gears, so I will be able to get to top speed much quicker due to the closer ratios.

[HAZ-Matt]

[QUOTE]Originally posted by Jason McCallister:
[QB]

The automatic transmissions use a "planetary gearset" in which this 1 set of gears simulates 4 individual gears. [/B]

Actually, each planetary set makes 2 different speeds... so linking two planetary sets together gives you 4.

10secDream: Will you really have 8 total gears, or will it just use the 3.73 ratio until your done in 4th, then switch?

[ January 24, 2002: Message edited by: HAZ-Matt ]</p>

[Damien214]

It will be 8 because it can switch any of the 4 gears, but i've decided against this because my safety loop and torque arm would have to go and with my HP goals that could be a death sentence.