4.10 FTW

 

You have the ability to answer the question of what gear ratio will work best for you. Don't simply listen to some dork that says you "need X.XX gear because they ROCK!" For all you know they are borderline brain dead. Just because they don't mind driving around with the motor spinning to the moon doesn't mean you won't.

This is the most important information you need before making your own choice based on your situation:

What RPM’s do you want to be cruising down the freeway at and at what speed. Think about that hard, and go drive the car. Drive it for 2 miles at 3,000rpm…..it will most likely drive you crazy. If it does, you want to make sure you don’t get a gear that will put you in that range. I have mine set up to run at 2400rpm’s@80mph. I wouldn’t want to spin it any higher than that even if it costs me a bit of acceleration.


Depending on what the height of your tires have I'll bet you will want 3.55's or 3.73's to get a comfortable cruising RPM.

I run a 3.55 and couldn't imagine wanting to gear my car shorter than it is. I do have a screw blower though. 1st gear is worthless, I just punch it and have to shift right away and 2nd gear will haze the tires even though I have some seriously sticky rubber. Shorter gearing wouldn't get me going any faster....faster. It could possibly even slow me down.

Even if you don't have a blower but have stock-ish tires (high performance, all season about 235-245mm wide) you will still light the tires up something good in first and have to go for second super fast which makes that gear borderline useless. You will still lightly spin the tires most of the way through second too (if you make the 1-2nd gear shift fast) which lessens the effectiveness of that gear too. Which will slow you down.

When I had my stock 3.31's and stock Pirelli tires (about 75 miles ) I could SPIN the tires all the way through 2nd gear if I wanted too.

Use this gearing calculator. It will help you pick a gear for your situation. Use the # .71 for the auto trans ratio and .68 for the 5 speed. You will also need to measure the height of your rear tire at the right pressure sitting on the ground. You can keep firing numbers in till you find the gear that gets you the cruising RPM that you are looking for.

http://www.angelfire.com/fl/procrastination/rear.html

 

Scott u driving that thing yet?

 

The pot said to the kettle... "I think that we found the dork."

 

Well yes I am. But like most of YOUR mods I am running into a few issues. The gears are in but after they did the gears yesterday and went back under the car this morning to do the fuel filter they noticed a small leak at the pinion seal. So they got a new seal and replaced it today. So far it looks dry after about 50 miles of driving. I will keep checking. So I got home tonight and loaded my new updated tune from Brenspeed. Well while the car is still drivable the only thing they did correctly was get the speedo right. My total shift schedule is hosed up from what is was set at before. Been on the phone with them and they will make it right but not until next Friday because Brent and the gang are out of the shop racing this coming weekend. I just emailed them everything I want and they will email me a new tune. I figured out how to download to my dinosaur tuner. Anyway the car is drivable but it is hard to tell the real benefit of the 4:10's the way the trans is shifting now. My car goes from 3rd to 4th into overdrive all in the span of 4-5 mph. And that is between 42 - 47 MPH!!! But it cruises great on the highway and my rpm/mph reading are a little higher than yours but I think that is because my Nitto's are about 1/2 inch smaller diameter than stock. Cruising on the highway wasn't bad at all. And best of all the gears are completely quiet. Here is my readings.

55 mph - 2100 rpm
60 mph - 2350 rpm
70 mph - 2600 rpm
80 mph - 2850 rpm

I'll work out the bugs in the coming week. But my installer is great and didn't charge me a dime yet until we are sure everything is correct. And yes I saw the bill today so I know what the cost was before the pinion seal leak. He won't hose me.

P.S. Well said Steeltownstang!!!!!!!!!

 

Lmao. I was gonna say it was quite the read for a 5th post.

 

Well those numbers are pretty close. Only 100 rpm difference.

Sounds like all these shift points are screwy after the gear install. Chris was supposed to have my update today but nothing yet. I switched back to his all out tune and changed a few things via the X3. All seems good and no slippage at 30 and 60 like I mentioned b4.

So what all did you ask them to change/adjust? Good to hear your installer isn't charging yet.

Sounds safe to say your happy with the ratio tho?

 

I hope that you get those kinks worked out soon Scott. I know that it can be frustrating. Good luck.

BTW, 4.10s ROCK!

 

Thanks guys.....Oh I have been down this road with mods before and I know I will get it all worked out soon. In the mean time I have to put up with what I have until the brains at Brenspeed get back from racing. I trust them completely to make the tune right. What I want and had before was this....

1st -2nd shift at 3000 rpm
2nd -3rd shift at 3000 rpm
3rd - 4th shift about 2500 rpm
5th gear (overdrive) comes in at 55 MPH
Once in overdrive and going on the decel it would drop back into 4th gear at 50 mph. This is what Brent @ Brenspeed was running in his auto car back when I had the cams done in Feb 2008. It makes it feel very close to what manual car shifts like. I just want it back!!!

 

Hi Scott, glad to hear you at least got those gears in finally. I'm sure your tune issue will be taken care of.

 

Thanks Tom...I know it will be taken care of. Send me a pm on how your new world is going!!

 

Yea no kidding, what a wuss!

Tim

 

Got my updated auto tune yesterday from Brent and it is very close to the way it shifted when I had the 3:31 gears. He explained that when you go to 4:10's it really hoses up what he can do with the individual gear shift points. But he can move the entire shift schedule up and down by percentage. So his best guess to get me close to what I had was to move the schedule up by 20%. That got my OD shift point back up to about 53-54 MPH or so. But it also moved my 1-2 and 2-3 shift up to 3500 rpm. I like it. Pretty aggressive feeling. Should be enough to keep the wifey from wanting to drive it.