Gears: Speed and Track

Nick32Vic · August 15, 2005, 05:57:24 PM

You people are smart. I figure this is the best place to ask this.

The car
302 Ford from a 68 mustang
4 speed toploader (3 spd w/overdrive) from an 87 Ford F-150
9 inch ford rear end.
2.73:1 gears.

The Goal
To have a car that is great on the highway but can also show what it can do on the track. I will be driving it way more than racing it, but the hamb drags are coming up and i also need to take it to the local track after that and show some people a thing or two.

The Problem
The car is pretty quick off the line but when it gets into 3rd and O/D it just doesnt accelerate. In O/D it runs at about 1300-1500 rpm's, when i step on the gas it doesnt move and faster.

The Solution
This is where i need your help.
I need to change the gearing in the rear end.
What should i go with?

3.50?
3.55?
3.90?
4.11?
Anything in between?

I know a guy that says he might have 3.50 posi, he would sell me, would that work?

Theres also another guy that would Give me 3.90 open, but i kinda want posi.

So what should i look for?

Im late for work, Thanks!

Nick

34ford · August 15, 2005, 07:32:29 PM

Nick,

Here's a photo for you
bob

tomslik · August 15, 2005, 07:56:01 PM

"4 speed toploader (3 spd w/overdrive) from an 87 Ford F-150"

you haven't broke it yet!?!?!?!?
don't worry, you will.....

anyway, the 3.50's will work decent but the 4.10'd be more fun...

slocrow · August 15, 2005, 08:01:03 PM

Ah Nick, my poor impromptu, camera carrying son. Nitrous my boy, nitrous. And lets not count short a good 5 speed with a deep first gear for forward motivation, with a road type rear gear for the highway. We need to talk because you just need a nasty off the line combo to fool with the hordes............Your photogenic sleeper, Frank

Nick32Vic · August 15, 2005, 08:47:40 PM

Bob, thanks for the pic!

Tomslick, does my trannsmission suck? I hope not. haha. What would the car do with 4.10s? Off the line? On the highway?

O ya, i got like 31" tires on the back.

Quote from: "slocrow"Ah Nick, my poor impromptu, camera carrying son. Nitrous my boy, nitrous. And lets not count short a good 5 speed with a deep first gear for forward motivation, with a road type rear gear for the highway. We need to talk because you just need a nasty off the line combo to fool with the hordes............Your photogenic sleeper, Frank

HA! No thanks on the nitrous. I wish i could afford a good 5 speed when i was building the car. And you are right, you are a very photogenic sleeper.

Nick

enjenjo · August 15, 2005, 09:16:16 PM

Well, the 350 gear would be a good all round gear, but not the ultimate for racing. With an OD trans, a 390 gear will still be ok on the street, but much better at the drags.

The main problems with your trans is the aluminum case, and plastic bushings. Both allow too much distortion, causing the gears to break.

Pope Downunder · August 15, 2005, 10:34:01 PM

Quote from: "Nick32vic"You people are smart. I figure this is the best place to ask this.

The car
302 Ford from a 68 mustang
4 speed toploader (3 spd w/overdrive) from an 87 Ford F-150
9 inch ford rear end.
2.73:1 gears.
snip
Nick

Have a play here;
http://www.ringpinion.com/content/calculators/RPM.asp

I am not sure what the O/D ratio is in a TL; however this will give you a good idea.

Your probably below 1700rpm @ 70mph in OD at present.
With a 3.5 you would still be under 2200rpm (not a bad all round ratio)
With a 3.9 you would still be under 2400rpm (good all round ratio)
With a 4.11 you would still be under 2500rpm (still an OK ratio)

Depends what you want, I reckon the 3.9 is the go.

tomslik · August 16, 2005, 06:00:31 AM

Quote from: "enjenjo"Well, the 350 gear would be a good all round gear, but not the ultimate for racing. With an OD trans, a 390 gear will still be ok on the street, but much better at the drags.

The main problems with your trans is the aluminum case, and plastic bushings. Both allow too much distortion, causing the gears to break.

well, they wern't ALL aluminum and even the iron ones were junk...

AND parts are a * to come up with....
definatly not meant for racin'

rumrumm · August 16, 2005, 09:08:17 AM

I would grab the 3.90's. I have 3.89's in my coupe, and I like that ratio with an overdrive.

enjenjo · August 16, 2005, 09:28:02 AM

Quotewell, they wern't ALL aluminum and even the iron ones were junk...

AND parts are a * to come up with....
definatly not meant for racin'

I know, fixed a few of the cast iron ones too. Abusing it in reverse was a sure way to blow it up. I had one customer who would blow his up every few months. An idiot who would never listen.