Need a rear gear ration recommendation...

Back half Fox Mustang, 32x14 slick, 514 with a glide. I'm thinking it needs a 4.30... What's everyone else think? Someone told me to stick a 4.56 in there, but I think it's too much...

I run a 31.25 high growth tire and 4.57 for the 1/4 mile stuff, reg 31" tire and a 4.86 for the 1/8th

For your combo either would be fine.

1/8 or 1/4? i could'nt be much help for 1/4 but 1/8th mile a 4.56 should be a real good place to start.how many rpm you want to turn it? i run 15x33s with 4.86 gear for 1/8 mile and lots of people with sb/glige combos run 5.13s.

We ran the 4.57 gear behind our 514/'glide with a 17X33 tire. Good compromise for both the 1/8th and the 1/4.

4.57's I would think would be hard to go wrong with. Don't think 4.30's will give enough RPM through the traps 1/4 mile wise.

JMO

Jon ,

I ran 4.30's with my 29.5's Shifted at 7100 crossed the 1/8 at 6700 1/4 at 7000-7100. 147-148 mph

4.56's I think would be good.

Jon

I had 456s in the old car with the same tire Blake is running.My motor is a 492 and it would fall on its face at about 1.100ft.But the new car is going to have 33x15s on it and I'm going to use the 456 gear in it.The old car weighed 3500 lbs.The car we hope it will be around 3000lbs.Hope this helps.

Jon ,it's going to depend on your convertor and how many RPM's you want to turn in the 1/4. I've got a 4.56 with a 32 tall tire in the Tbird. With a 9" spragless I was in good shape in the 1/4 at 7000 , but with a 8" it wouldn't make it under 7700. You can usually figure an extra 800 RPM over your 1/8 mile RPM from what I've seen.

Mine only changes three to four hundred.

When you are as slow as Dan it has plenty of time to change.

5:14 gear for 1/8 ,the more gear the more torque you are putting to them axles as long as you don't go over your peak hp band to much , mph will not make up for the quicker short times.

I have a couple sets of 5.83's and some 5.67's if you wish to turn it like a small block you are welcome to do so..... I would put 4.56 in it myself, on my car I found absolutely no difference between the 4.30's and the 4.56.... just loaded the engine and let the torque work.....



Randy

For the record mine in the 1/8th is a few hundredths quicker and a tick under 1 mph faster with the 4.86 as opposed to the 4.57. Biggest deal is the car reacts slower.........nearly .080 with the taller gear. We are still .400 5.80 index racing this year as they are having it again for 2010, the 4.86 will go back in after i make one more 1/4 mile outing in Feb. when the track opens back up.

As stated the converter will play a role, mines still a tad on the tight side so thats why it likes the 4.86 gear over the 4.57.

You may need to own more than one gearset, I own 3 myself for the 69 alone, its a tuning piece just like a jet in a carb.

Some of you keep mentioning small blocks.

Ponder this. Some cars just work with a setup that everyone says will not work. I know some guys run very steep gears but last year with our nitrous sbf and 29.5's we had good luck with 3.70's not ideal but it worked. Let that 200 shot of nitrous and PTC converter in our glide work!! Best transbrake 60 ft was 1.25. 5.50 1/8 mile @ 3150lbs stock suspension. Well, really the gears were setup for this years turbo combo but it worked pretty well in our junk.

I used to bracket race a Maverick with a 302 and used 4.86's though for 1/4 mile. If I used that car purely for 1/8 mile, I would have been in the 5 somethings for gears.

the deal I see is some want to spin these BBF like small blocks .... I feel thats why I built a big ford so I could utilize the Big Toeque they build, so to make it work you use a 4.30 or 4.56 and keep the rpm's down and make it use that big stroke... if I really wanted to buzz the Piss out of one I would have put a 3.59 crank in it and buzzed the crap out of it..... and put 5.14 or 5.67 in it... but why???? after all it's a Big Block.... no need


Randy

I'd rather spin mine than lug it, I put good stuff in it for this reason..........let 'er sing.



Honestly John if your first outing is gonna be an 1/8th mile track I'd try the 5.14 first. Get a good playback tach, Autometer sells a single recording style thats like 250 bucks, get some sort of electric or air shifter deal, this way the gearchange is always the same. You can make small adjustments here and there and get an accurate result.

How much does up/down gear changes effect a converters stall & torque multiplication numbers with a bigger engine? I know with the Cleveland's lower torque numbers & a tight converter, if you didn't use enough gear it was like the car gained a bunch of weight.

The question of 1/8 vs 1/4 use is a good one. If in the quarter you are supposed to gear the car so that you cross the finish line at/around the same RPM as your shift point RPM, you should theoretically be able to do the same in a car that only sees 1/8 mile use. But would doing that really be a benefit in the 1/8? Probably really depends on how much power you have to work with in the first place.

DILLIGASDAVE wrote:

The question of 1/8 vs 1/4 use is a good one. If in the quarter you are supposed to gear the car so that you cross the finish line at/around the same RPM as your shift point RPM, you should theoretically be able to do the same in a car that only sees 1/8 mile use. But would doing that really be a benefit in the 1/8? Probably really depends on how much power you have to work with in the first place.

Well take it for what it is worth, but when I ran the 514 / C-4 with 4.56's combo in the 65 Galaxie the car ran some pretty consistant 10.20's in the 1/4 ,, I can't remember the 1/8 mile times off hand but I do know there was some gruge racing going on at the All Ford Carlisle Event which has an 1/8 mile track. I decided to put some 5.43's in it and surprise everyone......................... only one I surprised was myself........ the damn thing slowed down. It almost seemed liked it screamed right through the RPM's and the torque was not there to let the car work. Lesson learned.

combined with the c4 I could see where it would have been slower, if you had a smallblock that reved like a chainsaw it might have been a different story.

the Coug wrote:the deal I see is some want to spin these BBF like small blocks .... I feel thats why I built a big ford so I could utilize the Big Toeque they build, so to make it work you use a 4.30 or 4.56 and keep the rpm's down and make it use that big stroke... if I really wanted to buzz the Piss out of one I would have put a 3.59 crank in it and buzzed the crap out of it..... and put 5.14 or 5.67 in it... but why???? after all it's a Big Block.... no need


Randy

I think you are getting caught up in the glide vs 3 speed deal here. There is a big difference because of the amount of time you are in 1st gear. A glide car will be quicker staying closer to its peak average hp rpm #'s through out the run.

More gear multiplies torque , you can multiply torque but not hp that's built in to the combo. You figure your ft/second at 130 mph and at 135 mph and figure the difference in various 60 times and see which is more important. You are thinking torque will do the work for you but it wont that's hp's job

TravisRice wrote:.....only one I surprised was myself........ the damn thing slowed down. It almost seemed liked it screamed right through the RPM's and the torque was not there to let the car work. Lesson learned.

Did it slow down on both ends? Or did any initial improvement (say for example 60ft) get erased by losses on the other end?

Thanks guys. I'll look into a 4.56 then. I have a 5.14 I can stick in there, but I think it'll be too much for the 1/4. All we have down here is 1/4 mile tracks within decent driving distance.

Got a playback tach already so I can see what it'll do on the big end.

DILLIGASDAVE wrote:

TravisRice wrote:.....only one I surprised was myself........ the damn thing slowed down. It almost seemed liked it screamed right through the RPM's and the torque was not there to let the car work. Lesson learned.

Did it slow down on both ends? Or did any initial improvement (say for example 60ft) get erased by losses on the other end?

Dave,
The car slowed down everywhere. It had a tightish 10" 4300 converter ad really just screamed through the powerband. I would have thought that the gears and tight converter would have showed some improvement somehwere inn the 1/8 mile. I actually went over the whole car to make sure something wasn't ready to fly apart in the engine. everything checked out OK, and I put the 4.56's back in, car went right back to where I left off. I would have figured something like this with a converter change but not just a gear change to run a shorter distance.

Travis