Opinions on 3.89 gears or ??

[winr1]

29" tall rear tires .. 3.89 gears
MPH         RPM
30-------- 1388
40-------- 1851
50-------- 2314
60-------- 2777
65-------- 3008
70-------- 3239

I think this is the ratio gonna put in my 65 F100
Not gonna go far from home, cruise ins an car shows , puttin around
Cant seem to make a decision anymore bein old an such

It is 200 lbs lighter at the moment, gonna remove another 3 or 400

Tube cross member with engine mounts, F1 front axle with coilovers

1 x I-beam with spindle is 5 lbs lighter than the F1 axle with both spindles

The factory crossmember, I-beams, coil springs, radius rods are real heavy

Alum. radiator, bedsides only, tailgate will be a shell, mustang tank in rear

Building a light weight bench seat around 30 lbs lighter than factory

DeWayne gave me a C4 pan fill case so I can swap the innards out of my C4 case fill

Will fit JPT bell I have an save around 30 lbs


Thoughts ??



Ricky.

[Thumperbird]

What's the engine combo./hp behind this and expected low end torque?
Rear tire width?

[Falcon67]

I run 4.56 and a spool with 28" tires - all depends on what you want.  If you are just showing, cruising and using a 11" performance converter that stalls in the 2000~2200 range, then 3.50~3.70 would be a good balance.  Those RPMs are theoretical anyway because of converter slip/lockup, actual tire diameter under load, etc.

[BattlestarGalactic]

I run 3.89 in my black car with 275/60/15 BFG radial TA's.  Nice all around gear.  Approx 3000 rpm at 65 mph.
I do run 4.56 in my pickup with 29" tires.  It spins the old 428 pretty hard on the highway, but it doesn't seem to care.  Approx 3500 rpm at 65 mph.

Neither have accurate speedometers, so it's just a close guess running with traffic.

[cjshaker]

I run 3.89 in my black car with 275/60/15 BFG radial TA's.  Nice all around gear.  Approx 3000 rpm at 65 mph.

Same here. I ran that combo in my Mustang for years. A good compromise between performance and streetability. That was with a stock stroke 427 though. If it was a big stroker engine with lots 'o torque, something in the 3.70 range would probably work good.

[winr1]

Sorry... should of added mill/trans heh 

.040 390/428 crank// D2 heads/ bowl port/CJ valves.. ported Performer intake

Also have Ed. 2x4 and Ed. old style 3x2 intake

C4 or C6 with 10" or 11"  convertor .. 2200 or so stall

Rear tires are 255/70/15... not real wide 



Ricky.

[Falcon67]

10" is going to be way more than "2200" - more like 3K plus. 11" is usually in the 2200~2500 area.  The thing to watch for is when "cruising RPM" is below converter lockup, that's when you can be building heat in the trans due to slippage. 

[plovett]

10" is going to be way more than "2200" - more like 3K plus. 11" is usually in the 2200~2500 area.  The thing to watch for is when "cruising RPM" is below converter lockup, that's when you can be building heat in the trans due to slippage.

That is true, but remember that a converter doesn't have a set lock-up rpm.   It depends on the load.  At high rpm (power) and high load, it will stall higher.  At lower rpm and lower load it will stall lower.   What  I am getting at is that it is possible to cruise under the rated stall speed without any problem.   If the throttle is barely open and you are not accelerating, the converter will slip less. 

Torque converters are an amazing device.   They can multiply torque under high load and reduce stress on the drivetrain while maintaining similar cruise conditions.  They are certainly less efficient in terms of power transfer and mpg. 

JMO,

paulie

[plovett]

What cam do you have in there?

paulie

[Thumperbird]

Having just gone through this, 2 cents worth here:

Depending on cam, with those narrow tires, I see no need to get too crazy with gearing or stall for that matter, no way to hook it up and you would be moderate rpm's on the highway.
Broader did a 2600 rpm 12" for me, like it a lot better than the 3200 10" I originally had, just feels right in the heavy Thunderbird at low rpm's.
Unless your fun is smoking tires which I understand can be, then seems like 3.5 to 3.7ish is enough.

For the street I look at it like this, from a brake, if full throttle launch spins them immediately thru to 2nd then no need for more gear or stall correct?
Of course there is that bug for quick and fast which will have you looking at your suspension and tires soon enough anyways so I change my mind, gear it up.

[plovett]

For the street I look at it like this, from a brake, if full throttle launch spins them immediately thru to 2nd then no need for more gear or stall correct?
Of course there is that bug for quick and fast which will have you looking at your suspension and tires soon enough anyways so I change my mind, gear it up.

This is true.  However, if more traction is in store in the future then maybe lower gears might be good.   

My Cougar spins the tires up to about 65-70 mph on 10" street radials and maybe 30-35 mph on cheater slicks, on street surfaces.  So you might think I need less gear and less stall, and that WOULD help, but even better would be me getting my suspension in order so I have the benefit of traction AND gearing. 

I have 4.11 gears with 3600 stall and 27" tall tires in a lighter vehicle with a bigger engine (I think) so different, yet same situation.  aaaahhhhhhhh, very wise, grasshopper.   Not saying I am wise, just making a "Kung Fu" reference.

JMO,

paulie

[winr1]

No cam yet...


Ricky.

[plovett]

Well, gearing, cam, stall speed, vehicle weight,  rpm range, all must match, for the best result.   The cam is a major component that affects all your other choices and vice versa.

So....what are you thinking for a cam?

JMO,

paulie

[e philpott]

my take is gearing is it's not as important as the Cam and Converter matching each other is . The  last project 71 Mustang I did the drivetrain on I finished the vehicle before his Moser ( complete 9 inch conversion 3.50 ) was shipped so we tested the manual shift Broader valve body C-4 transmission 3K stall on the 1971 429 clone, Aluminum CJ heads , Comp 294S Cam with the cars original 302 8 inch  2.75 gear axle and that Cam and Converter was fine and influenced the final decision on 3.50 gears from initially wanting 4.11 and he almost went with the 3.00 to 1 after driving the 2.75 gear , it drove that nice in town and was great on the highway with some MT 275-60-15 street drag radials and 2.75 gear

[Falcon67]

That is true, but remember that a converter doesn't have a set lock-up rpm.   It depends on the load.  At high rpm (power) and high load, it will stall higher.  At lower rpm and lower load it will stall lower.   What  I am getting at is that it is possible to cruise under the rated stall speed without any problem.   If the throttle is barely open and you are not accelerating, the converter will slip less. 
...
JMO,

paulie

Depends on the converter and how "loose" it's designed.  Most off the shelf "Saturday Night Special" 10"s will error on the tight side -at least in my experience.  The 10" 3800~4000 I had built for the 302 is not that and will get the trans to around 200F in maybe 20 minutes of very light throttle cruising.  But it's yank the front tires on the track - which is what I want, as opposed to driving around a lot.

For the street I look at it like this, from a brake, if full throttle launch spins them immediately thru to 2nd then no need for more gear or stall correct?
Of course there is that bug for quick and fast which will have you looking at your suspension and tires soon enough anyways so I change my mind, gear it up.

Sorry - this makes no sense at all.  The converter does not control the shift points - unless you have a manual valve body, those will be determined by the valve body programming and the governor.   If the converter is way loose, then I think that may be what you are saying - RPMs will "wing" and the trans will shift at whatever RPM it is set for.

[Thumperbird]

"Sorry - this makes no sense at all.  The converter does not control the shift points - unless you have a manual valve body, those will be determined by the valve body programming and the governor.   If the converter is way loose, then I think that may be what you are saying - RPMs will "wing" and the trans will shift at whatever RPM it is set for."

Communication breakdown...
All I was trying to say was why run more gear and higher stall if just a street car and low rpm launch still spins tires significantly into 2nd gear.  Followed by if you get a bug for speed and you have plenty of hp/torque then you may want to reconsider if suspension and tire upgrades are in the future.

[cammerfe]

When I ordered my '64 Custom/427, I had a choice of a 4.11 or a 3.50. So I ordered the 4.11. I soon found out that the 4.11 was just fine for running around town, but I needed a 3.50 for highway cruising. I put a set of 8.20X15 tires on the rear, and made a little chart that I taped to the dash. 3000 was about 70 in 4th gear.

The nice thing about the 3.50 was that I could shift back into 3rd at 100 and have a serious passing gear---or just the thing for dealing with 'vettes and 409 chibrolays on the highways. And with the 3.50, 2nd gear was just great for roll-racing around home. Higher-numerical-geared cars were wanting to be in 3rd but I had very usable RPMs left to enable me to get a jump.

I had a top speed of over 150 with the highway combo, but the steering got very light starting at about 130. (The speedo only went to 120, but the needle would show in the 'gen' red light next to the 120 line on the dash.)

KS

KS

[plovett]

When I ordered my '64 Custom/427, I had a choice of a 4.11 or a 3.50. So I ordered the 4.11. I soon found out that the 4.11 was just fine for running around town, but I needed a 3.50 for highway cruising. I put a set of 8.20X15 tires on the rear, and made a little chart that I taped to the dash. 3000 was about 70 in 4th gear.

The nice thing about the 3.50 was that I could shift back into 3rd at 100 and have a serious passing gear---or just the thing for dealing with 'vettes and 409 chibrolays on the highways. And with the 3.50, 2nd gear was just great for roll-racing around home. Higher-numerical-geared cars were wanting to be in 3rd but I had very usable RPMs left to enable me to get a jump.

I had a top speed of over 150 with the highway combo, but the steering got very light starting at about 130. (The speedo only went to 120, but the needle would show in the 'gen' red light next to the 120 line on the dash.)

KS

KS

Well, if you hit 150 mph, then it sounds like you were running about 6500 rpm.  That sounds very plausible to me, and fun.   

I had a Porsche 914 once (I know, weak), but it would go 120 mph.  It was the 2 liter version.  The front end felt like it was off the ground at that speed.   It needed an air dam SO bad. 

I had my '66 Fairlane GTA (with a 428CJ) up to 145 mph and it felt much more stable.

paulie

[plovett]

double post. sorry

[machoneman]

double post. sorry

I can tell you that my '70 Stang (and '69's as well) does get light in the front at over 130 or so. I know, others here have not had this happen but my SBF with a a lot of light weight parts (heads, intake, pump, P/S delete and much more lightening) does get scary light. It's the shark-nosed front end with the taper facing the wrong way (pushes up) that even with the factory air dam gets way too much air under the front. A SCCA pal noted that others (all light weight fronts w/SBF power ) have had similar issues, some at nearing 145-150. A clue is the massive front air dams Ford used in the famed '69-'70 Trans-Am series where the bottom of the dam nearly touched the ground (think: Bud Moore prepped cars). That under-the-chin "lift spoiler" was big for a reason!

[Falcon67]

"Sorry - this makes no sense at all.  The converter does not control the shift points - unless you have a manual valve body, those will be determined by the valve body programming and the governor.   If the converter is way loose, then I think that may be what you are saying - RPMs will "wing" and the trans will shift at whatever RPM it is set for."

Communication breakdown...
All I was trying to say was why run more gear and higher stall if just a street car and low rpm launch still spins tires significantly into 2nd gear.  Followed by if you get a bug for speed and you have plenty of hp/torque then you may want to reconsider if suspension and tire upgrades are in the future.

Well said - sorry for the miss-communication.

[cammerfe]

double post. sorry

I can tell you that my '70 Stang (and '69's as well) does get light in the front at over 130 or so. I know, others here have not had this happen but my SBF with a a lot of light weight parts (heads, intake, pump, P/S delete and much more lightening) does get scary light. It's the shark-nosed front end with the taper facing the wrong way (pushes up) that even with the factory air dam gets way too much air under the front. A SCCA pal noted that others (all light weight fronts w/SBF power ) have had similar issues, some at nearing 145-150. A clue is the massive front air dams Ford used in the famed '69-'70 Trans-Am series where the bottom of the dam nearly touched the ground (think: Bud Moore prepped cars). That under-the-chin "lift spoiler" was big for a reason!

One thing I didn't mention before was that I used spring jacks in the front coils (the kind that you put between the turns and then screw apart to open the spacing). The idea was to get a bit of 'squat' in the back to help weight transfer. With Traction Master bars in the back and 8" M&H Dragsters on it, the traction was pretty good, but it let the air get under the front quite easily.

I was dating a girl who lived in a North Western suburb of Detroit, who was going to Michigan State in East Lansing. Her Dad would get her on Friday night, but I'd drive her back Sunday evening. I was coming home about midnight, one Sunday night, running on I-96, with nobody around. Then I saw headlights behind me. I was doing about 75, and he was doing about 80. When he got even, I saw it was a 'Vette, and as he started to go past, I nudged it up to about 85. and then he... At about 100, and even up, I made an emphatic downshift to third and stomped it. I wound it out before shifting back to fourth. I'd pulled him pretty good, but he didn't quit, so I stayed in it. As I said above, the speedo needle would show in the red 'gen' light, probably at about 130-135. I did take it to about 6500 before I quit, and he was just little lights in the distance behind me. But I was steering with only one finger and thumb on each hand so as to not put too much emphasis on the steering wheel. Luckily, the E-way was straight in that area because the wheel was giving almost NO input. Hopefully, I'm a bit smarter by this time.

Getting ready for ECTA with my Lincoln LS, I found that the top speed was also over 150, but that the best I could do in one mile from a dead stop, was 140.106. And that was with the help of a competition kit from NX, who sponsor me, and using methanol with the spray instead of gasoline. The kit was sized to give 400 HP+ with gasoline but I only had nominal 'pills' in it for 100, and I didn't turn it on until I went into third gear, to save the trans internals. That set the record, which I hold to this day.

KS

[AlanCasida]

If I wasn't planning on taking it to the track I'd put a 3.25 gear in it and enjoy cruising in it...but that's just me. 

[My427stang]

I like the idea of the 3.89 with the 29 inch tall tire.  Does the engine have the oats to let it rev a little when you want to play?

3.89 sounds a little deep, but it isn't far off a car with 245/60s and a 3.50 gear.  All depends on the build, if real stock, I might go for the calm behavior of less gear, but if it's a little ornery, go for it    

[machoneman]

I like the idea of the 3.89 with the 29 inch tall tire.  Does the engine have the oats to let it rev a little when you want to play?

3.89 sounds a little deep, but it isn't far off a car with 245/60s and a 3.50 gear.  All depends on the build, if real stock, I might go for the calm behavior of less gear, but if it's a little ornery, go for it

I like the 3.89's as well but note that a lot depends on your driving experience. If in a rural area and/or with lots of highway driving, it's a lot of rpms. But if it's limited highway and lots of stop and go driving (say, in urban areas) they should work great.

[winr1]

Thanks for all the replys guys 

My Friend who builds 9" 3rd members is sellin me a nice used 3.50 ring an pinion for $50.00

As said above, I can go to some shorter/wider rear tires to change the ratio up a bit

Now to decide between a 4 speed or auto..... lol ..



Ricky.