Rear Axle Gear Ratio???

[PA-IndianRider]

Another swap meet coming up this weekend. As I continue to accumlate parts I add others to my "I need this" list.

This time around I have a few items I'd love to find.... Mooneyes aluminum front fuel tank (2 gallon) - vintage Sun gauges (blue line) but most of all I'd love to find some gears for the 9" Fxxd housing I have in my work shop.

I have seen plenty of gear sets for sale at swap meets... everthing from slightly used to brand new STILL in a box.... my problem is I have no idea what ratio to look for.

I'll be running a 383 sbc with a Comp Roller cam & valve train hooked to a 400 turbo transmission - 15 x 32 x 14" Goodyear slicks.

The drag strips around here are ALL 1/4 mile tracks.

[71Dragtruck]

I'd say 4.56

[PA-IndianRider]

Originally Posted by 71Dragtruck

I'd say 4.56

I was "guess-timating" 4.56 or 4.88..... 32" tires are pretty "tall".... some VERY LIMITED street driving planned from time to time..... but I do NOT plan to "compromise" and use a higher gear just for that.

I have driven 4.88's on the street before (way back when...) so I know it's do-able even though NOT desireable or recommended.

[swb85]

The main things you need to know when selecting gears is your approximate power level and what rpm you want to turn through the lights. With 4.56's, you'll be spinning 6200rpm (+ a few hundred rpm for converter slip) at 130mph. Those are pretty tall tires you're running, you might even be able to run 5.13's..........but without knowing how big of nuts your 383 has, it's a guessing game.

[PA-IndianRider]

Originally Posted by swb85

The main things you need to know when selecting gears is your approximate power level and what rpm you want to turn through the lights. With 4.56's, you'll be spinning 6200rpm (+ a few hundred rpm for converter slip) at 130mph. Those are pretty tall tires you're running, you might even be able to run 5.13's..........but without knowing how big of nuts your 383 has, it's a guessing game.

From what my engine builder is telling me the engine should be making about 425-450 hp..... I know at THIS POINT all of this is somewhat of a "guessing game" ..... but I got to START somewhere..... got a line on some 4.88's which could be a compromise that I could start with. Need something to fill up the "bare rearend housing" I have sitting on my workshop floor.

[swb85]

With 450hp you can run a lot of gear. At that power level you're probably gonna run ~110mph tops in the 1/4 (obviously depending on race weight). My assumption is you probably won't turn much over 6000rpm, 4.88's would put you at 5600rpm (+ converter slip) at 110mph.......just about right.

[RatPwrd72]

I vote for the 4.88's. I'm running 5.38's right now with a 468, TH-400, Transmission Specialties spragless 4000 stall, 12 bolt rear and 32x14x15 slicks. It ran 10.80's @ 121 with the old 396 (I haven't ran the 468 yet in the 1/4). We're switching back to 4.88's to lose some RPM (Going through the lights @ 7100). Also, it "hits" the tires really hard off the line.

With the 4.88's, you'll have room to "grow" with more HP. If you over gear now, you'll have to buy another set later on....

[Super73]

Just food for thought..

Last time at the track the truck weighed 3,900 with me in it and a half tank of gas.
I run a 30" tall tire.
I make 430rwhp naturally aspirated with the converter locked (roughly 390rwhp unlocked)

With 3.73's on a 30" I was turning 7,400 RPM in second gear through the traps at 112mph. This is with a 4L80E which has the same gearing as a TH400.. Second gear is a 1.48 ratio.

Here is a link to a spreadsheet I made for gearing. Most likely it will help you quite a bit. For converter slip, keep 15% in for the time being unless you know for sure what it is slipping. I know my 4,400 verter has 9% slip on the upper side of things.

http://73-ls1.com/misc/gearing_revision_2.xls


I'm going to 4.56's with the 30" tire but planing on doing low 130's on the bottle and spinning to 7,400 rpm.

[nxtruck]

Is there any chance that you'll be using nitrous at any time? This will change your gearing needs. If you don't plan on any spray, a 4.56 or 4.88 would get you close, as the rest of the guys have already said. If you would decide to spray that 383 at some point, you'll end up needing something along the lines of a 4.10 or a 4.33. There again, all of this depends on how high you plan on spinning the motor. A lot of variables come into play here.

[Super73]

If you are planing on spraying, I have a set of motive 4.10's for a 9" laying around..

[PA-IndianRider]

Originally Posted by Super73

If you are planing on spraying, I have a set of motive 4.10's for a 9" laying around..

No juice for this "Milner".... too old school for nitrous.... at least that's what I'm saying NOW!! Planning to setup & go ALL motor.... I'd be more than happy to run the times stated above.

Forgot to mention before I also have a 3800 convertor & going to have the turbo 400 I picked up opened up, looked at, checked & rebuild as needed... and while it's apart going to have a trans brake installed.

As for "race weight" I will be cutting out everything I can and what I can't I will TRY to replace with lighter material/parts. Already have the fiberglass one piece frontend, rear fenders, straight front axle, no heater/defroster/inner fenderwells, radio, aluminum floor & chopped top.

[71Dragtruck]

Originally Posted by PA-IndianRider

No juice for this "Milner".... too old school for nitrous.... at least that's what I'm saying NOW!! Planning to setup & go ALL motor.... I'd be more than happy to run the times stated above.

Forgot to mention before I also have a 3800 convertor & going to have the turbo 400 I picked up opened up, looked at, checked & rebuild as needed... and while it's apart going to have a trans brake installed.

As for "race weight" I will be cutting out everything I can and what I can't I will TRY to replace with lighter material/parts. Already have the fiberglass one piece frontend, rear fenders, straight front axle, no heater/defroster/inner fenderwells, radio, aluminum floor & chopped top.

N2O is old school, they used it in fighter planes during WWII.
I noticed a couple of weeks ago when I picked up a new bottle that NOS systems went retro on thier new bottles to the old bottle and lable colors so it will fit right in on your setup, go ahead pull the trigger.

[PA-IndianRider]

Originally Posted by 71Dragtruck

N2O is old school, they used it in fighter planes during WWII.:

HA!!! ...... and they also used to use it when pullin' TEETH ....

[Marv D]

I know you mentioned it before, but what heads are you going to use???? 450 at the crank is really not that much motor these days.

[PA-IndianRider]

Originally Posted by Marv D

I know you mentioned it before, but what heads are you going to use???? 450 at the crank is really not that much motor these days.

The heads will be aluminum that are reworked by the shop that is building the engine. Not sure of ALL of the specs of the heads but they will be built beyond the 2.02's Next time I talk to my builder I'll find out.

Yes.... I do know the HP of the engine is LOW by today's standards. W o W ... what used to be unheard of years ago is so obtainable today.

Yes, I have had thoughts of building a stronger engine... even had some daydreams of going BIG BLOCK.

Hanging out on this forum definately has me re-thinking the GOALS/PLANS I have made for my engine build. Even though it is some time off in the future my wheels are already turning about what to do about the horsepower level I am shooting for NOW.

You guys are the EXPERTS.... what would you build ????.... on a BUDGET that is !!!!

I cannot afford to build a "maxed out" small block.... afterall this C10 is NOT intended to be a serious ALL-OUT drag racer. Still plan to do "some" limited street use (shows, cruises, etc)

I saw a small SBC at the machine shop that was built for one of the owners street rod - bored/stroked 427 sbc ..... awesome ..... but so is the $$$ PRICE $$$ to builld an engine like that.

The engine I have planned to built (4 bolt mains) is going to have MORE done to it than any engine I have had in the past.... stroked - balanced - .030 bore - re-worked aluminum heads - roller cam & rocker arms - Edelbrock Performer RPM Air gap - 750 Holley carb - pump gas motor.

So any suggestions would be appreciated.... still have a LOT of time before I take the block to the shop..... "still have a LOT of time to change my mind".

[bigjimzlll]

I have a set of Richmond 4.86's I don't need. PM me

[Super73]

I can find 5.3 LS1's all day long for under $800. This is from Throttle body to oil pan. Fuel injectors all the covers. The 5.3 is an Iron motor, but they come with pretty decent alum heads right out of the box. Ditch the intake, do a crank pulley, headers, port the throttle body and stick the righ cam in it and your at 450hp.. This all can be done for less than $2k..

You can find 6.0's fairly cheap too these days. You could warm one over pretty well for sub 3k and be making about what I make to the wheels. It won't fe a forged motor, but it would go pretty darn good..

[whatnow123]

BTW, I don't know if I would ever purchase a used gear set. I bought a used rear, the gears looked okay but they whined so bad you couldn't hear yourself think over 50mph. Having set up a few of these, I can see how some would get frustrated and stop at "close enough" and then wonder why they whine, mess up the mesh and sell them as slightly used. If it's drag only, no problem but if you are going to drive it at all on the street, buy new and make sure they are set up correctly.

[PA-IndianRider]

Originally Posted by whatnow123

BTW, I don't know if I would ever purchase a used gear set......

I agree and normallyI also feel the SAME way about buying CERTAIN used parts.

But in this case BIGJIM is someone who I feel I know & can TRUST because he is NOT ONLY a frequent participant on this forum but also a "moderator".

Little by little the bunch of guys that "hang-out" on the racing-high performance forum on this website have formed a pretty solid group of drag racers from which experiences, advice, high & lows and also parts are shared.

If you like to "burn up the 1/4 mile" ..... join us!!!!