Which 8 3/4 rearend gearing for the street? You decide.

[tsteiner61]

The vehicle: 1973 Dodge B100 1/2 ton van
The setup: 318 9.0 compression, .480/.480 cam, 600 cfm Holley, 2800 stall converter on 727, lowered front and rear 2-3", total vehicle weight 4000 lbs. (truck scales actual weight). -489 8 3/4 rear.
Driver's preferences: Daily driver vehicle, more interested in performance than gas mileage. May take to strip, but not very often, just for fun.

[rumblefish360]

Whats the duration of the cam? Advertised and @ .050 if you please. Also, what size tire is being used?

[tsteiner61]

The tires will be BF Goodrich Radial T/A
295/50R15.


This is the cam I am planning to get. It is a hydraulic roller retrofit style.

COMPETITION CAMS CAMSHAFT SPECIFICATION SHEET

PART # 20-608-8
GRIND NUMBER: CRS254HR-12
ENGINE: CHRY SML BLK 273-360
INTAKE EXHAUST
VALVE ADJUSTMENT HYD HYD
GROSS VALVE LIFT .480 .480
.006 TAPPET LIFT 254 262
VALVE TIMING OPEN CLOSE
AT .006 INT 19 BTDC 55 ABDC
EXH 67 BBDC 15 ATDC
THESE SPECS ARE FOR CAM INSTALLED
AT 108 INTAKE CENTER LINE
INTAKE EXHAUST
DURATION AT .050 199 206
LOBE LIFT .3000 .3000
LOBE SEPARATION 112

[68Charger 440HP]

I think you sould go with 3.55's. This gear will give you a good mix between performance and streetability. I run 3.55's and at 3000rpm I am going 65mph with the same tires you have. The 3.91's will put you at 55mph at 3000rpm. 3.55's are a great duel purpose gear. Good luck.

Clayton

[Speedy#1]

i was talking to the guy from DTS at the auto rama in Det and he said to use a 3;55 becaure you can use three diffrent size tires to change the gear ratio.smaller tires 3;91 larger tires 3;23 .I run a 15'tire on the street and a 14' tire on the track the bolt patern is the same on a 81/4 . I would rather change tires than gears.

[PLUM CRZY]

I had this same issue last year. I was getting all kinds of advice. I chose the 3.91. This gear is WAY fun!!! I just drive the car for fun, not everyday transportation, so the occasional 70mph blast down the expressway with the high RPM doesnt bother me. If you go to www.randysringandpinion.com they have some gear/rpm calculators that might help your decision. This is where I bought my gear. Had a good experience with them, no problems at all.

[Fury Boy]

I think that 3.73s w/ 28 in tires are the ultimate st up for almost any car. You could always get 26 in slicks to run at the drags so you might have close to 3.91s

[rumblefish360]

Hey Furyboy;

When was the last time you have seen a 3.73 set up for a Chrysler? I would do a 27 inch tire MAX! 26 would be better!

[tsteiner61]

Thanks for the advice all. 3.91:1 is the winner (see poll results). I'll be ordering mine next week!

[mshelly]

I run them w/28" tires, and the combo is just right for me.

Be careful if you choose U.S. Gear, unless you don't mind some noise!

They admitted to me that they whine (after the purchase) and won't take them back if you are dissatisfied. Something about low production runs don't make proper machine setups and QC economical. 3.91:1 for a 489.

What is this... U.S. Gear or China Gear? It's not like they are making $9.95 bench vices!

Thanks, had to get that off my chest again.

[powerwagon]

I have 3.55 (maybe 3.54?) in my 78 pw, with stock 360. If you have a small block, you don't have as much torque as a big block, so you better go with lower gears to make up for it. My truck only gets 7 on the highway, but that is because it is full time 4wd. Now in my challenger i am working on, i will run abourt 550 horse 440, so i will probably run 3.23's or less because i have the torque to make up for higher gears, that way i can retain a little of my gas mileage. my 2 cents worth

[JCFcuda]

I ran a 340 cuda w/4.10 great around town, Hated to take it on the highway you really have to turn the radio up to hear it.
Jim

[1969RR]

What do you guys think of running 4:30 with 30 inch (275/70R-15 or 285/70R-15) tires around town? This way I can change over to 26 inch slicks for the track and get the full potential by just changing the tire size.

[72Challenger]

A 26 inch tire with 4.30's is the same as a 30 inch tire with 3.73's. Still maybe a little high for the street, but definitely easier than swapping pumpkins, and way cheaper than an overdrive unit. BTW, why do so many people recommend 3.73's for Mopars? They aren't made!


------------------------------------------------

Oops! Please note this correction. The above comparison is backwards. Using the 30 inch tires with a 4.3 would be the same as having 26" tires with a 3.73

[1969RR]

275/70R-15's (30.15 dia) would put me at 2880 rpm at 60mph. My 3.23 which are in it now at 60mph put me at 2500 (with my current 235/60R-15's). Thats only a 300 - 400 rpm change and it seems like I'm getting more in return and also options. Don't you think?

[NitroMethane]

Actually, Randy's Ring & Pinion makes 'em. Saw them in a 4x4 magazine.