I'm installing my new motor starting this weekend, and it got me thinking about going to bigger rear gears for my next mod. The car will be a steet/strip car. The motor is 525hp 383ci built by AR Racing. It makes it's power in the 2500-6500rpm range, has a Team G sinlge plane intake, and pretty large roller cam with .525"+ lift (can't remember all the specs off the top of my head). I have a 4 speed right now and 3.36 gears. This combo didn't launch the car that great with my old motor which had a Comp Cams 268XE cam in it, so I'm sure it won't be any better with the new motor. I'm looking into something from Richmond Gears. Specifically the 3.70, 3.90, and 4.11. I rarely drive the car on the highway since even with the 3.36's the car is revving around 3,000 at 70mph. I also plan on going to a Richmond 6 speed with the .62 overdrive and 2.77 first gear sometime next year, and then I'll drive it occasionally on the highway. Will the 4.11's and 2.77 first gear be too much off the line for the tires? I forgot to add that I'l also be getting 17x9.5" wheels on the rear with 275 BFG G-force T/A's. With the 4.11's and the 6 speed I can cruise on the highway and only be doing 2300@70mph. What do you guys think :confused: . I'm also gonna try the Richmond tech line and see what they say also. Thanks in advance :cheers:


[Modified by Ryan77, 5:24 PM 1/1/2004]

 

Ryan,
I just put 355's in my 74 with a 2004r overdrive trans. I haven't driven it much but I know it turns 1800 at 60mph. If I had to do it over again I would go with the 373's. 410's should be ok with an overdrive unit.

 

Thanks, I think the 4.11's should be fine with the 6 speed too :cheers:

 

Speed vs. RPM For Tire and Gear Ratio http://smokemup.com/auto_math/mph_range2.php

Do a little plug-n-chug with one of the many online gear ratio calculators to see what suits you.

I've heard that Dragstrip 2000 (sp?) is good software for deciding what the most effective gear combination is...

 

Ryan:
I put 3.73s in my '82 (with the stock 700R4) in October; I turn 2000 @ 60 MPH. At the strip, I trapped @ 90.89 MPH, going 4300 in 3rd gear. If I had it to do-over, I'da got the series-4 carrier, and gone with 4.11s, maybe even 4.56s! I'd like to trap closer to 5000 RPM; if I mod the Cross-Fire in ANY way, I'll almost HAVE to trap at a higher RPM.

my74ls4:
I seriously doubt you'll hook all that power-up, with 4.11s and a 2.77 First Gear. I had approx 425 HP/TQ in my old '79 Z28, and had a 2.75:1 low-gear THM400, 4.11s, and 'stickie-street' 26" x 8" tires. with a 'tight' 10" converter, it'd hook (barely), but with an 8"/4500 stall converter, it blazed the street tires.
Can you get a 'taller' 1st gear for you as-yet un-bought transmission? It seems you almost have TOO-MUCH a spread (2.77-to-.6 OD) to 'use' all that power...
Just my $.02 worth.....

 

Mike, I played with all the calulators on the Richmond website. That's where the 2300rpm@70mph came from. I haven't played with the drag strip calculator yet though.


Glen, I think I am going with the 4.11's and the 4 series carrier. Somewhere down the road I'll upgrade the rest of the rearend with parts from Tom's Diff's, maybe even one of their independent 12 bolt setups if I get involved enough in drag racing so I can run some slicks to hookup all that power. As far as the tranny, the 2.77 1st tranny has the best split of gears, the others all have bigger first gears, they go all the way up to a 3.28 1st gear. Here's a link to them:

http://www.jegs.com/cgi-bin/ncommerc...43&prmenbr=361
The one I plan to get is second from the bottom :cheers:



[Modified by Ryan77, 4:36 PM 1/2/2004]

 

Ryan:
500+ ft/lb of TQ, 2.77:1 First Gear, and 4.11 rear gears, on street tires?
:skep:
I think I'll buy more stock based outta Akron, Ohio (Goodyear).
:lol:
I run OEM-sized (255/60R15) BFG TA Radials on the OEM (8" wide N90) wheels under my bone-stock '82 Cross-Fire (quit laughing!!!), backed by the 700R4's 3.06:1 First Gear, and a set of 3.73 rear gears. EVEN my 200 HP result in wild tire-spin!
I suspect you'll have MORE problems than I, but 'rowing-your-own' & 4.11s will be a blast!!!
:thumbs: :chevy :thumbs: :chevy :thumbs: :chevy :thumbs: