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Is a 4.30 rear end right for me?
#104684
08/14/08 10:56 AM
08/14/08 10:56 AM
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Joined: Mar 2003
Posts: 4,929
Tri-Cities, Washington
VITC_GTX
OP
master
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OP
master
Joined: Mar 2003
Posts: 4,929
Tri-Cities, Washington
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1970 GTX, original 440/727. Has the old 284/484 purple cam. Stock compression forged pistons, ported 906's shaved 0.020", FBO ignition, Eddy intake, Holley 750 DP. I currently have a 3.55 but have very little low end power with this cam. I'm sure the torque converter is part of the problem but I plan on replacing that too. I drive the car 100% street with most of that in town. When I hit the highway I am content driving 60 mph.
So, with this motor what would you think about dropping in a 4.30 and a converter that flashes about 2800???
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Re: Is a 4.30 rear end right for me?
[Re: VITC_GTX]
#104685
08/14/08 11:03 AM
08/14/08 11:03 AM
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Anonymous
Unregistered
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Anonymous
Unregistered
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i love my 4.30's. especially with the 284/484 cam.
put a higher stall converter in it and LET ER RIP! You'll say "YEEEEEEEEEEEEEEHAAAAAAAAAAAAAAA!"
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Re: Is a 4.30 rear end right for me?
[Re: buildanother]
#104687
08/14/08 11:08 AM
08/14/08 11:08 AM
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Joined: Jan 2003
Posts: 70,126
Here
DirectSubjection
Tacohead. The First and Only
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Tacohead. The First and Only
Joined: Jan 2003
Posts: 70,126
Here
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Swap the convertor first, then see if you like the results before putting in gears.
Ride eternal, shiny and chrome
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Re: Is a 4.30 rear end right for me?
[Re: buildanother]
#104692
08/14/08 12:10 PM
08/14/08 12:10 PM
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Joined: Dec 2003
Posts: 1,400
Columbia Station, Ohio
69RTSE
pro stock
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pro stock
Joined: Dec 2003
Posts: 1,400
Columbia Station, Ohio
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Quote:
I would get a 10 inch converter in there and leave the rear alone. 
Quote:
Swap the convertor first, then see if you like the results before putting in gears.
 I have a Comp cams .507/.510 lift hydraulic cam, iron heads with big valves, TM7 intake and 750 BG carb, 3400 converter. With slicks and 4.10s in my 69 Charger I went 12.20s. With street tires (275/60-15 GY Eagle Sts) and 3.23s it went 12.80s. I really like the 3.23s now, great for cruising. Don't forget a tranny cooler with the higher stall converter.
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Re: Is a 4.30 rear end right for me?
[Re: MoparforLife]
#104697
08/14/08 01:13 PM
08/14/08 01:13 PM
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Joined: Oct 2003
Posts: 11,684
W. Kentucky
justinp61
I Live Here
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I Live Here
Joined: Oct 2003
Posts: 11,684
W. Kentucky
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Quote:
For 100% street driving you will be much happier with a 3.91 than a 4.30. 4.30 is pretty deep for a street car. 3.93 at 60 mph will spin your engine approx. 3000. 4.30 alot more than that.
My small block Dart had 3.91s in it and I went to 4.30s and saw very little difference in et, something like .06 in 60' IIRC. On the street I can tell a huge difference, I run 275/60 ET Streets. Power braking will not tell you the stall of you're converter. At a slow speed in high gear floor board it, the tach will flash to the converters stall rpm. My 9.5" 4400 will only power brake to about 2800 rpm.
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Re: Is a 4.30 rear end right for me?
[Re: AdamR]
#104702
08/14/08 03:21 PM
08/14/08 03:21 PM
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Joined: Nov 2003
Posts: 4,027
Dearborn Hts, MI
Sledge_57
master
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master
Joined: Nov 2003
Posts: 4,027
Dearborn Hts, MI
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I like my 4.30's however if I wanted to drive 60mph on the freeway I'd go back to 3.91 Mines spins 3000 at 50mph with 275-60-15 tires and a 9 1/2" PTC 4200 converter. Cruisin at 60mph ain't happening for me with the 4.30's
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker
Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: Is a 4.30 rear end right for me?
[Re: GTXKen]
#104704
08/14/08 03:44 PM
08/14/08 03:44 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
Quote:
W/a 4.30 and a 27" tire, in an ideal world with no converter slippage at highway cruise, you'd be doing 3200rpm at 60mph. Can you live with that? Make sure you make that decision before you pull the trigger. Play around with this calculator here if you need help deciding.
http://vexer.com/68rt/speed.html
useful tool,(and fun) thanks for sharing
Thats AWESOME!
What is typical converter slippage at the high end? I cant see that there is NO slippage. there has to ve some
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Re: Is a 4.30 rear end right for me?
[Re: Black_Sheep]
#104706
08/14/08 04:06 PM
08/14/08 04:06 PM
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Joined: Apr 2003
Posts: 3,968
North Riverside IL & Lowell IN
GTXKen
super gas
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super gas
Joined: Apr 2003
Posts: 3,968
North Riverside IL & Lowell IN
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Quote:
Quote:
The reason I was thinking of 4.30s over 4.10s or 3.91s is that you can find so many of them
Probably because the seller figured out that 4.30:1 was too much gear for their liking...
That sounds likely
I am running 3:55s and I couldn't imagine going to anything more than 3:91s on the street. Most of my driving is around town with some occasional highway driving.
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Re: Is a 4.30 rear end right for me?
[Re: VITC_GTX]
#104708
08/14/08 06:58 PM
08/14/08 06:58 PM
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Joined: Jan 2003
Posts: 292
Atlanta
DartGTX
enthusiast
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enthusiast
Joined: Jan 2003
Posts: 292
Atlanta
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I have 3.55's and a fairbanks 2600-2800 stall converter, this works very well with my 284/484 with "fast-bleed" lifters. It is a GREAT combo and has TONS of low end torque. 440's don't need gear, just the right combination.......... Like many others have suggested, get a good 2800 converter first. If your idle vacuum is less than 13" at idle I would also recommend fast-bleed lifters to smooth it out and ADD torque. Good luck, 
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Re: Is a 4.30 rear end right for me?
#104709
08/14/08 07:10 PM
08/14/08 07:10 PM
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Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
DaytonaTurbo
Too Many Posts
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Too Many Posts
Joined: Feb 2003
Posts: 21,318
Manitoba, Canada
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Quote:
Thats AWESOME!
What is typical converter slippage at the high end? I cant see that there is NO slippage. there has to ve some
Yeah I know, that calculator is great. I use it all the time. Best of all it was made by a moparts member, tho I can't remember his user name off hand.
I'm not 100% sure on the converter slippage issue. I think a stock converter is around 95% and aftermarkets are around 90 for a good quality unit, and low 80's for a cheapie. There's a slider bar on there for efficiency so you can experiment.
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Re: Is a 4.30 rear end right for me?
[Re: MoparforLife]
#104712
08/15/08 09:12 PM
08/15/08 09:12 PM
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Joined: Sep 2006
Posts: 3,011
Sac, CA
mopowers
master
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master
Joined: Sep 2006
Posts: 3,011
Sac, CA
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Quote:
For 100% street driving you will be much happier with a 3.91 than a 4.30. 4.30 is pretty deep for a street car. 3.91 at 60 mph will spin your engine approx. 3000. 4.30 a lot more than that.
The 4.30s would spin the engine 300 more RPM (3300)in your senario. Whether or not that is "a lot more" is up to interpretation.
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Re: Is a 4.30 rear end right for me?
[Re: mopowers]
#104713
08/15/08 10:03 PM
08/15/08 10:03 PM
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Joined: Jan 2003
Posts: 25,200
Upper Midwest
MoparforLife
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,200
Upper Midwest
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Quote:
Quote:
For 100% street driving you will be much happier with a 3.91 than a 4.30. 4.30 is pretty deep for a street car. 3.91 at 60 mph will spin your engine approx. 3000. 4.30 a lot more than that.
The 4.30s would spin the engine 300 more RPM (3300)in your senario. Whether or not that is "a lot more" is up to interpretation.
Looks good on paper. In the real world 300-500 makes a big differnce and it usually doesn't work out that way. That 4.30 to me just wouldn't be that nice to drive until you put about a 30+ inch tire on. Deepest I would go is a 3.91. Been there done that.
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Re: Is a 4.30 rear end right for me?
[Re: MoparforLife]
#104714
08/15/08 11:50 PM
08/15/08 11:50 PM
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Joined: Jan 2003
Posts: 1,374
Houston,Tx.
Lee446
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,374
Houston,Tx.
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I have run 3.55, 3.91,and 4.30 on the street and track. I think you are on the right track by getting a quality converter in the 2800-3000 range. When I bracket raced my steet car, I swapped the chunks regularly and kept good records and the 4.30's were good for only 3-4 tenths with my combo. With a lot of torque, gears are not quite as critical, but deep gears just get to be a pain in the butt for all around driving. After years of experimenting and shelling ring gears at the track, I went to a Dana with 3.54's and have been very happy ever since. My .02.
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Re: Is a 4.30 rear end right for me?
[Re: DaytonaTurbo]
#104715
08/16/08 12:14 AM
08/16/08 12:14 AM
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Joined: Mar 2007
Posts: 3,285
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,285
West Coast, USA
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Quote:
http://vexer.com/68rt/speed.html
After nearly 18 years since the day I did it, this calculator gave me flashbacks of the time I had my 3.54 geared, 4-speed at 6000 RPM in 4th with 255-65 15's all around. I remember tunnel vision closing in around 135MPH, and the tunnel kept getting smaller the faster I went.
I thought I could hold it until it hit 6500 rpm, but when it hit 6000 prm, I took my foot out of it. Self preservation got the best of me. It wasn't until I got a rice rocket in the late 90's that I broke that personal top speed record.
Wow, what a rush. I'll always believe Mopars were made to dominate the half mile, as well as, the quarter. The real fun is just begining when you pass the quarter mile mark and bang it into 4th, the front end lifts back up and your glued to the seat!
Thanks for the memories!
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Is a 4.30 rear end right for me?
#104716
08/26/08 10:24 PM
08/26/08 10:24 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
And you would be surprised at the gas milage I get. But I dont care because if I did I am in the wrong hobby.
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Re: Is a 4.30 rear end right for me?
[Re: Sledge_57]
#104717
08/26/08 10:50 PM
08/26/08 10:50 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
I like my 4.30's however if I wanted to drive 60mph on the freeway I'd go back to 3.91
Mines spins 3000 at 50mph with 275-60-15 tires and a 9 1/2" PTC 4200 converter. Cruisin at 60mph ain't happening for me with the 4.30's
i checked my 4.30s out this weekend. I can do 55 mph at 3000 rpm. but my converter stalls lower than yours- around 3200.
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Ron
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