Moparts
Is a 4.30 rear end right for me?
Posted By: VITC_GTX
Is a 4.30 rear end right for me? - 08/14/08 02:56 PM
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???
Posted By: Anonymous
Re: Is a 4.30 rear end right for me? - 08/14/08 03:03 PM
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!"
Posted By: buildanother
Re: Is a 4.30 rear end right for me? - 08/14/08 03:05 PM
I would get a 10 inch converter in there and leave the rear alone.
Posted By: DirectSubjection
Re: Is a 4.30 rear end right for me? - 08/14/08 03:08 PM
Swap the convertor first, then see if you like the results before putting in gears.
Posted By: GoodysGotaCuda
Re: Is a 4.30 rear end right for me? - 08/14/08 03:09 PM
Just making sure. You haven't had a converter built around the 3.55s and are going to 4.30s, right? You will be getting the converter tailored to 4.30s?
Posted By: VITC_GTX
Re: Is a 4.30 rear end right for me? - 08/14/08 03:23 PM
The converter in there now was supposed to be the 340 converter. I don't think that's what I got though. Others around here that are using them have a lot better luck than I do. I will be getting a new converter, something very street friendly.
I did pony up the cash for a PTC from Kenny for the Demon (3600 flash) and it's great on the track, drivable on the street but I think one like that is a little to much for this car. Thinking maybe ~2800-3000ish??
Posted By: Jeff_383
Re: Is a 4.30 rear end right for me? - 08/14/08 03:29 PM
What does the coverter flash to now, and how was the that cam installed? Advanced, straight up?
Posted By: MoparforLife
Re: Is a 4.30 rear end right for me? - 08/14/08 03:56 PM
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.
Posted By: 69RTSE
Re: Is a 4.30 rear end right for me? - 08/14/08 04:10 PM
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I would get a 10 inch converter in there and leave the rear alone.
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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.
Posted By: Grassosgarage
Re: Is a 4.30 rear end right for me? - 08/14/08 04:23 PM
4.30 + 275/75/15 tire + your 440 combo =
Posted By: VITC_GTX
Re: Is a 4.30 rear end right for me? - 08/14/08 04:40 PM
Right now I have 275/60-15 with 3.55's. I'm guessing my converter hooks up at 2000-2200ish. My tach isn't accurate (electronic ignition).
I know this isn't the best indication but when I power brake the car it breaks loose at about 2000-2100.
Posted By: VITC_GTX
Re: Is a 4.30 rear end right for me? - 08/14/08 04:45 PM
The reason I was thinking of 4.30s over 4.10s or 3.91s is that you can find so many of them. I had a really hard time finding a 3.91 for my Demon. And 4.10s seem impossible to find.
Posted By: nutso suave
Re: Is a 4.30 rear end right for me? - 08/14/08 04:46 PM
go with a 4000 stall converter. 3:55s are great on the street.
Posted By: justinp61
Re: Is a 4.30 rear end right for me? - 08/14/08 05:13 PM
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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.
Posted By: DaytonaTurbo
Re: Is a 4.30 rear end right for me? - 08/14/08 05:36 PM
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
Posted By: nutso suave
Re: Is a 4.30 rear end right for me? - 08/14/08 05:39 PM
daytona-
i love that thing! it is very useful to pick your 4speed ratios too. very cool!
Posted By: AdamR
Re: Is a 4.30 rear end right for me? - 08/14/08 07:11 PM
I would do the converter first. Have it made for the car not what you think it need.
Posted By: bobby66
Re: Is a 4.30 rear end right for me? - 08/14/08 07:17 PM
A convertor for 3.55s may not be what you need for 4.30s.
Posted By: Sledge_57
Re: Is a 4.30 rear end right for me? - 08/14/08 07:21 PM
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
Posted By: GTXKen
Re: Is a 4.30 rear end right for me? - 08/14/08 07:24 PM
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
Posted By: Anonymous
Re: Is a 4.30 rear end right for me? - 08/14/08 07:44 PM
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
Posted By: Black_Sheep
Re: Is a 4.30 rear end right for me? - 08/14/08 08:02 PM
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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...
Posted By: GTXKen
Re: Is a 4.30 rear end right for me? - 08/14/08 08:06 PM
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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.
Posted By: 68Bullit
Re: Is a 4.30 rear end right for me? - 08/14/08 09:09 PM
After I sell my 3.91's, I'll be going with 4.30's
Posted By: DartGTX
Re: Is a 4.30 rear end right for me? - 08/14/08 10:58 PM
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,
~1.JPG "4619335-GTX(7)~1.JPG")
Posted By: DaytonaTurbo
Re: Is a 4.30 rear end right for me? - 08/14/08 11:10 PM
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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.
Posted By: Kudakidd
Re: Is a 4.30 rear end right for me? - 08/14/08 11:53 PM
4.30's? Hope you have a gas tanker truck following you around!
Posted By: 383man
Re: Is a 4.30 rear end right for me? - 08/15/08 09:44 PM
I run 4.30's in my 63 with my mild 440 and I love them. But I use a 29" tire as I wanted a fairly tall tire to fill the wheelwell. I drive it on the highway at 60 mph all the time and it tach's between 3000 to 3200 running 55 to 60 mph. I wanted the gear to still give me a good launch with the 29" tires. And I love it as I just drive at 60 mph on the highway and still have a great launch when I get to the track. 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.
Ron
Posted By: mopowers
Re: Is a 4.30 rear end right for me? - 08/16/08 01:12 AM
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.
Posted By: MoparforLife
Re: Is a 4.30 rear end right for me? - 08/16/08 02:03 AM
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.
Posted By: Lee446
Re: Is a 4.30 rear end right for me? - 08/16/08 03:50 AM
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.
Posted By: jbc426
Re: Is a 4.30 rear end right for me? - 08/16/08 04:14 AM
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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!
Posted By: Anonymous
Re: Is a 4.30 rear end right for me? - 08/27/08 02:24 AM
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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.
Posted By: Anonymous
Re: Is a 4.30 rear end right for me? - 08/27/08 02:50 AM
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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
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.
Posted By: SCATPK
Re: Is a 4.30 rear end right for me? - 08/27/08 05:48 AM
To much gear for a street car, go with 391`s if you must have a somewhat low gear.
Posted By: Paul_Fancsali
Re: Is a 4.30 rear end right for me? - 08/27/08 06:30 PM
I drive 110 miles to track and back with4.30s and 28.5 tall street tires. Done it with 24.5 street tires too the gas mileage is 10-11mpg not good but what do you want??? The one thing to consider is the weight of the car my car is heavy and needs the gear to get moving with a small block I ran 3.91s in the car for close to 15 years the 4.30s gave me the .25 I wanted so they stay. I have a set of 3.91 sure grip which I may install but have been leaning toward 4.56s
Posted By: RoadRunnerJD
Re: Is a 4.30 rear end right for me? - 08/28/08 02:46 AM
4.30 is a great gear for a B-body! The 2.75 r60's are about 28" which is a good diameter. It may seem much at first but you'll get used to it fast...especially if you're going to run it a lot. You will have to practice your hole shot but there won't be many on the street that will stay with you off the line.