Just bought everything for 3.73 gears

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ProSport said:
GER was the worst converter company on the face of the earth.



I've always used this RPM calculator, it's very simple and accurate.
https://www.ringpinion.com/Calculators/Calc_RPM.aspx

Original poster, what motor are you running?
I've read alot of threads about highway gearing and have one of my own and for the most part they're just a pee'ing match since it's all about personal preference. Some guys are fine with roaring down the highway at 3800 RPM's. I am not ok with that as it just simply annoys me.

My Duster has a 500" big block with a 727, 9.5" Dynamic converter, and an 8.75 with 3.55 gears along with rear tires that are 27.5" tall. I'm at 2800 RPM's at 65mph, yesterday I installed 3.23 gears which should bring it down to around 2400 RPM's.
When I have the energy, hopefully soon, I want to pull the 9.5" Dynamic and sell it or trade it for a tighter 10" converter. I drive my car alot and the motor has so much torque that the 3.55 gears feel like 4.10's so I'm thinking I'm gonna like the 3.23's.
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I prefer to go to taller tires if possible to help these situations. also my hughs 3500 convertor seems awful loose, haven`t got to do any driving much w/ it yet tho. guessing from passed experience it`ll flash at least 4000-4200. have 28" rear drag radials on tit now, will go to a 29" eventually.-------505" 68 barracuda, 3;73 dana , 727 auto. ported alum. heads, fst 2.0 fuel I. ,
 
I'm running a 275/60/15, that's as tall as I can go.
Sounds like a nice combo in your Cuda.
 
famous bob said:
I prefer to go to taller tires if possible to help these situations. also my hughs 3500 convertor seems awful loose, haven`t got to do any driving much w/ it yet tho. guessing from passed experience it`ll flash at least 4000-4200. have 28" rear drag radials on tit now, will go to a 29" eventually.-------505" 68 barracuda, 3;73 dana , 727 auto. ported alum. heads, fst 2.0 fuel I. ,
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What a converter flashes is dependent on quite a few things. One of which is anytime you put a 505" engine in front of any converter it's going to feel lose because of the massive torque a huge engine like that makes. My PTC 3500 flashes over 4000 with my torquey little 408 yet it doesn't feel lose when I cruise it. Remember also that converters are rated 2 ways. Brake stall and flash stall. Flash stall with a big cube block is almost always going to be quite a bit more than brake stall. Also remember this, taller tires weigh more so they'll cause the converter to work more, which equals more slippage and quite possibly more stall
 
fishy68 said:
What a converter flashes is dependent on quite a few things. One of which is anytime you put a 505" engine in front of any converter it's going to feel lose because of the massive torque a huge engine like that makes. My PTC 3500 flashes over 4000 with my torquey little 408 yet it doesn't feel lose when I cruise it. Remember also that converters are rated 2 ways. Brake stall and flash stall. Flash stall with a big cube block is almost always going to be quite a bit more than brake stall. Also remember this, taller tires weigh more so they'll cause the converter to work more, which equals more slippage and quite possibly more stall
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yup. thinkin it`ll pullem. lol
 
Well I got the new pinion yoke, for a 7260 joint, I based mine off measurements, 1" diameter cap so crossing my fingers it will work..

I will probably swap the gears, as I can live with 3,200rpm or so cruising at 70mph plus paying a friend $50 to do the swap - that's what my old 5 speed fox was with 4.30's though haha plus it will be less load on everything as I plan to race the car on and off the track with drag radials, and don't want to make snapping a U joint easier than it has to be..
 
So getting ready to swap the gears, I have4 a really great shape 741 case, bearings, and seals frankly..

My install kit didn't come with a crush sleeve, my 68 service manual says "spacer" with shims on either side

Is this correct? I've never had one of these apart, nor has my friend that I'll be helping do the swap.. HELP!
 
zac_F71 said:
So getting ready to swap the gears, I have4 a really great shape 741 case, bearings, and seals frankly..

My install kit didn't come with a crush sleeve, my 68 service manual says "spacer" with shims on either side

Only the 489 uses a crush sleeve. Your 741 has a sleeve and uses thin shims. When you take it apart you can see that easily
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Do what we all did before the fancy shmancy internet and all these calculators. Grow a pair, make a decision, put some gears in. If you don't like it, change it again. Gears are what......150 bucks?
 
It's getting 3.73's, not worried at all, but my friend has never done gears in an 8 3/4, and neither have I so I'm trying to educate myself on the process before taking apart a perfectly good center section..
 
RustyRatRod said:
Do what we all did before the fancy shmancy internet and all these calculators. Grow a pair, make a decision, put some gears in. If you don't like it, change it again. Gears are what......150 bucks?
Click to expand...

LOL, that's the primitive caveman approach. Nothing wrong with asking advice from people who have already been there, and the RPM calculators are great, I use the one on Randy's ring and pinion page and it's always accurate.

When I raced for 21 years I would just throw 4.56 gears and an 8" converter in the car and go racing. Now that I have a street car I play around with gearing and hope to try a tighter converter soon, it's way cheaper than paying for an overdrive setup.
 
69_340_GTS said:
70 mph = 3133 rpm
60 mph = 2685 rpm

Here's the calculator: http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php
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Plus TC slip, if an auto.Which shouldn't be much in a lightweight Demon;100 to 150 rpm.
Sometimes it goes backwards. With a torquey engine, and a tight TC,at 60/65 mph, I have had cars the actually cruise at less than the Zero-slip calculated rpm. Some were over 100 rpm lower.How does that work? IDK.
 
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