PM me and I will explain it in detail.
I do not want to hyjack someone else thread
Appreciate your patience
I do not want to hyjack someone else thread
Appreciate your patience
Ballpark Gear Ratio
- Thread starter SpeedThrills
- Start date
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QuickDart360
Well-Known Member
Anything special done to thermoquad for running in the 10's?
If it helps, I just made the switch about 6 weeks ago in my avatar car. Went from 4.56 to 4.10's. Engine is a 408 w/ Eddie RPM's mild porting, 251/255@050 cam, Super Victor, 850DP, 10.5 cr. 28x10.5W bias slick w/CalTrac split mono leafs. 5000 stall 8" ATI Treemaster converter. Cage, subframes tied. Weight unknown but guessing around 3400 with me in it. The car was not 100% dialed in (and still isnt!) but close enough for this topic/comparison.
The 4.56's wanted to trap in the 6700+ rpm area and I know this stroker motor's power peak is somewhere in the 5700-5900 range. So that rpm is too high. Best was an 11.31 @ 115.
Swapped in the 4.10's. At roughly 1000 worse DA (roughly 3000 DA), the car has now run an 11.25@117. It traps close to 6200 now - exactly where I hoped it would. I share a little running log of the car in the thread "The 72 Demon Follies...".
Note that I use a spool with both ratios. The suspension works really well so tire spin has not been an issue with either axle.
IMHO...I would go with a 4.10. I doubt many of us (certainly not me!!) will ever reach the power and chassis expertise that GTX JOHN has in his cars hence a little more axle than his 3.91 may help. My $.02.
The 4.56's wanted to trap in the 6700+ rpm area and I know this stroker motor's power peak is somewhere in the 5700-5900 range. So that rpm is too high. Best was an 11.31 @ 115.
Swapped in the 4.10's. At roughly 1000 worse DA (roughly 3000 DA), the car has now run an 11.25@117. It traps close to 6200 now - exactly where I hoped it would. I share a little running log of the car in the thread "The 72 Demon Follies...".
Note that I use a spool with both ratios. The suspension works really well so tire spin has not been an issue with either axle.
IMHO...I would go with a 4.10. I doubt many of us (certainly not me!!) will ever reach the power and chassis expertise that GTX JOHN has in his cars hence a little more axle than his 3.91 may help. My $.02.
Use this link> ET/MPH From Horsepower Calculators
Add in your estimated fwhp/and the rest of your parameters/weight ratio's tyre size to get an ET etc. etc., add converter slip to the trap rpm which can be 4>10%?. Play around with it and you'll see the differences. Been doing it since 1990, was quite accurate for all my cars back then and still is today.
Add in your estimated fwhp/and the rest of your parameters/weight ratio's tyre size to get an ET etc. etc., add converter slip to the trap rpm which can be 4>10%?. Play around with it and you'll see the differences. Been doing it since 1990, was quite accurate for all my cars back then and still is today.
So who sells a good (street) ring and pinion these days? It's been 20 years since I bought gears. I'm going with 4.30's.
It looks like Ratech has the installation stuff (bearings, etc.). I'm getting their pinion depth tool, reusable gasket, and solid spacer, too.
Ratech
I see Randy's and Moser are priced 3-400. Then I see Motive and US Gear for about 250-300.
I guess there's even Chinese junk in the equation now? I see no-name gears for 100-150 on Amazon.
It looks like Ratech has the installation stuff (bearings, etc.). I'm getting their pinion depth tool, reusable gasket, and solid spacer, too.
Ratech
I see Randy's and Moser are priced 3-400. Then I see Motive and US Gear for about 250-300.
I guess there's even Chinese junk in the equation now? I see no-name gears for 100-150 on Amazon.
QuickDart360
Well-Known Member
I went with US gear. Guy that set my gears up said they were pretty easy to set up. Runs nice and quiet! I once saw a company called Tom's differentials carry US gear for mopars.
33IMP
Well-Known Member
I think the no-name gears are made in India. I even think some of the name brands are too.
B3422w5
Well-Known Member
everything is trick on most every competitive stocker/ super stocker in the country.
Howling aside, how is it on a run? What rpm’s you seeing after 1st-2nd and 2nd-3rd? With 26” tires I’d think you’d want to stick with 4.10’s
If for some reason you think you might step up to 28” tires I’d go with a 4.30
If for some reason you think you might step up to 28” tires I’d go with a 4.30
I haven’t had it down the track yet. So I have no trap RPM, mph or anything. I am going to use 4.30’s.
33IMP
Well-Known Member
I think 4.30 is a workable choice, especially if going to a taller tire in the future. I might have chosen 4.10. I have had 4.56s, 4.10s, and 3.91s in mine, and it didn't change E.T., but I've got a 440, and spinning it real high rpm is counter productive.
Seeing that you have a nine inch, are you gonna run a spool, or some sort of lsd? Ford "posi's" are not some of the best. I have a spool in one of mine, gonna try a lock-rite in my other one.
If you don't want a spool, imo a Detroit locker would be the best choice.
I don't want a spool, it gets used on the street, though not much.
It has a LSD, I'll have to see what kind of shape it's in.
Maybe a reason to consider a spool.
I think these center sections are heavier than they used to be. When I was 20, I would send it under the car on a creeper. Then get under there and slide it onto my chest. From there, I'd just push it up and in. I tried that this time (I'm 63). I thought my brain's message to push up wasn't getting to my arms. Nothing happened. 
Turns out my brain is okay. It made me go buy a transmission jack. It was still somewhat of a challenge, but it went.
(Oh, nobody around to help. I'm used to that where I live.)
I used Richmond 4.33's. I put new clutches in the factory Traction Lock, and new bearings.
Anyhow, I ran it on jack stands today, and it seemed okay. Then, I took it for an easy 13 mile ride. All is good. It's not perfectly quiet, but the car has polyurethane bushings, and no sound insulation, so it's going to make some noise.
Thanks again for the help.
Turns out my brain is okay. It made me go buy a transmission jack. It was still somewhat of a challenge, but it went.
(Oh, nobody around to help. I'm used to that where I live.)
I used Richmond 4.33's. I put new clutches in the factory Traction Lock, and new bearings.
Anyhow, I ran it on jack stands today, and it seemed okay. Then, I took it for an easy 13 mile ride. All is good. It's not perfectly quiet, but the car has polyurethane bushings, and no sound insulation, so it's going to make some noise.
Thanks again for the help.
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