Engine, rear gear, Tourque Converter, Tire size info/question for the experts

[nick455440]

Little info on the car before the questions.. Some of the parts converter, rear gears, ect.. I am running becasue I already had them from picks when getting the car togeather. I have a 65 Valiant, Mild 340, Ported x heads, Comp Xtream energy cam, Holly 750bp. The trans is a 904 and have a Turbo Action 10" converter, belive its a 3500 stall. The rear is a 8 3/4 had 5:13's now has 3:73's. Its a small bolt pattern car and has custom ordered 17" rims, rear tire is a 245-40 ZR17, on a tape it seems about a 24 1/4" tall tire. The car has been on the road for a a few months. Runs very strong, fast ect.. but blows through gears, seems to run at a very high RPM. The wheels were custom order and not really a option to run a different wheel for more/taller tire options. Wanting to know if this Converter, wheel/tire hight, gear combo is just not a good combo. I am planing on in the near future trying to go with a taller tire but there is not alot of options and the ones that they have are only a bit taller. Ideally would like to keep the converter becase its a pain to swap out. I am wondering if lower gears would help and ifso what would be ideal, I was going to go with 3:55 but changed to 373 last min, wish i would have stayed with the 355's... Any and all advise is greatly appreciated, Thanks Nick

 

[318willrun]

You need to figure out if it's torque converter slippage or the gears that's making the engine sing. What is the RPM's at, let's say, 55 mph? And what happens to those RPM's if you pull a hill? A 24" tire with 373's will hum a bit lol

 

[fishmens67]

A 24" tire with 373's will hum a bit lol

like a 4.10 with 26" tires.

 

[MOPAROFFICIAL]

Little info on the car before the questions.. Some of the parts converter, rear gears, ect.. I am running becasue I already had them from picks when getting the car togeather. I have a 65 Valiant, Mild 340, Ported x heads, Comp Xtream energy cam, Holly 750bp. The trans is a 904 and have a Turbo Action 10" converter, belive its a 3500 stall. The rear is a 8 3/4 had 5:13's now has 3:73's. Its a small bolt pattern car and has custom ordered 17" rims, rear tire is a 245-40 ZR17, on a tape it seems about a 24 1/4" tall tire. The car has been on the road for a a few months. Runs very strong, fast ect.. but blows through gears, seems to run at a very high RPM. The wheels were custom order and not really a option to run a different wheel for more/taller tire options. Wanting to know if this Converter, wheel/tire hight, gear combo is just not a good combo. I am planing on in the near future trying to go with a taller tire but there is not alot of options and the ones that they have are only a bit taller. Ideally would like to keep the converter becase its a pain to swap out. I am wondering if lower gears would help and ifso what would be ideal, I was going to go with 3:55 but changed to 373 last min, wish i would have stayed with the 355's... Any and all advise is greatly appreciated, Thanks Nick

You have to get the tight version of that converter or it will be a piece of **** on the street.

 

[nick455440]

Hey 318, recognized the name but didnt realize you were on abodies, watched some of your vids when I was timing this thing, will drive it tomorrow and get some exact MPH / RPM info.

I kick myself for not going 3:55's or with that small of a tire would that still be to much gear in yalls opinion... you should have seen it for few days I put it on the road with the 5:13's (only becasue thats whats was in the chunk when i picked it up) felt like 7k driving to the mailbox

 

[unawarejez]

Hey Nick, with your 904, 3500-stall converter, 3.73 gears, and 24¼” tires, it’s normal for the car to feel rev-happy and blow through gears. The high-stall converter launches the car aggressively, and the 3.73s just keep RPMs up.
Dropping to 3.55 or 3.62 gears would lower RPMs and make it feel more balanced, especially if you can go slight taller on the tires in the future. If you stick with 3.73 and the current tires, it’s always going to feel high-rev. The combo isn’t bad, just a little aggressive for daily driving.

 

[mderoy340]

Pull the starter and remove the dust cover. The Turbo Action part # and serial # are stamped into the converter. Give them a call and they can tell you exactly what the converter specs are.
I have found that each step in gear ratio change or tire diameter increase reduces RPM by approxiametely 200 revs. I run a TA tight 10" S800 converter in my car.

 

[nick455440]

Hey, called Turbo Action the part numer on the converter is 19802S they said it was a 3500 stall and considered to be a loose converter..

 

[nick455440]

Also this car will be 95 percent street driven, would like it to be as quick a possible within reason, take to the track from time to time, def not a daily driver, a week end cruise and not really concerned abouot gas milage ect.. Thanks again

 

[MOPAROFFICIAL]

Hey, called Turbo Action the part numer on the converter is 19802S they said it was a 3500 stall and considered to be a loose converter..

Like I said...

 

[nick455440]

I may try to go with some bigger tires, may be able to go 255 50 17's in thr rear which are showing about 27" diameter, in your/yalls opintion with my set up what would be a good/better converter vs the 3500 stall/loose? Not wanting to break the bank if possible,

 

[fishmens67]

n your/yalls opintion with my set up what would be a good/better converter vs the 3500 stall/loose?

Just send your convertor out and have it reworked for your combo.
Paul at TA could probably give you a recommendation for who to send it to.

 

[TT5.9mag]

A taller tire (effectively less gear ratio) will make the converter worse. Then when you put 3:55s with it, it will get even worse. For your goals, you need a 3:23 gear and a 2800 tight converter.

 

[nick455440]

318 - driving it today the RPM at 40mph was around 2300 RPM, at 55/60 mph rpm was around 3500

 

[Icetech]

Use a rpm calc, put in your nfo.. if it says you are supposed to be at like 2700@50mph and you are at 3200.. you have slippage... if you think the TC is an issue send it to FTI.. they are great to deal with (plenty of tc companies though.. so pick one)

BTW.. 24.5 " with 3.73s should be 2550rpm... but with that tire diameter i'm betting first gear is gone almost instantly... i run 4.30s with 30" tires and am at 2450@50mph... and i rarely go over 50 due to it (no highway time) it's fun from light to light though...

You need taller tires (28" if you can) or 3.23s.. which would drop you to 1800@50

P.S. i like the 4.30s but they are very annoying... i will probably go to 3.23s when my new motor is done (one day).. and your gearing right now is worse than mine for rpm..

Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio

Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio

purperformance.com

 

[Icetech]

318 - driving it today the RPM at 40mph was around 2300 RPM, at 55/60 mph rpm was around 3500

your rpm with that setup at 40mph should be 2040... 55 would be 2813..

 

[Icetech]

just curious, if you are doing like 30 and get on it does it sound like it's slipping or does it get up and go? I have a PTC 3200 9.5" in my car right now and i can't tell the difference from a stock one unless i hammer it from a stand still. Older converters were way sloppier

 

[Icetech]

BTW.. they do make 28" tires for 17" rims... 245-60-17 tire diameter is 28.6" and would bring your rpm down a lot.. but take some fun away, they just don't say cool stuff like ZR on them

 

[middleagecrisis]

A taller tire (effectively less gear ratio) will make the converter worse. Then when you put 3:55s with it, it will get even worse. For your goals, you need a 3:23 gear and a 2800 tight converter.

It sounds like what you want is the above. I'm not sure what your cam specs are and stated rpm powerband, but for a street car your torque converter should stall at the beginning of your powerband (Minimum). So if powerband is 2000 -5500, then 1800/2200 stall is your minimum. If you were after max performance, then the converter you have would be a good choice. The tire size you have is very short, that's also a big contributor to your gear choice. The difference, all things being equal, between 3.55's and 3.70's is only a few hundred rpms. You can get rpm calculators for given mph/tire size/gear ratio online, just do a search. They don't factor in torque converter slippage,but will give you a good idea of what you can expect for your combination. I currently run a 4.11 gear, 904 with a stock type stall (1800) and a 26" tall tire (295/50/15) and turn ~3000 rpm at 60 mph. It's all a compromise, how much performance do you want vs. how much rpm you're willing to turn? Of course, a 700R or TH200-R4 with 3.70 gear would be optimal, but that's an expensive route and we work with what we have to work with.

 

[nick455440]

just curious, if you are doing like 30 and get on it does it sound like it's slipping or does it get up and go? I have a PTC 3200 9.5" in my car right now and i can't tell the difference from a stock one unless i hammer it from a stand still. Older converters were way sloppier

Its solid from a stop but like you said cruising around 30 and get on it, the acceleration def does not seem match the RPM, assuming thats the slippage. It will move but does not throw you back in the seat like it should.

 

[nick455440]

It sounds like what you want is the above. I'm not sure what your cam specs are and stated rpm powerband, but for a street car your torque converter should stall at the beginning of your powerband (Minimum). So if powerband is 2000 -5500, then 1800/2200 stall is your minimum. If you were after max performance, then the converter you have would be a good choice. The tire size you have is very short, that's also a big contributor to your gear choice. The difference, all things being equal, between 3.55's and 3.70's is only a few hundred rpms. You can get rpm calculators for given mph/tire size/gear ratio online, just do a search. They don't factor in torque converter slippage,but will give you a good idea of what you can expect for your combination. I currently run a 4.11 gear, 904 with a stock type stall (1800) and a 26" tall tire (295/50/15) and turn ~3000 rpm at 60 mph. It's all a compromise, how much performance do you want vs. how much rpm you're willing to turn? Of course, a 700R or TH200-R4 with 3.70 gear would be optimal, but that's an expensive route and we work with what we have to work with.

Hey the cam is a Comp Xtream Energy 274/286, lift .488/.491, was looking at some tires 255 50 17 shold fit under it, would ut it up to a 27" tire, in your opinion with a better converter, a 27" tire would 373/355 ish gears still be to much gear, also thanks all for the info

 

[middleagecrisis]

Here's 4.11 and 3.55 difference, everything else being equal:

Here's the website for you play around with different gear ratios and tire sizes: Calculate RPM for Given Speed(MPH), Rear Gear Ratio, and Trans Gear Ratio Is it worth the cost of a gear change worth 400 rpm? Your motor will know the difference between 3.55 and 4.11, speaking from personal experience. As I said before, it comes down to what you want and what you're willing to compromise. "What you're willing to compromise" covers a LOT of things: Top end, acceleration, gas mileage, money, on and on and on. Only you know what you want.

 

[Illahe]

Little info on the car before the questions.. Some of the parts converter, rear gears, ect.. I am running becasue I already had them from picks when getting the car togeather. I have a 65 Valiant, Mild 340, Ported x heads, Comp Xtream energy cam, Holly 750bp. The trans is a 904 and have a Turbo Action 10" converter, belive its a 3500 stall. The rear is a 8 3/4 had 5:13's now has 3:73's. Its a small bolt pattern car and has custom ordered 17" rims, rear tire is a 245-40 ZR17, on a tape it seems about a 24 1/4" tall tire. The car has been on the road for a a few months. Runs very strong, fast ect.. but blows through gears, seems to run at a very high RPM. The wheels were custom order and not really a option to run a different wheel for more/taller tire options. Wanting to know if this Converter, wheel/tire hight, gear combo is just not a good combo. I am planing on in the near future trying to go with a taller tire but there is not alot of options and the ones that they have are only a bit taller. Ideally would like to keep the converter becase its a pain to swap out. I am wondering if lower gears would help and ifso what would be ideal, I was going to go with 3:55 but changed to 373 last min, wish i would have stayed with the 355's... Any and all advise is greatly appreciated, Thanks Nick

What's your tire diameter? My 69 with 26" drag radial likes 3.91:1 5700+ at the 1320' mark with 360 ci and 246@ .050 SFT. If you don't think your torque converter is doing its job, call Dynamic Torque Converters and speak with Shane. Paul at Turbo Action is no slouch though, so I'm thinking your converter is not specked wrong

 

[AJ/FormS]

on the back;
About the smallest tire somebody might run is a 24 inch, and about the tallest that fits is a 28.
From small to big, that's a difference of 28/24= plus 16.7%
This is thus the maximum difference in your hiwayspeed, both at same slip.
A rear gear swap is a lil under 10%, ie
2.94 to 3.23 is plus 9.8%
3.23 to 3.55 is plus 9.9%
3.55 to 3.91 is plus 10%
3.91 to 4.30, is plus 10%
3.73s and 4.10s are half-gears at about 5%.

As for overdrives;
You got about the right gear for use with the Mopar .69 overdrive.
3.73 x .69= a final-drive ratio of 2.57, and 65= 2100, in lock-up.
But, if yur running headers, that cam will likely suck gas big-time at 2100 in steadystate. Yur a good two cam-sizes too big for 2.57,
OR
a good two rear gear sizes too small for that cam.

 

[nick455440]

A taller tire (effectively less gear ratio) will make the converter worse. Then when you put 3:55s with it, it will get even worse. For your goals, you need a 3:23 gear and a 2800 tight converter.

Hey i pulled the cam I have up in Summit it shows the RPM range from 1,800 to 6,000 several on here agree with your 2800 tight converter recomdation, I know most converters have a range, 2800-3200 ect.. should i be looking for the 2800 to be at the higher end or the lower end of that range? Thanks again, Also on summit there were some recomendations for that cam to have a converter 2300-2500 but this was just a generic responce to cam alone that someone had asked,