Re: Does gear ratio change impact torque converter ?
[Re: A990]
#503093
10/21/09 08:29 PM
10/21/09 08:29 PM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
Okay imagine a highly optimized race car thats setup with 4.56 gears. Then change to a 3.55 gear. Will that make the TC less effective on the launch? By much or so little it wont matter?
Im debating a combo that will have a 3.92, 4.10 or 4.56 gear choice. How much will the TC role play in such a senario?
Any input is appreciated
It wont change the torque converter... BUT you will
see a difference in total torque(torque of the engine
hasnt changed which will effect the converter)
but the total torque will (engine torque x converter,
usually 2 x at launch x gear in the trans x the
rear ratio and then tire diameter)
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: MR_P_BODY]
#503094
10/21/09 10:54 PM
10/21/09 10:54 PM
|
Anonymous
Unregistered
|
Anonymous
Unregistered
|
It makes the converter multiply torque longer by going to a higher gear........
I've done a LOT of converter/gear ratio testing and I've seen very little, if ANY ET change by going to a higher gear IF if the converter is right for the motor.........
On your contemplated build up, what's the car weigh, what's the motor buildup, what converter is in it, and what's it ET and MPH now?
Small, high RPM, peaky motor will have a larger ET loss than a big, low RPM torque motor.......
|
|
|
Re: Does gear ratio change impact torque converter ?
#503096
10/22/09 04:29 PM
10/22/09 04:29 PM
|
Joined: Jan 2003
Posts: 2,730
541 slobovia
A990
OP
master
|
OP
master
Joined: Jan 2003
Posts: 2,730
541 slobovia
|
The combo will be a 99 Dakota R/T regular cab, and its kinda heavy (like 4,000 lbs).
I'm looking into turbocharging it, going through the 5.9 and getting some better heads and cam. It will be dual purpose, mostly street, but since the EFI will need tweaked, I'm gonna get rid of the lockup convertor for something matched with turbo spoolup and so forth.
The RT folks most always switch to 4.56 gears, but if my setup will be OK on the stock 3.92s, I see no reason to switch.
Based on street use, I dont think an 8" converter will be ideal though lol
Thanks for the replies
Ken
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: A990]
#503097
10/22/09 04:59 PM
10/22/09 04:59 PM
|
Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
|
master
Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
|
Once you included "turbo" in the combo, everything changes, and big. A turbo motor will have so much more torque the 3.92 gears may even be too much . How much boost you going to put to it? How tall is the low gear ratio?
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: gregsdart]
#503099
10/22/09 07:06 PM
10/22/09 07:06 PM
|
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
|
Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
|
Quote:
Once you included "turbo" in the combo, everything changes, and big. A turbo motor will have so much more torque the 3.92 gears may even be too much . How much boost you going to put to it? How tall is the low gear ratio?
 With a turbo you will increase the torque
of the engine(will depend on the boost)which in change
WILL change the stall of the converter
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: MR_P_BODY]
#503100
10/22/09 07:17 PM
10/22/09 07:17 PM
|
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
|
Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
|
be prepared for mid 11s EASY with that truck, even if it DOES weigh 4,000 lbs.
there's a guy on Dakota-Durango.com with a 408 stroker, Turbo Dakota R/T, just ran a best of 10.5 last weekend
and what makes me feel good about it, he did it on the same "stock" 9.25 axle that I'm running!
**Photobucket sucks**
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: 70Cuda383]
#503102
10/22/09 08:50 PM
10/22/09 08:50 PM
|
Joined: Jan 2003
Posts: 2,730
541 slobovia
A990
OP
master
|
OP
master
Joined: Jan 2003
Posts: 2,730
541 slobovia
|
WOW, 10.50@130+ is bookin right along, and in a clubcab at that. I knew 9.25s are good axles, but it makes 8.75s look lame I got lots of research still to do, but I guess I'd start somewhere. Wonder then if 3.73s or 3.55s would work even better. I presume the other truck is running Cal-tracs?
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: A990]
#503103
10/22/09 09:14 PM
10/22/09 09:14 PM
|
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
|
Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
|
I don't know what suspension mods he has done. but yea, probably running cal-tracs. he's just on the stock 3.92s but upgraded the diff to a detroit from the stock LSD. he's still on the stock drive shafts, and as far as I know, a relatively stock trans, but I may be wrong about the trans. as far as gears, I went with 4.56s in my NA big block dakota, and on street tires, 1st gear is a waste, it'll roast 2nd gear from a 20-30 mph roll, but with my TKO, it'll still do 75mph down the freeway at a leisurely 2500 rpm. going to the track this weekend to see what it'll do, but I don't have any good tires to put under it, so I'm gonna be peddaling it hard! 
**Photobucket sucks**
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: MR_P_BODY]
#503104
10/23/09 07:32 AM
10/23/09 07:32 AM
|
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
|
Quote:
Quote:
Okay imagine a highly optimized race car thats setup with 4.56 gears. Then change to a 3.55 gear. Will that make the TC less effective on the launch? By much or so little it wont matter?
Im debating a combo that will have a 3.92, 4.10 or 4.56 gear choice. How much will the TC role play in such a senario?
Any input is appreciated
It wont change the torque converter... BUT you will
see a difference in total torque(torque of the engine
hasnt changed which will effect the converter)
but the total torque will (engine torque x converter,
usually 2 x at launch x gear in the trans x the
rear ratio and then tire diameter)
theoretically, going from say a 4.56 to a 3.23, shouldn't it stall *slightly* higher because you've changed the mechanical advantage on the output side, similarly to a TC should stall slightly higher in a heavier car than a lighter car if they have the same drivetrain?
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: patrick]
#503105
10/23/09 09:29 AM
10/23/09 09:29 AM
|
Joined: Oct 2004
Posts: 8,165
Left Coast
BobR
master
|
master
Joined: Oct 2004
Posts: 8,165
Left Coast
|
Quote:
Quote:
Quote:
Okay imagine a highly optimized race car thats setup with 4.56 gears. Then change to a 3.55 gear. Will that make the TC less effective on the launch? By much or so little it wont matter?
Im debating a combo that will have a 3.92, 4.10 or 4.56 gear choice. How much will the TC role play in such a senario?
Any input is appreciated
It wont change the torque converter... BUT you will
see a difference in total torque(torque of the engine
hasnt changed which will effect the converter)
but the total torque will (engine torque x converter,
usually 2 x at launch x gear in the trans x the
rear ratio and then tire diameter)
theoretically, going from say a 4.56 to a 3.23, shouldn't it stall *slightly* higher because you've changed the mechanical advantage on the output side, similarly to a TC should stall slightly higher in a heavier car than a lighter car if they have the same drivetrain?
Going from 4.56 to a 3.23 will make the converter less efficient(slip more) and vise versa.
|
|
|
Re: Does gear ratio change impact torque converter ?
[Re: can.al]
#503107
10/23/09 01:10 PM
10/23/09 01:10 PM
|
Joined: Oct 2004
Posts: 8,165
Left Coast
BobR
master
|
master
Joined: Oct 2004
Posts: 8,165
Left Coast
|
Quote:
I had my converter built for my engine/duster combo by one of the popular companies and am very pleased.
Thought I'd change from yhe 3.23 rear to a 3.55 so I asked what effect it would have.The builder told me my flash stahl would go from about 3000 to about 2800.Also mentioned they would re-adjust if necessary........al
Sounds about right.
|
|
|
|
|
It seemed like it spent a lot longer time in third gear and the motor seemed lazy with the 3:73 versue the higher ratio but the time slips where the same 
