GregWS6&z28

iTrader: (8)

ive calculated my Yank ST3800 to be about 90% efficient. 10% slippage sounds like too much. Is this anything that I should be worried about? I hate leaving 4% more on table but if thats normal with a converter with maybe 15K miles and maybe 50 passes total then so be it. what do you guys think???

JNorris

iTrader: (4)

At what RPM and in what gear was the 90% measured at?
What rear gear ratio are you running?


John

GregWS6&z28

iTrader: (8)

5570, 113mph, 3.42's
i run MT ET radials which are 275/50-16 and calculate to be 25.83" tall.

it's in 3rd gear at the top of the traps 1:1

Yank

iTrader: (181)

Peak eff. is best checked at Max. RPM and checked at the top of second gear
at the point the car stops pulling (this is the point power transfer is stable) that will yield the best result without a converter dyno
to test it in high gear you must run a lot of rear end ratio, more is better -- 4.88 up

GregWS6&z28

iTrader: (8)

so would the loss of efficiency on the top end be result of a higher STR?

so I need to look at my log right at the top of 2nd before it shifts into 3rd and calculate... what is the gear ratio of 2nd that I need to use in my equation? i'm running a built 60E with stock gear ratios.

thanks
BTW, Yank, I sent y'all a message on your website before I posted here.

Yank

iTrader: (181)

second gear is 1.63:1
the St3800 when new run about 93 to 93.5 %
with fresh ATF installed

GregWS6&z28

iTrader: (8)

THANKS MUCH. I'd say my fluid is pretty fresh. i've got about 2K miles on a freshly built 60E

also something I had added.... (on highway)in 4th and locked up, with load on the car (increasing throttle % but trying not to unlock the converter) it has a violent shudder/shake. what could be the cause of this? it's usually around 70-80mph and it doesnt "seem" to happen in drive.

JNorris

iTrader: (4)

In overdrive you loose the advantage of gearing or more specifically you have less gear advantage with a .75 overdrive gear than you do in your 1:1 drive gear. This puts more load on the TC clutch. It sounds to me like you have a slipping lockup clutch.

John

JNorris

iTrader: (4)

Mike - I thought you were suppose to check TC efficiency in your 1:1 gear. There is no question that TC efficiency would be better at 6000rpm in 2nd gear than it would be at 6000 rpm in 3rd gear because of gearing advantage.

John

Yank

iTrader: (181)

If you can top out your MPH to the point the car will nose over you can test in high gear but like I stated you need a lot of gear to Peak the converter like a 4.88 or more

GregWS6&z28

iTrader: (8)

calculating at the top of second yields 6.44%. granted that put it right in line with the converter claim but I'm thinking that i should be seeing more than 10% in 1:1 gearing?

I was wondering if my lockup clutch is starting to wear out. Yank, does that sound like a reasonable explanation for my highway driving?

Yank

iTrader: (181)

The more gear the ligher the WOT work load.
In high gear at WOT you have other things that will change the shape of the converter eff. slope from car to car (wind drag,tire tread, brake drag, temp and other factors due to speed )

when you clutch is locked you will see little to no slip or 100% input to output power.

The converter is a torque meter so if you are working it in a high torque RPM range it has to work harder, like 4600 to 5400 RPM after 5600 or so (depends on cam) the torque is on the down slope so the work load is reduced and eff. will rise, that is why Drag cars over gear so at the finish line they get the most out of the engine, converter and they are on max revs and see high eff. #'s from small very high stall converters like 7" and 8" models

also note that any slip to drop back RPM will give you some extra boost from a little remaining STR

parts will and do get used up in time and use will change the internal clearances so check ups are a good idea if you have a concern

BlackHawk T/A

iTrader: (3)

Or PWM?

Does the new transmission have a shift kit?

jimmyblue

iTrader: (11)

Depending on the converter, its STR, you may not be fully
done multiplying torque. Can't say about the Yank piece's
particulars. If you have any torque multiplication going on
then pure slip-based calculations aren't telling the whole
efficiency story. I know my 3500 has not reached peak by
6000RPM. A high stall speed converter wants a high shift
point, if the rest of the setup is up to it.

GregWS6&z28

iTrader: (8)

yes i have a shift kit that shifts VERY hard and was set up that way.
i have my shift points at 6100 for each shift. ive done alot of the tuning myself. the STR is about 2.5 from what Yank has told me before. my valvetrain is upgraded minus the pushrods. but no problems on those ever since ive had the car.

I can find a way to post my HPT log if it would help discern anything

JNorris

iTrader: (4)

How are calculating TC efficiency?

John

GregWS6&z28

iTrader: (8)

with this site
http://www.tciauto.com/tech_info/calculators.htm#4

but i also read that you can use a mph calculator and then divide your actual mph/theoretical mph and that ratio is your converter efficiency.

98LS1_13.20

Get a manual transmission ya *****.

Charles

JNorris

iTrader: (4)

Neat calculator.

I have measured the torque converter efficiency by dividing the
Transmission Input Shaft RPM by the Engine RPM at WOT during a ¼ mile run.
1st gear (3.06:1) will show the best efficiency, 2nd gear (1.63:1) the
efficiency will be lower and 3rd gear (1:1) will be the lowest. You can use most scan tools to monitor these engine parameters.

John