converter hurt the tranny?
06-23-2006, 12:18 PM
#2
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
"Perhaps".
Most high-stall-speed converters also have a high
torque multiplication, and put the big multiplication
onto a motor torque that's closer to peak (the stock
one fades way early, multiplies less of an off-peak
torque). So you're putting the double whammy on
it, leaving aside that usually people put big converters
on motors already modded to higher torque levels. So
you have a greatly increased input shaft torque and
the stock trans has some known weaknesses in that
area. Then again so does the stock rear, and the
middle and back bits of the trans are only waiting for
you to beef up the front so they can taste the pain.
Here's the stock setup - 1800 stall, 1.8 STR, 250 lb-ft
at 2500RPM or so (peak, is higher RPM). Maybe an
applied 450 lb-ft at the shaft, off the line.
Here's your street converter setup - 3500 stall, 2.5
STR, 350 lb-ft at 4500RPM. The converter will let you
slide on up to peak torque, call this a mild bolt-ons car.
Applied shaft torque off the line, 875 lb-ft.
Here's your high-11s car - 4400 stall, 2.7 STR, 450 lb-ft
at 5500RPM and dead-hooking on slicks with a good
suspension. Shaft torque is 1215 lb-ft or so. Sound good
against a trans that GM sort-of rates at 600lb-ft? You
can bet there's no 100% safety margin built in, no sir.
Moderate converters, lower STRs, less of a risk, but
you will not know if you got the pick of the litter or a
runt until you crack the whip.
Most high-stall-speed converters also have a high
torque multiplication, and put the big multiplication
onto a motor torque that's closer to peak (the stock
one fades way early, multiplies less of an off-peak
torque). So you're putting the double whammy on
it, leaving aside that usually people put big converters
on motors already modded to higher torque levels. So
you have a greatly increased input shaft torque and
the stock trans has some known weaknesses in that
area. Then again so does the stock rear, and the
middle and back bits of the trans are only waiting for
you to beef up the front so they can taste the pain.
Here's the stock setup - 1800 stall, 1.8 STR, 250 lb-ft
at 2500RPM or so (peak, is higher RPM). Maybe an
applied 450 lb-ft at the shaft, off the line.
Here's your street converter setup - 3500 stall, 2.5
STR, 350 lb-ft at 4500RPM. The converter will let you
slide on up to peak torque, call this a mild bolt-ons car.
Applied shaft torque off the line, 875 lb-ft.
Here's your high-11s car - 4400 stall, 2.7 STR, 450 lb-ft
at 5500RPM and dead-hooking on slicks with a good
suspension. Shaft torque is 1215 lb-ft or so. Sound good
against a trans that GM sort-of rates at 600lb-ft? You
can bet there's no 100% safety margin built in, no sir.
Moderate converters, lower STRs, less of a risk, but
you will not know if you got the pick of the litter or a
runt until you crack the whip.