I have the 518 in my 92 D150 which I bracket race on occasion, when racing I always push the o/d off button on the dash if I don`t it goes into o/d which slows the truck quite a bit. I have a Mopar Performance/ Turbo-Action shift kit , the 1st to 2nd shift is quite hard even under normal driving but it works well. I was going to add an off the shelf convertor to try and get the truck to leave better, instead Lenny at Ultimate said he could rework my stock lockup convertor which he did and the truck responded well although it only runs low 15s my 60ft times dropped from high 2 teens- low 2 twenties to low/ mid 2.0s a little over a tenth.
So you have just a bit over stock stall... I checked into
a lock up high stall conv.. 5000 stall and it was
$1800 for a conv.. and he didnt know if the LU clutch
would live... he wanted to make it about a 1" thicker
so I would have needed a 1" spacer between the engine
and trans... most of the conv places that I talked to
wanted to go thicker if I wanted the stall I was looking
for... right now I'm using the old J-conv from T/A and
when I talked to Paul about the slippage it didnt know
for fact what it would be in OD... he said 10%... he was
close... its 9% at 75 mph.. I havent seen any issue with
trans temp.. I normally see about 180* on a long run(75 miles
or more).. but I run a nice size cooler.. and if I needed more
I have another with a fan that I would add to it also
EDIT
This slippage data was when I was still having issues
with the trans.. it was eating itself up due to no
torrington bearing in the OD.. so I will need to do
a new set of numbers since this last time of going
through the trans.. I expect it to be better now
