ok so im trying to pick between a 518 and a getrag i plan on doing hp mods and i was wondering how well does the 518 hold up

 

torque converters need to be upgraded as well as valve body and a shift kit.

5 speed all the way, but thats just my opinion

 

depends, you want to pull something or go fast?

 

Exactly! Towing 5sp, no question. OTOH despite running really well, with non-abusive shifting, my truck is lucky if it's quick enough to get out of it's own way through the 1st three gears.

 

I'd say Getrag too. Much less loss through the tranny.

 

well how much power will the 518 stock hold up to and why do u need a better converter what happens with the stock one under alot of power

 

The factory convertors suck, plain and simple, I've heard as much as 40% power loos through a old factory one. The newer aftermarkrt ones have as little as 8% loss. Under alot of power nothing bad really happens, they wont transmit enough of it to really hurt themselves ... But your not getting that power to the wheels. They suck up ALOT!!!

 

Stock transmission good for around 225 whp.

 

I know alot of people that have put more then that through a stock tranny.

 

I have 296 hp through my stock 727 tranny in my 89.