Originally Posted by MR_P_BODY
Originally Posted by DaveRS23
As with our 727s, line pressure and valve body play a big role. And really, much of what we do for the 727 applies to the 518. The OD unit does need some attention, but nothing radical. Good clutches, more spring pressure and line pressure, proper clearances, and maybe a better bearing and cooling make the OD unit more durable.

I used a number of internet sources for my build. PATC being one that comes to mind. A Google search will bring up a number of build threads and parts sources. Don't forget to look at what the truck guys are doing. They have spent a bunch more time with these trannies than the car guys have.

The biggest issue I had was getting a torque converter that I liked for my use on the street. Most were just too loose for my liking. Lenny at Ultimate was the one who finally got me as close as I am going to get.


I have dealt with PATC while building my 518.. I did do some things differently..
mainly I used a 727 conv with a 5000 rpm stall which I have Lenny lower
the stall a little for the street.. I also used the correct front pump so the
conv would work.. still have most of the stock parts in the OD and the
valve body.. for what I know the OD spring is pretty much the same as
the diesel one so I just used the stock OD spring with the same clutches
as stock.. so if I want it to hold more power what should I be changing and
what kind of line pressure are you running(I thought the line pressure was
just to take it out of OD and the clutches held it on
thanks
wave



If you want more capacity just build the overdrive clutch like a diesel. Line pressure is the same between diesel and gas as is the large spring people call the OD spring. That spring is the direct clutch spring.
It’s used primarily for reverse but is also on in 1, 2, and third.


The 47 diesel has more frictions and steels in both the direct and overdrive clutches. The old 46 diesel had an extra OD disc and same number of direct frictions as the gas.

You don’t need to mess with the direct in a car unless you somehow figured out a way to haul a 20K pound trailer.

The later 48 diesel has even more updates in the OD but again that is driven by the increased GVW of the truck.

Last edited by Transman; 04/15/19 06:47 PM.