51MercCoe

Hi all,

I have an 51 Mercury M5 cabover and I have a deal pending on an 2003 LQ9 with low miles I would like to swap in. My problem is the transmission. I would like a 6 speed over a 4 speed as I intend to use this truck to haul a vintage trailer. As I understand, the 6L90 will not work with this older engine and I might be limited to either a 2006 or later Allison 1000 or using a 4l80E with an over/underdrive from gearvendors or something.

Does anyone know if an Allison can be made to work with this engine? I would like to avoid the additional cost of an over/underdrive if I can but I haven't been able to find an answer either way using the google.

mrvedit

The 4L80E has an overdrive 4th gear; you would need need a gearvendors unit. A 6L90E has a wider gear ratio range. It will bolt up to any LSx engine, but you need an expensive aftermarket trans controller from PCS to run it.

51MercCoe

Thanks so much for the info! I am sure the cost of this controller will be less than a custom built 6 speed 4L80E or the gearvendors option. Looks like it will work with the Allison 1000 also but I have requested some more info regarding my build.

51MercCoe

Well, that's a bust.

"Thank you for your interest in PCS products. We don't support the GM 6L transmissions or Allison transmissions with harness or caibrations. Our TCM-2650 is a controller available to vehicle manufactures and OEM customers only. Sorry"

mrvedit

Strange.
I think a couple of the (non-sponsor) vendors here sell the PCS controller.