changing gearbox automatic transmission

Post by **charlyW** » 08 May 2012, 13:36

I'm thinking about changing my ageing AW50-42LE autobox for a later AW50-50 series. I've found a post where the user went downwards ie to the 42LE series so would like to know what obsticles will I have to overcome to fit a later automatic gearbox in my 97 850 T5 RHD UK Spec

Post by **jimmy57** » 08 May 2012, 18:06

The aw 55-50 requires networked control modules as there was not a TCM made for the 5 speed when non -networked Volvo FWD models were produced.
I am aware of persons wanting to go to 4 speeds in later 5 speed cars but not of any being successful at it for the same reasons.

Post by **charlyW** » 09 May 2012, 03:39

Ok what's a networked control module, is it similar to a router connecting my computers together? If I took the entire loom from the later vehicle along with the gearbox and ECU's would I be able to configure my 850 T5's to communicate ? After all the engines are more or less the same it's the electronic life support that differs mildly.

Post by **jimmy57** » 09 May 2012, 08:56

The information on the non-networked cars exchanged between computers is done one or two wires per signal. Networked are mutliple signal messages on a common message system using two wires carrying identical information messages. More info and much quicker on networked.
The HUGE problem is the 5 speeds have a completely different algorithm used to accomplish the gear changes with double the shift solenoids compared to 4 speeds. The processor for 5 speed shift control is hugely more capable than 4 speeds computer processor.
In other words, to use a 5 speed in an older car would require someone to custom make some converter box hardware and develop the software to convert the mix of analog and digital info on your 97 into a data stream a trans control module for a 5 speed can use.
And then the 5 speed TCM would probably need a custom written software to make it fit this custom system.
A further tidbit is the 4 speeds used for 96-98 w/o network and the 99-2000 w/network are the same hardware but some of the sensors providing info to the TCM are digital on the 99-2000.