[ukko]

So, why would I want to do such a stupid thing?

I am having issues with the transmission in my P38 where the Gearbox fault triggers at speed. This puts it into limp mode in 4th gear. If I could get it to fault while stationary that would put it in 3rd gear for limp mode. I have been troubleshooting this and really have run out of options so I think it will be easier to just get a new transmission and go from there. That involves driving across the city, and I really think limping in 3rd would be better, since you really cannot accelerate from a stop in 4th.

Is there a clever trick to accomplish this?

Thanks!

 

[95classiclwb]

have you tried manual shifting to a lower gear, this should override the ecu's logic.

 

[ukko]

The easiest way to find an answer is to ask a silly question, to quote the transmission manual:

Mechanical Limp Home

In the mechanical limp home mode in high range,
gear engagement is controlled by the manual valve.
The gearbox is fixed in 4th gear if the fault occurs
while the vehicle is moving, or 3rd gear if the fault
occurs while the vehicle is stationary. 3rd gear is also
engaged if a vehicle is brought to a stop and the
selector lever is moved out of, and back into, D.​

So, I can get it into 3rd with that one simple trick ;-)

I had tried to shift to a lower gear while moving but once it is in limp mode it does not obey the lower gear requests. The trick is to do it while stopped. You still only can get to 3rd that way, but that is an improvement.

 

[95classiclwb]

ok, answer found lol. good luck.

 

[Escape]

Or unplug the ECU, that will give you 3rd gear when in D (or 3-2-1).

 

[dave3d]

I think the transfer box will still work in limp mode. Although not sure because the last time my car went into limp mode was about 8 years ago. Mine was locked in 3rd gear but was a soft fault that cleared by recycling the ignition.
If you are just moving it across town, you could run it in 3rd gear low ratio which will probably give you a top speed around 25mph but will be a lot easier to pull away.