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1993 Brooklands Transmission Issue - Check Gearbox - Limp Mode

634 Views 15 Replies 5 Participants Last post by  alabbasi
My 1993 Bentley Brooklands (with 63K miles on the clock) occasionally says CHECK GEARBOX goes into 'limp' mode, meaning I'm stuck in 2nd gear until I cycle the key. It seems to happen when the car has to make a decision about downshifting and gets confused. It's fine on the highway, but gets confused when I exit the highway and it needs to come out of overdrive and downshift.

Some notes:
  • I've replaced the 1-2 and 3-4 solenoids with no luck.
  • Trans fluid has been changed and is at normal level
  • It only does this when the engine reaches normal operating temperature (won't do it if cold)
  • It seems to have something to do with the transmission coming out of overdrive
  • Transmission seems to work fine otherwise. Works fine once the key is cycled but may go into 'limp' mode again shortly thereafter.
  • Car behaves normally on the highway; this only occurs when coming off of a drive at highway speeds
  • All connections, wiring, etc. have been double-checked.

Can anyone provide any insight? Or does anyone have a similar issue?

Idea for a quick fix: Since this only happens when the transmission senses that the car is at 'normal' operating temperature, is there a way to stop the transmission from receiving the coolant temperature?

Any help is appreciated.
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I would suggest finding a mechanic who has the RR Mastercheck or Omitec diagnostic tools or renting one of them and interrogating the transmission ECU, that should identify the issue if the fault is electronic.
Thanks Jim.

I've spoken to JE Robison Service - they seem to be the perfect guys to do this and have all the tools. The trick is getting the car from here (Chicago) to them in Massachusetts... If I'm unable to resolve the issue, I will run the car up to them.

Do you know of anyone more local to Chicago that has the correct diagnostic tools?
Robison is a very good choice, but why don't you rent the Mastercheck or Omitec from Flying Spares and do it yourself? I don't know of anyone closer that would have those. I do, but I won't ship them across the border.

In my moderator role, please note that you should not quote a previous post when you reply to one in a topic if you are following the train of thought in the thread. It just clutters up the thread and is not necessary.
Sounds like you need one of my bypass modules for the transmission ECU. I still have a healthy stock the price is still $75

Video here for details:
Call the service department at Steve Foley R-R in Northbrook. They maintain both of my SZ cars, though they are a little earlier (20,000 series) than yours.
Foley did take a look at this issue a couple of years back. They said they went through the trans as best they could, replaced all the solenoids, it was $2,500 or so. However, the issue re-occurred shortly thereafter.

They didn't seem that excited about working on a 1993 car...
I did see that video and thought that was a similar issue.

Where is that module he is referring to located? He says under the dash, but I couldn't find it... If I can dig it out, I'll install one of your bypass modules.
It's under the dash on the drivers side by the steering column. go in head first and stick your legs right up in the air. You'll see it

I flipped all upside down in the seat and took a good look under the dash.

However, I wasn't sure which of the plastic boxes was the module in question. Please take a look at the picture below. Can you point me toward the transmission memory box?
Electrical wiring Audio equipment Computer hardware Cable Automotive design

Sincere Thanks!
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I'm a little confused... The module on ebay doesn't look like the module shown in the video.

This is the module in the video. Single wiring harness connection, rectangular box:
Watch Hood Automotive lighting Motor vehicle Automotive tire

This is the one you linked to on ebay. Double harness connection with many wires, squarish-box:
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Ahh, I posted that on the wrong thread. That was for the gentleman in Jordan who has the seriph with the non start issue. @Jim Walters may be able to delete the post. I've deleted the content. The box from the video is correct.
Thanks. Do you see that box in the under-dash picture I posted?
I've looked all over under the dash for the module and can't find it. Is it possible my car doesn't have the same module as it's a 1993 model and yours is a 1997 model?
Here's an interesting article regarding the new module-controlled trans in the Brooklands starting in '92 May be worth looking into.
If your car has a 4L80E transmission, it will need some electronics to manage it. 6 minutes into this video, i have one in my hands.

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