The 3 Speed GM180 Automatic Transmission and the 5 Speed LT77 Manual Gearbox were fitted to the automatic and manual versions of the Series II Rover SD1. In both cases they are considered to be very robust units providing routine maintenance guidelines are observed.
Unfortunately as the age of our cars increased and ownership began to fall into the hands of enthusiasts not seeking dealership servicing, like all mechanical components they start to give problems if maintenance is overlooked.
During my ownership of four Rover SD1's I have come across a number of routine and difficult fault situations that needed solutions. It’s fair to say that most elements of this essay are the result of original thought (not to say other people hadn’t thought of them too) but I had not previously come across them.
Frequently we are reminded - "Top up the gearbox". It's easy to say, isn't it? Not so frequently we are reminded - "Drain the gearbox ---, etc" and don’t they both fill your head with dark thoughts?
Here then are some ideas to make things easier and few other snippets I have come up with, including a really radical treatment for a badly behaved 5 Speed LT77 Manual Gearbox. Read or download the PDF from here: (36kb)
Rover SD1 GM180 Automatic and LT77 Manual Gearbox Solutions
Click Here to Read or Download the PDF Article (or the below links)
Rover SD1 LT77 Manual Gearbox Remote
Modulator Valve for GM180 Transmission
64 Vacuum modulator and oil seal
65 Push rod
66 Modulator valve
67 Modulator Sleeve
In the above mentioned "Gearbox Solutions" PDF is a section related to my personal practice of using Mobil 1 or Castrol RS combined with Molyslip Gearbox treatment as the replacement Gearbox Lubricant for the Manual LT77 gearbox.
It has worked splendidly for me since 1996, but recently there is quite a lot of interest in Redline MTL, specifically formulated for this type of gearbox. It's got to be worth a try, I reckon.
The Redline MTL Technical Information leaflet can be printed off, double-sided, onto an A4 sheet and you get a handy three fold leaflet. here: (40kb)
Rover LT77 Gearbox - Workshop Manuals
Typically, Rover SD1's sport the LT77 5 Speed gearbox in various forms. Late Vitesses, for example, had an uprated version. Rover SD1 Workshop manuals variously present service instructions and should be the definitive source of data. For further information here are two PDF's of service instructions for Landy/Defender applications to add to the sum of general knowledge.
Land Rover 4 and 5 speed LT77 Gearbox Workshop Manual, PDF format, here: (2.0mb)
Rover Defender 5 speed LT77 Gearbox Workshop Manual Supplement, PDF format here: (1.9mb)
LT77 Speed Transducer Repair
This image shows an LT77 Gearbox Speed Tranducer after it has been repaired. Read all about how to do this from here: