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defender9



Member Since: 12 Mar 2016
Location: Fylde Coast
Posts: 1611

United Kingdom 2015 Defender 90 Puma 2.2 SW Keswick Green
LT77 gearbox differences
I have acquired an LT77 gearbox Suffix H for a project. I understand that the Suffix H boxes were the last and strongest LR made. Could someone who is knowledgeable about these boxes let me know what the difference is between say Suffix D,E, F boxes and a Suffix H.
Is it bigger gears, shafts , bearings and if so which ones?

Many thanks in advance
Post #817411 28th Feb 2020 4:32pm
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gilarion



Member Since: 05 Dec 2013
Location: Wales
Posts: 5084

Wales 2007 Defender 90 Other CSW Trident Green
There have been only two versions of the LT77 gearbox though during the manufacturer a few refinements were introduced (see the last paragraph) Your gearbox suffix H only means it was manufactured in 1994

The LT77 is an updated version of an old Jaguar gearbox that found its way into current model British cars manufactured by British Leyland. Yes the distance between the main and lay shafts is 77 mm. There were two versions of this gearbox. The earlier version is known as the short stick version. The later version was introduced around 1988 is known as the long stick version.

1991 through 1993 The LT77S was introduced to the Defender V8 line and all models using the Tdi engine as an interim replacement for the no longer available LT85. The LT77S was a strengthened version of the LT77. The 'S' on the LT77S stands for 'Synchromesh'...it was modified for a 'smoother gear change'. The bell housings and input shafts of the LT77S differ between the V8 and Tdi due to Tdi's more aft location.

If your serial number starts with 50A 51A 56A 58A 60A 61A 66A 68A 73A you have a long stick version
if your serial number starts with 53A 55A 63A 67A 69A 73A you have the short stick version.

LT77 Development

The LT77 was introduced to the Landrover range in approx 1983 with the suffix 'D' box and was developed over the years to the suffix 'H' which was last used in 1994.

The 'D' and 'E' are very similar the only difference being the reverse gear was a little fatter in the E,

When they went from 'E' to 'F' larger layshaft bearings were used.

The 'G' was further improved by all the gear teeth including the pinion getting approx 20% thicker. Also, a much wider pump was used to increase the lubrication and cope with the fact that some of the LT77's were now being supplied oil cooled, ie V8 NAS 90, 3.9 RR Classic and the 3.5 EFI Discos.

The 'H' (termed the LT 77S) was the same as the 'G' in terms of strength but used a different synchro set up called the'Double Synchro', In reality it didn't work much better. For those who like Welsh Mountains and narrow boats have a look at my videos and photos at..

http://www.youtube.com/user/conwy1
Post #817415 28th Feb 2020 4:49pm
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diesel_jim



Member Since: 13 Oct 2008
Location: hiding
Posts: 6026

United Kingdom 2006 Defender 110 Td5 SW Epsom Green
55A I meant 56A was also the military version with lowered ratio (or is it higher in numerical value) 1st & 2nd gears to help the asthmatic 2.5 NAD pull anything heavier than a 9x9 tent
Post #817435 28th Feb 2020 6:50pm
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