Yet another LT77 question

V8chevette · Post by **V8chevette** » Sun Jun 20, 2010 10:13 am

Hi all, just a quick question regarding the LT77 box.

Which boxes have the 0.77 ratio fith gear? i'm looking for one as i need to get the revs down at motorway speeds as i'm running a 3.9 diff in the rear end.

Any serial numbers i can look out for?

Thanks in advance

v8granada · Post by **v8granada** » Mon Jun 21, 2010 8:38 pm

Extract from this site: http://www.roversd1.co.uk/tech_data3.htm

All models of the SD1 are fitted with the same ratio 5 speed
box (with some exceptions, see notes below) The bell housing
will be different for each engine type as well as axle ratio's.

Gear ratio's 5 speed series 2. all models 5th 0.792:1
(Series 1, 5th Gear: 0.833:1) *see note.
2400SD see note**

4th 1.000:1 All other ratio's as listed.
3rd 1.396:1
2nd 2.087:1
1st 3.321:1
Rev 3.428:1

*Note: Later series 1, cars have series 2, ratio's i.e. 5th gear ratio. ** 2400SD Diesel 5th gear ratio 0.77:1, Axle ratio 3.9:1, no auto option. The Vitesse and VDP EFi have the same ratio's, but are uprated to cope with the higher powered engines. Having shot-peened gears, and stronger bearings.

Looks like the only one with the 0.77 ratio is from a 2400SD, that's not to say that ratio wasn't fitted in another BL motor - Sherpa, Triumph, Land Rover etc.
The best ones to go for are the later C or D suffix boxes as they are stronger "allegedly"

Hope this helps, Steve.

DaveEFI · Post by **DaveEFI** » Mon Jun 21, 2010 10:43 pm

In theory the EFI was auto only. Although it's said one or two may have been manual to special order. The auto, of course, has the 2.85 rear axle, as has the Vitesse auto.

conrod · Post by **conrod** » Wed Jun 23, 2010 4:44 am

got the LT77 box out of my 1995 LDV 400 at the moment to replace the clutch. Marked up the input/output shafts, looks like 5th is 0.77 on mine according to the eyecrometer! Shorter than 0.75,(3 turns of input shaft gives just under 4 turns of output) but taller than 0.8 (8 turns of input shaft gives just over 10 turns of output) so must be 0.77.

Conrad

PS. the serial number of mine starts 35A....

PPS. you think you got problems with a 3.9 axle ratio? Mine is a 4.89!

conrod · Post by **conrod** » Fri Jun 25, 2010 9:43 pm

Just found this in the many bits and pieces I had saved:

bodger · Post by **bodger** » Fri Jun 25, 2010 11:46 pm

Hi conrod ...

the box in the LDV 400 is a R5-150 , and although it look like an LT77 ..the primary ratios are differant along with all the ratios and the front and rear bearings ..

the LT77 box fitted to the SD1 had a similar type to the TR7 box's and the vitesse had a differant higher 5th gear ratio

INFO FROM A WHILE BACK :

with the gearbox stripped and the clusters in situe ie:the input shaft pointing sky ward
working from the top

input ............. layshaft

22 ............. 33 = 4th / pinion gear
27 ............. 29 = 3rd
32 ............. 23 = 2nd
reverse .............
31 ............. 14 = 1st
20 .............. 36 = 5th
and 5th gear below the plate

it has the same ratios as an SD1 V8 box

to calculate the ratio's ..first divide the pinion gear ie: 33 / 22 =1.5
then divide the input shaft by the layshaft and multiply by the 1.5 ..and thats the ratio
ie:
1st gear
31 divided by 14 = 2.21 then times the 1.5 you got earlier and the result is 3.32 which is right

conrod · Post by **conrod** » Sat Jun 26, 2010 1:37 am

thanks Bodger,
I just noticed it describes the gearbox as an R5-150 at the top of that info sheet I posted - dohh! Do you think this is a stronger box than the LT77, or just different ratios?

Conrad