Thread: Too Much Grunt

Originally Posted by Bush65

The LT77 started out from an early Jaguar 4 speed. 5th gear (overdrive ratio) was added in an extension housing behind the main gear case.

Was redesigned to produce the R380, which has 5th (overdrive ratio) and reverse in an extension housing behind the main gear case.

The suffix J (serial No) R380 have a bad stress raiser in the main shaft, which often leads to a broken shaft. This was fixed in the suffix K version which came out in 1999.

I have an Isuzu MXA-6R six speed box behind a 4BD1-T, and both 5th and 6th are overdrive ratios.

Below are the various Rover gear ratios.

Main Gearbox Ratios
Gearbox 1st 2nd 3rd 4th 5th Rev
LT77 early 90/110 3.585 2.3008 1.5074 1 0.8314 3.7007
LT77 V8 Disco/90/110 3.321 2.132 1.397 1 0.77 3.429
LT77 200TDI Disco/90/110 3.692 2.132 1.397 1 0.77 3.429
R380 V8 3.321 2.132 1.397 1 0.732 3.429
R380 300TDI/TD5 3.692 2.132 1.397 1 0.77 3.429
LT85 90/110 3.6497 2.1804 1.4362 1 0.7951 3.8242
LT95 RRC/101/110 4.0691 2.448 1.5049 1 3.6643
ZF4HP22 Auto 2.48 1.48 1 0.728 2.086
TorqueFlight TF727 Auto 2.45 1.45 1 2.2
Series II 3 2.043 1.38 1 3.02
Series IIA 3 2.22 1.5 1 3.02
Series III 3.68 2.22 1.5 1 4.01

Transfer Box Ratios
T/case High Low
Series I, II, IIA 1.148 2.89
Series III 1.148 2.35
Series IIA 109, 6 cylinder 1.53 2.35
Series 1 Ton 1.53 3.27
Series 109 FC 1.53 2.92
LT95 RRC 1.113 3.3206
LT95 101 1.174 3.3206
LT95 110 1.3362 3.3206
LT230 Discovery/RRC 1.222 3.32
LT230 V8 90 LT85 1.192 3.32
LT230 90/110 1.41 3.32
LT230 110 1.667 3.32
LT230 TF727 1.003 3.32
Ashcrofts Low Ratio LT230 1.222 5.95 (no longer available and few were made)
Maxi-Drive Low Ratio Gear Set 4.340

A couple of minor corrections/additions

LT95 110 with 4BD1 or 4BD1T, Transfer high range is 0.996:1
According to my information Series gearboxes
Up to 2a suffix B
1 2 3 4 R
2.996 2.043 1.377 1.0 2.547

From Suffix C (Series 3 the same)
3.68 2.22 1.5 1.0

Transfer Case
Up to 2a Suffix B
1.148 2.888

From 2a Suffix C
1.148 2.4
Six cylinder the same as four cylinder, both 2a and 3, but the transfer case fitted to the One Ton was 1.53 3.27

The above information is from the relevant owner's manuals.
John

Originally Posted by BigJon

Trev - IMHO, you are asking for trouble. We recently replaced a TD5 Defender gearbox which had lunched fifth gear in a major way due to similar towing techniques (tandem axle trailer with a canvas box). This vehicle is regularly maintained (10 000km service interval, all oils replaced as required) and had done only 125 000km.

OK. Been thinking about this even more. Drove down the road at 100klm/hr in 4th! 4,200 rpm. Ain,t no way I,m towing to Darwin at those revs.
This tends to indicate that 5 speeds are intended for the gear box. Max power std is 1950 revs, mine chipped is 2800 revs. So why would you drive at 4000 revs? If fourth was say 3000 revs for 100klm/hr and fifth was 2500 revs, I would tend to agree its purpose, (5th gear), or description of it would be an overdrive gear. Just my thoughts.
The gap is too big to make any sense to call it overdrive.

Trev.

Originally Posted by JDNSW

A couple of minor corrections/additions

LT95 110 with 4BD1 or 4BD1T, Transfer high range is 0.996:1
According to my information Series gearboxes
Up to 2a suffix B
1 2 3 4 R
2.996 2.043 1.377 1.0 2.547

From Suffix C (Series 3 the same)
3.68 2.22 1.5 1.0

Transfer Case
Up to 2a Suffix B
1.148 2.888

From 2a Suffix C
1.148 2.4
Six cylinder the same as four cylinder, both 2a and 3, but the transfer case fitted to the One Ton was 1.53 3.27

The above information is from the relevant owner's manuals.
John

Also, LT230 with 1.003:1 ratio fitted to all 5-speed (LT85) 110s with ISUZU 4BD1.

Originally Posted by Bush65

I have an Isuzu MXA-6R six speed box behind a 4BD1-T, and both 5th and 6th are overdrive ratios.

What transfer case are you running and what vehicle is it in?

Originally Posted by BigJon

What transfer case are you running and what vehicle is it in?

T/case is Atlas 5:1, in a bushie.

so fourth in the r380 is 1-1

so this is just running on the main shaft straight through the box, no gears????

serg

Originally Posted by uninformed

so fourth in the r380 is 1-1

so this is just running on the main shaft straight through the box, no gears????

serg

That is correct.

Trev, I always use fifth when towing in the 'fender, (196,000km and spent the first 76,000 being flogged by the BFC up around Big Jon's turf) as does the SO in her Patrol, (216,000km) and we've all heard the horror stories about GU's and fifth gear...
(OK, they were only caused by an incorrectly machined shaft)