Thread: Santana gearbox (LT85) question...

Howdy,
A few years back I had an Isuzu county with the Lt85 Santana box.
It is effectively a four speed box with a 5th gear overdrive built onto the back of it in a small additional housing.
The weak link is a Pi#sy circlip on the mainshaft which locates a gear driving the 5th
( ask me how I know!!)
I was cruising over the sandhills in 5th gear on the Oodnadatta track and yacking away to the passengers and let the revs drop and the engine slog without changing down to 4th going over a rise...my driver error.
Of course the Isuzu engine handles such torque but the weakest link is in the Box.
The resulting stress /shudder snaps the circlip and the gear moves back on the output shaft. this allows the small springs and Detents ( locating pins) to fall to the bottom of the 5th gear housing...hence no 5th gear.
A workshop diagram on the LT85 shows what I mean.

I drained/strained the oil and checked that no bits were jammed and easily( but carefully) drove from Oodnadatta to Aice Springs with a 4 speed box.

I bought the circlip at the dealer in Alice and repaired it ....not too difficult, even without my workshop facilities...but of course you need to remove the transfer case to get the gearbox out....and so you remove the tailshaft; floor etc etc..That's what makes it a big job. From memory I did not have to pull the main box apart..just the 5th gear housing on the back.( this is of course between the box and the transfer case!)
Then you start replacing input/output oil seals etc... whilst you have access.
I was able to re-use the detents and springs ( sitting in the bottom of the 5th housing).
The cirlip is pathetic!!! about 1/4 of the size/strength of a similar item in a 60 series toyota...it looks like an afterthought.. from an engineering point of view.

From then on I carried spare springs, detents and that circlip!!

In summary, I reckon the LT85 is a bit lightweight.. but you need a 5th gear.
5th is too "tall" for a headwind... and you will gradually lose road speed.
Just remember to change back to 4th .

Cheers
Bob

Originally Posted by DeeJay

I'm in the process of swapping out a lt85 for a lt95 in an isuzu. I'll be posting it up under projects & tutorials in the next few weeks.
But whoever buys it is going to miss having the 5th gear.....

The o/d fifth absolutely makes the County-Isuzu as a touring car. 2000 rpm @ 100k's and 2200 rpm at 110 k's. I don't use o/d under 80 k's and shift down to 4th when the engine starts to slow on hills. Mine is a normal 4BD1 with 430,000 k's on it.