Autobox/ Speedo link?? Problem

[adrian]

Today when i was driving my Isuzu Bighorn 1994 3.1 TD Auto back from work, i managed to do about 30miles (50km) on the motorway, when the car seamed to develop a "misfire" .

But the tacho and speedo were "twitching" together with the misfire.

It was quite a pronounced misfire, giving it more gas seamed to make it worse.
(looking back and thinking about it, it could be the auto box selecting that semi-neutral thing it does when it changes gear)

I managed to get to the services, for some food, and upon recommencing my journey, the problem seamer to clear.

Then it returned, but more violently,
the only was to relieve the problem was to hit the overdrive button, and proceed in 3rd gear.

i did maybe another 50km then the speedo gave massive under-read, (showing 50kmh but gps speedo showed 80kmh)

then the speedo died and dropped to zero.
at the traffic lights in town the speedo did some wild deflections
upto 120/130kmh, then died again (i was stationary)

I noticed the "CHECK TRANS" light was intermittently flashing. It would flash for 10 or so seconds, then not flash for while, the "A/T TEMP" light on the dash was not lit.

Is there anyone else who has encountered this problem?

Could it be the speedo sensor on the gearbox?

Maybe the transmission oil needing change??

Or possibly an electrical fault somewhere, as i know there is something that stops the overdrive gear from coming in before 40mph, and believe this is on the speedo itself.

I hope it isnt the transmission itself that could be the cause
as here in the UK it would cost more to fix that than the car is worth!

I hope you guys are able to help

Take care

Adrian

[adrian]

I did think the other day that the speedo drive comes from the transfer box,
and not as i origionally thought from the gearbox.
but i still hope it is a small electrical gremlin that i can solve with a sensor.
adrian

[geeves]

Is the speedo on these electronic or cable?

[adrian]

Its an electronic speedo.

[adrian]

Have just spoke with a company that deal specifically with spare parts for Japanese import cars here in the uk.
I was informed that there is a magnetic speed sensor on the drivetrain
I am unclear if it is on the propshaft or on the transfer box,
but was informed that it is common for these to fail (my bighorn has done 240,000km)
so i ordered one, (AU$250+tax) so i am hoping that this will cure the problem.

I will let you guys know if this part fixes the problem.

adrian

[adrian]

Guys sorted out the problem, it was the speedo sensor on the side of the transfer box,
there are 3 different types fitted acording to the supplier.
'jobs a good-un!'

ade