Isuzu Trooper Owners Club UK™

IanP · ** Joined: 13 Jun 2005 Posts: 100 Location: North East

Had the usual gearchange problems since buying my truck 1 1/2 years ago. Changed the oil last year which improved things for a while, but it was soon back to its old tricks of changing gear when I least expected it. Anyway, bit the bullet today and took the gearbox suction filter off for a clean. As I couldnt clean it properly, I decided to take it apart, which is a bit tricky. Although the mesh didnt look bad, it is really fine and I think that the slight contamination I found makes a big difference. Took it for a good run, and at last the box is working the way I thought it should, gear changes are now nearly imperceptible, and it will hang onto overdrive at 70 mph up motorway inclines without dropping straight down 2 gears. Truck is a 3.1TD, jap import when I bought it, now got 96000km on it, so if anyone else has this problem, might be a good idea to have a look at this filter

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siweb · ******* Joined: 18 Apr 2004 Posts: 1590

I was looking at the filter the other week when I change my oil and it didn't look like it would come apart as the sides where folded and crimped around each other. how you manage to undo it?
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IanP · ** Joined: 13 Jun 2005 Posts: 100 Location: North East

I eased up the crimped edges with a small flat blade screwdriver until i could pull the filter apart. The mesh is caught between the two covers, on a support frame and it can be removed from that for cleaning. Just washing it wasnt sufficient to budge the deposits, they needed to be gently brushed off at the same time. I would be very careful with the mesh as it appears to be very easliy damaged. After reassembling, the edges can just be crimped again with pliers.

Hard1 · Posted: Mon Aug 21, 2006 15:00 Post subject:

Well done Ian - all the Bighorn boxes I've ever come across have also acted in a strange arbitary manner including involuntary shifting and there have been a number of "fixes" over the years including changing oil, shortening shifter cables, changing speed sensors and chanting mantras during the Winter Solstice, but none seems to have worked. I would like to see if another member has the same success using your method before I try it though. I've got kinda used to it's strange ways but when it changes down going up a long hill when it doesn't need to , Grrrrrrr Evil or Very Mad

that really gets my goat!!!!
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1999 Cougar with a NICE motor..

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IanP · ** Joined: 13 Jun 2005 Posts: 100 Location: North East

Still working OK, and hanging onto overdrive up long motorway inclines. Fuel consumption improved as well, now up to 26 mpg from 22 mpg Shocked

markymoan · Posted: Thu Aug 24, 2006 9:32 Post subject:

Thats great Ian, so theres no excuse for you not to say hello at the meet this weekend Wink

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IanP · ** Joined: 13 Jun 2005 Posts: 100 Location: North East

MarcusQ · Newbie Joined: 04 Sep 2006 Posts: 4 Location: Coventry

This involuntary down shift sounds like the problem I have. For the novice could you explain how to get to the gearbox suction filter!

Hard1 · Posted: Mon Sep 04, 2006 19:37 Post subject:

Well, I think you have to drop the transmission oil pan off the box to drain the oil when (if) you change it. Most people just crack the bolts to let it drain (it doesn't get it all out if you do it this way). Take the pan right off and then the filter will be exposed. Then I presume you proceed carefully as detailed above!
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1999 Cougar with a NICE motor..

Click HERE to see under my bonnet!

MarcusQ · Newbie Joined: 04 Sep 2006 Posts: 4 Location: Coventry

Thanks for that i'll give it a go. For info I think I have two problems, the first as described (downshift when overtaking or going uphill too early or random) the second when damp no 4 gear. The reason I mention this is that this seems to be a very common story with the 3.1TD Auto. Would it be worth doing a "sticky" common gearbox fault finding guide (I can start the ball rolling with what I find out testing, wire colour codes etc). Looking at the other posts there is a huge amount of info relating to auto gearbox problems, but its difficult to collate.

The main offenders (options to fix most problems) seem to be:

Speedo
Gearbox speed sensor
Temp sensor
Throttle sensor (on fuel pump)
Gearbox oil strainer

If I can work out anything inteligble i'll post, but thoughts from the far more experienced appreciated. Apologies if it's already there but i'm new to the site.

The other question is that is there any way to simplify the sensor arrangement on the Trooper / Bighorn. I'm sure it was great when the trucks were new but 12 years down the line the complex electronics are a bit of a pain?

Hard1 · Posted: Mon Sep 04, 2006 22:56 Post subject: Bighorn Auto Greabox Problems?

The biggest "problem" isn't really a problem at all; the apparent random or sensitive shifting of the box. They all do it to varying degrees. Many on here, including myself, treat this not so much as a fault as an "eccentricity" and learn to drive around it. The main recurring "fault" (and that doesn't happen very often) is the failure of the speed sensor which controls the speedo and may result in erratic shifting but not always.

Your "no 4th gear when damp" is a bit of a strange one considering there is no 4th gear on my auto Bighorn so cannot comment. I have 3 gears (D, 2, L) a locking torque converter and an overdrive which works on 3rd (top) gear (D). This is operated by a switch on the gearlever, and doesn't work until the engine is warm (designed operation not a fault) . When operating normally, the gearbox changes up twice after top (3rd) gear as if there are 2 extra gears now making 5 - are you following this?) . I suspect most members Bighorns will be similar. Strangely, the owners manual for Bighorn (1990-1995) specifically mentions 4 gears (D,3,2 & L) but I've never seen one with this arrangement.

It could be a Grade Option perhaps? Maybe other members could comment on this...

There are no "complex electronics" on the 3.1tdi and therein lies it's main strength plus there are but a few simple fault codes. One further solution to erratic shifting has been posted by IanP and it works for him but no-one else has tried this yet so (with due respect to Ian) the jury is still out until we have a consensus. It may have solved a problem for him, but I think we need more reports on his method. I won't be bothering because I have learned to drive around any "problem", and it isn't really a problem. It is just different from any other auto I've driven.

There is no throttle sensor on the pump - it's a mechanical link, which, if too tight can cause early shifting (it should be slack with closed throttle. If it is tight then adjust it). Temperature sensor? Never heard of that one either...

Of course these sensors may well be on the much later Bighorns (97-2000?) but don't appear on the '92-'96 models as far as I'm aware and I'm not sure I've seen or heard of any imports later than '96, unless you know different....

.Always happy to learn though.... Very Happy

You might also want to let us know what year your vehicle is....
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1999 Cougar with a NICE motor..

Click HERE to see under my bonnet!

Grandad · ******* Joined: 22 Sep 2005 Posts: 1902 Location: NORFOLK

in the middle of 1995 3.1td automatic bighorns became drive by wire with a fully electronic injection pump and ecu controlled engine and gearbox

Hard1 · Posted: Mon Sep 04, 2006 23:07 Post subject:

Aha!

Greetings and thanx Grandad. Two very different animals then...did they also change to 4 speed?
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1999 Cougar with a NICE motor..

Click HERE to see under my bonnet!

siweb · ******* Joined: 18 Apr 2004 Posts: 1590

That is 2 ECU's one for the engine and one for the gearbox. mine is a 97 bighorn and has a major electronic fault.
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Hard1 · Posted: Mon Sep 04, 2006 23:18 Post subject:

Hmm, am beginning to appreciate the "robustness" of the simple early models.

Thing that gets me about all modern diesels is that they start off with something virtually unstoppable (diesel engine) and then make it inherently unreliable (electronics and fancy injection systems). True they get better mileage, but at what ultimate cost? Confused

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1999 Cougar with a NICE motor..

Click HERE to see under my bonnet!