KZJ78 Overdrive switch solenoid? overdrive not engaging.

[graysworld]

Does the switch on the gear stick operate a solenoid which in turn operates a solenoid in the gearbox to engage overdrive? While waiting for a filter I am trying to find other reasons for the overdrive not working. The overdrive on/off light is working. I have had some capacitors in the ECU replaced. It has new oil but I have yet to change the filter. Any suggestions? A343F Gearbox.

Graeme

 

[CRSWA]

Does the switch on the gear stick operate a solenoid which in turn operates a solenoid in the gearbox to engage overdrive? While waiting for a filter I am trying to find other reasons for the overdrive not working. The overdrive on/off light is working. I have had some capacitors in the ECU replaced. It has new oil but I have yet to change the filter. Any suggestions? A343F Gearbox.

Graeme

You may have a bad solenoid. Mine went bad a few months ago. If you're going to change the filter anyway, it's easy enough to swap in new solenoids. Here's a kit that has everything you need:

A343f Shifting Issues

forum.ih8mud.com

 

[graysworld]

Thank you....I am having problems with the link. Would you be able to post an exact link for me please.

Graeme

 

[CRSWA]

I just checked and they're not available anymore. I didn't see any comparable kits on Amazon.

The key to this, at least in the States, is that the same basic transmission was used for Jeeps of the same era, so if you can't find what you're looking for under A343f, you can search the Jeep A340 transmission kits. Just make sure the years match because these transmissions changed a bit over time.

 

[graysworld]

Thanks, found this one Solenoid Service Kit Toyota A340 Transmission 1985-1994 4WD | eBay - https://www.ebay.co.uk/itm/194073307352
but seems to be missing the gasket for the filter. I have messaged the seller to see if it is included. No big deal I can get the gasket elsewhere or hopefully use the old one?

Graeme

 

[AirheadNut]

That looks like it should work fine. You could probably get the filter gasket somewhere like partsouq.

 

[graysworld]

Thank you for all your replies I will keep you updated.

Regards Graeme

 

[graysworld]

Well, we live and learn or hope to. The reason the overdrive was not working was because the 4wd was engaged! I did not notice, not helped by no warning light on the dash…poor excuse for a schoolboy error!

Anyway, thinking I needed new solenoids and filter kit I have found these on Ebay.

3533660010 Genuine Toyota GASKET, OIL STRAINER SPACER 35336-60010 | eBay - https://www.ebay.co.uk/itm/183887144535 Gasket

Solenoid Service Kit Toyota A340 Transmission 1985-1994 4WD | eBay - https://www.ebay.co.uk/itm/194073307352 Filter and solenoid kit.

One from USA and one from Parts Souq via Ebay. So not all lost and helpful for future. I may even change the filter anyway as it is a serviceable item. Although I have worked on vehicles all my life, I have never owed a vehicle with an automatic gearbox, so it is all new to me!

So, thanks to everyone for advice
Regards Graeme

 

[garethXL]

Interesting story, I was experiencing exactly the same problem with my KZJ78 - its been in storage for around 6 months and I got it out today - started first time and ran wonderfully of course but I noticed on the local A road that the overdrive wasn't kicking in. Tried various combinations of o/d off/on, ECT power, stopping and starting the engine etc and finally resigned myself to the idea that there may be a dead capacitor in the ECU.

I got home and tried a google search firstly to check the location of the ECU and secondly to work out what to look for - and after reading this post it turned out I had knocked in the 4WD button with my knee - manual hubs so really I'm not sure if the 4WD button even does anything... Thanks! Overdrive now working as normal!

***Plot twist***

My KZJ78 is in fact the very same vehicle from the original post by Graeme

 

[Tigris]

Interesting story, I was experiencing exactly the same problem with my KZJ78 - its been in storage for around 6 months and I got it out today - started first time and ran wonderfully of course but I noticed on the local A road that the overdrive wasn't kicking in. Tried various combinations of o/d ofhttps://on, ECT power, stopping and starting the engine etc and finally resigned myself to the idea that there may be a dead capacitor in the ECU.

I got home and tried a google search firstly to check the location of the ECU and secondly to work out what to look for - and after reading this post it turned out I had knocked in the 4WD button with my knee - manual hubs so really I'm not sure if the 4WD button even does anything... Thanks! Overdrive now working as normal!

***Plot twist***

My KZJ78 is in fact the very same vehicle from the original post by Graeme

Hey there...

Been there. Mine was caused by the ECU.

In the course of pinpointing the culprit, I replaced the three shift solenoids and transmission filter, and did a complete ATF flush. These measures helped but the dreaded capacitors' plague was ultimately the cause of my shift anomalies.

I did three writeups on the repairs/maintenance items above.
Here,
here, and here.

Glad it was a simple button bump and not an actual fault like mine was. That being said, replacing the capacitors preventatively is really worth it in order to avoid dealing with a damaged pcb. My 2 cents.
Cheers

Moe