80 series gearbox

[Tim Whiting]

Hullo Everyone, I have a 1994 80 series that has been "difficult " to change down from 3rd to 2nd for a while . Last week I had the gearbox, transfer case and clutch reconditioned. So excited when I picked the car up, only to be let down hard, 3rd to 2nd was pretty much exactly the same. Took it back, mechanic contacted the reconditioner, they told us to put in a lighter oil, so we did. It is better, but only because it was so bad before. My question is, can the 80 series box be smooth? aftermarket synchro? machining teeth? anything? All the other gears are fine. I'm aware this is a common prob for the good ol '80 series. I thought by now someone would have found a fix. Thanks

 

[Chris]

Welcome Tim. Great question. This is a common fault with the earlier boxes and something that Mr T did eventually get right. Personally I fixed it completely by simply buying a 100 series unit ha ha. But that's still sitting in my shed.

I have the same issue and so far have only managed to alleviate the symptoms by mixing 50/50 with oil and ATF. Sometimes it's prefect and other times it just won't go in. There are some people who have tried and some good experienced folk. So hopefully someone will be along soon with a more technical answer.

 

[Paddler Ed]

There may be a TSB from Toyota for a change in the gearbox oil - this was mentioned to me when I got my FZJ80 as the seller was ex-Toyota workshop... but he couldn't remember the change in specification, so that might be worth digging.

Toyota's do seem to be sensitive to gearbox oil - my 4Runner as the same, and the HJ45 is just getting to be troublesome, so I suspect it could do with new oil in it.

 

[chapel gate]

I would find out exactly what they term "reconditioned".

Giving it a clean and talking to it nicely won't make much difference.

Changing the synchro's and any other issues should make it shift like it did from the factory.

They are not over expensive, but if your paying labour on top it would be cheaper to buy a known good box. At least in the UK.

Years ago I started running red line MT 90. Made a huge difference in my gearbox.

 

[Chris]

I see that Roughtrax have started selling gear box internals now. But they're as much as a gearbox!

https://www.roughtrax4x4.com/toyota-4x4-parts/transmission.html

 

[AndycruiserguyLomas]

Toyota did have an issue with the 2nd gear synchro's during a certain period, I had one with only 80K miles (a 95) and the 3rd/2nd downchange always required a double de-clutch to facilitate a clean change. I had the box stripped and a new ( and expensive) 2nd gear synchro ring replaced. It was better but not great.
It seems that Toyota remedied this at the same time the 80 was badged "Amazon" with the twin airbag dash with a re designed 2nd gear gear hub and synchro ring which totally cured the problem. This hub/ring is not interchangeable with the earlier type though.
If you get a 2nd hand box get one from a 97-8 truck,. I have a 97 with 207Kmiles on and the gearbox is perfect.

You could try, like Chris, varying ratios of ATF in the oil. I have run 80 box's completely on ATF with a greatly improved 2nd gear change and no ill effects buts that for you to work out. If Mercedes manual box's use it for lubrication then it must do the job.

 

[bandsnbrakes]

Hullo Everyone, I have a 1994 80 series that has been "difficult " to change down from 3rd to 2nd for a while . Last week I had the gearbox, transfer case and clutch reconditioned. So excited when I picked the car up, only to be let down hard, 3rd to 2nd was pretty much exactly the same. Took it back, mechanic contacted the reconditioner, they told us to put in a lighter oil, so we did. It is better, but only because it was so bad before. My question is, can the 80 series box be smooth? aftermarket synchro? machining teeth? anything? All the other gears are fine. I'm aware this is a common prob for the good ol '80 series. I thought by now someone would have found a fix. Thanks

Did they lap the synchros? Change the mainshaft bearings. its all important.

 

[bandsnbrakes]

I see that Roughtrax have started selling gear box internals now. But they're as much as a gearbox!

https://www.roughtrax4x4.com/toyota-4x4-parts/transmission.html

Cheap really for what you are getting. try buying them from Toyota.

 

[Chris]

Sure, but add those together, put labour on top plus being without your 80 for a month and you'd be as well just ordering a new box direct from Mr T.

 

[frank rabbets]

I stripped my gearbox and coarse ground the syncro rings and hubs all with no effect. Now here's the clue. If you drain oil out of a box that the syncro has been working in you'll find it looks like diluted gold paint. That's because the syncro rings have been working. They wear out-that's how they work. My 80 oil has been completely like new on draining proving that the syncro rings have not been working. If it was a matter of just changing oil grades I think Toyota would have done that rather than changing internals.

I tried diluting my oil 50/50 oil and diesel with no improvement. I'm now running 15/40 engine oil with very little improvement.

 

[StarCruiser]

As an aside, I had a similar problem on my Mk1 Shogun. I stripped the box and replaced the synchros, put it all back and took it for a test drive. Not a jot of difference!!

 

[Tim Whiting]

Thanks everyone, I’m going back to the mechanic on Monday to ask some more questions. I’m not being unreasonable to pay $4,000 ozy dollars and expect a smooth gear change, am I ??. Thanks again for your responses and time

 

[frank rabbets]

The cause is a design fault, Tim, not a poor job on the recon.

 

[AndycruiserguyLomas]

Seconding Frank on this one, before I got onto the builder of the gearbox I'd experiment with the lubrication. Its a pity you didn't post this before you had the box rebuilt, the advice would have been to replace the box with a post 96 80 box or 100 series box.