HZJ 79 gearbox

[Ratfarmer3000]

Hey guys, I’m new here.
I bought a Hzj79 2003 1hz with an aftermarket turbo. I’m fairly simple when it comes to working mechanically but I’m keen to learn. The Ute has 250xxxkms and I’m having issues with the gear box. It’s crunching when going into second although if I shift with care it seems to go in alright.
I’ve been doing some reading am and starting to think changing the transmission oil could help. Nulon recommends GL5 but I’ve read some people saying GL4 is best for a struggling gearbox.
Any suggestions ?
Thanks

 

[Franglais]

A couple of general comments first:

As I understand it (subject to correction) the additives in GL4 and GL5 are different, and will affect the wear in gearboxes.
If your gear box has already suffered wear related damage then changing oils won`t make much difference now.

If the synchro is worn then the only remedy is to go inside the box to inspect and replace parts as necessary.
Dropping a heavy transmission is not an easy job. Going inside a gearbox in a home workshop is again beyond most. Many pro garages will drop a box but send it to a specialist for any repair necessary.
Sure, many "get away with it" but the potential for dropping the box, twisting shafts, doing even more expensive damage is high. Not for debutantes.

Having said all that, Don`t Panic!
I would firstly check the oil levels in both gearbox and transfer box. These vehicles do seem to have issues here.
I would then drop the oil out of the gearbox. Check it`s colour and look for shiny bits in it. There will likely be a bit of sludge in there, as the synchro wears into fine dust that is almost held in suspension. More than a very few shiny steel bits shouldn`t be present though.

Worn synchro is something I probably live with.
Change the oil, keep an eye on the levels frequently until you are confident all is well, and just get used to the character of your vehicle.


Edit to add.
This looks like an interesting article on transmission oils. More than a minute coffee break read!

https://www.widman.biz/uploads/Transaxle_oil.pdf