Looking for 80 series transmission mechanic

Hi James

Just a thought, but what oil do you have in it? I changed the oil in mine once using a general 75-80 gearbox oil and it would not down shift without crunching. I replaced it with Mobil 424 and it was like I'd fitted a new gear box. It might be worth trying a different oil.

Jon

Hi James
Your right synchro are stuffed.common problem.
Can't recommend a good mechanic.
A lot of people just learn to live with it.
try castrol VMX-M GEAR OIL
Or Redline MT-90 full synthetic $25 quart.
What i have read is that the original synchros are too short.
Terrain tammer make longer ones to fix it.for longer.

My synchros aren't the best either, i am using full synthetic oil.
and when changing gear leave the clutch pedal in but just pull the gear lever in to neutral then just take the weight of the lever momentary and pause then pull it or into the next gear and it goes smoothly similar to the old double shuffle.

Also factor in a new clutch rear engine seal if the gear box is to come out.

Rob.

What make a 80 series trans so special?

It's still only an everyday gearbox and rebuilding gearboxes isn't rocket science.

Sorry I can't help you as I don't know any one who just specialises in that trans.

So 80 series are special!

It wouldn't matter if you opted for an exchange unit or had yours rebuilt as they will split the transfer case from the gearbox and then bolt the transfer case back up to the reco box. You will still end up with your part time system.
I would try changing the oil to the already stated Mobil 424 or the Caltex Textran which is the same oil. Makes an unbelievable difference to the shifting. Can also use this oil in front wheel drive gearbox's that are starting to get old. It is in my sisters Toyota Corolla that is still original after 420 000 km. The gearbox is a bit loose but changes with no crunches.
Scott

Gday
Try ..Stewart 97631911..

Hi James,
As you have nulon to get rid of you will need to do another oil change after about 1000km and do it when it is hot to flush out the left over nulon. Nulon is awsome in everything except syncros as it is too slippery stopping the syncros from slowing down to do what they are supposed to.
My 80 has 410,000km on the original box and clutch and will crunch if I try to shift too quickly. Drive it like a truck not a sports car and you will be ok. I only ever use the Castrol VMX, but after 3 quick changes to flush out all the mineral oil then the redline is supposed to give superior results but at the price i'll stick to the castrol as it is available anywhere.

Oils ain't oils ... or something like that. These top 3 are all API rating GL4.

It's a pitty I couldn't put a table in here and it automatically removes multiple spaces.

Product,Grade,Visc@40C,Visc@100C,ViscIndex,PourPoint
Mobil Mobilfluid 424,80W,55,9.3,145, -42C
Castrol VMX80,75W/80W,59.2,10.5,160,-32C
Caltex Textran THD,?,57.5,9.5,148,-39C
for comparison an auto trans oil ...
Mobil 1 Synthetic ATF,?,34,7.6,199,-54C
and a standard gear oil ...
Mobil XHP 75W-90,75W-90,100,15.5,165, -45C

By the way Mobilfluid 424 and Mobil Agri Fluid 424 have exactly the same specs.

So what does this all mean? The Grade is an easy way of showing the oil's characteristics but each rating covers a certain range so is not particularly useful if you want to know the specifics. Vicosity at 40 degrees and 100 degrees are self explanatory and the Viscosity Index is basically a rating of how much the viscosity of the oil changes between 37.8C and 98.9C with a higher value being more stable. The Pour Point is the lowest temperature the oil will pour.

I suppose Mobilefluid 424 is slightly better of the ones discussed if we want to try a non-standard oil because of its lower viscosity.

Stay tuned for some oil changing shannanigans.