gearbox & transfer oil

[1logger]

hi all i suspect this will be sorted very quick.

gearbox & transfer oil grade ?? I used caltex 20/40 for both refill not top up .

But it seems that the gear box is not entirely happy gears are very sticky mostly 2cnd & 3rd .

comments and ideas appreciated

thanks
jeff

[mudgrip4]

Can only comment for my 4jb1T, but most motor oils don't work for my gearbox as appears the additives defeat synchro action. Tried 10w30 and 15-40 years ago but resulted in stiff gear action.

Two main options: after discussing this with clubmates with isuzus, found they use auto trans oil in their gearboxes. Tried this last 2-3 years and its fine - first 1-2 gearchanges 1st to 2nd a little stiff when cold but then great. Others on this site also recommend buying cheap grade engine oil from warehouse etc - $8-10 for 5 litres sort of thing, and use this successfully as it doesn't have the additives in it that more expensive product has.

Re transfer case I've always used 90 grade gear oil and this works fine - though the Isuzu manual might in fact recommend engine oil (15-40) in t/case as well - someone else will know this.

Mike

[1logger]

hey Mike

the eng oil i got was from the warehouse and cheap to I suspected that the good oil would play with the syncro so avoided it .

interesting the auto trans fluid will keep that in mind and just hope that its just the shock of new oil.

transfer : you recon 90 grade works ok in yours that to will be kept in mind .

thanks
jeff

[nig]

Looking in my TFseries workshop manual, the recomendation for geabox oil is 5W-30 if ambient temperature is below 32degreesC. and SAE40 if above - and to use the same in the transfer case as in the gearbox.

Personally I have always used cheap 10W-40 in the gearbox and the same 90 weight gear oil as I use in the diffs for the transfer case Apart from gear changes being a bit sticky when cold it seems to work fine

[geeves]

Ive got mobil super (8bucks for 5 liters at local garage) in my gearbox and transfer case. Sychro can be beaten in third but it has 188000 on the clock and anouther 10000 - 20000 due to large tyre speedo error plus or minus any importers adjustment. It can be a little hard to get into gear when realy cold but not bad.
A few people use atf and no bad reports except its better at finding leaks or is that just more noticable being bright red.
Transfer case is the same oil as the gearbox. No harm will occur if you put diff oil in there but ecconomy might suffer a little

[hagar]

ok guys quick question,
does the oil in the gear box have to be diesel grade or does any old engine oil work.
cant see why it wold have to be diesel oil as that would mean a different oil for the petrol versions gearbox.
am just a bit nervous about putting the wrong stuff in.
cheers

[geeves]

No need for diesel oil. I would almost say diesel oil would be bad in gearbox.
Dont worry about putting the wrong stuff in as long as its oil. You wont damage anything.
Mine was good with mobile super ($8 special) for many years but was due to be changed so I put Caltex special ($14) and now get stiff changes when cold. Summers comming so oil wont be cold for long.
Talking to a couple of mechanics they suggest either Castrol VMX or Valvolene Duragear but these have a rating of 75w90 and GL5 Gear oils have the viscosity measured differantly so one day I will sit down and work out if GL5 sae 75w90 is roughly the same viscosity as 20w40 engine oil. It sounds the same when shaken but that is not a scientific test.

[agin]

Last week were changing oils in Auto transmission and transfer box.
I’ve filled Dextron to the transmission, and when I start to fill transfer box with gear oil there was Dextron coming out of it.
I thought that dextron should be in Auto transmission only. I’ve never changed before oil in transfer box, so wondering is it normal that it is filled with dextron?
4jb1t Mu Automatic transmission.

[geeves]

In the xfer case you can get away with anything. Dexron is basicaly a gear oil with additives that make it act like a hydrolic oil and work with wet type clutch packs. These additives are a waste in a std gearbox or xfer case but will not do any harm.
A fairly common fault to watch out for in the Mua gearbox is the failure of the seal between the gearbox and xfer case. In extrem cases this can empty the gearbox into the xfer case which will overflow everywhere but if you dont notice the gearbox ends up running with no oil. Always change your xfer case oil first and also remove the filler plug before the drain plug for this reason. If its starting to leak the xfer case will be overfull.

On a side note several mechanics recomend either Castrol VMX or Valvolene Duragear. Both are supposidly designed for 5 speed gearboxes but have a rating of GL5 and viscosity of 75w85. Gear oils are measured differently to engine oil and a coversion table I have here gives an equivilent rating of 10w30. This would mean that these oils are ok for use in our gearboxes although a lot dearer than the oil I have in there now. Do NOT use any oil with hypoid additives although I wonder how lim slip would go.

[Paaji]

For Transfer Case, recommendations are:
Castrol: SYNTRANS 75W/85
Valvoline: PROBLEND 10W-30 or XLD LO-VIS 10W-30
Penrite: MANUAL GEAR OIL 75

These all meet the specs laid down by Isuzu.

J