Rear Differential Oil

[Touz]

I'm trying to find the cause of a subtle whining sound in 4th/5th on my HJ75 1989. I checked the rear diff oil level today. Only opened the filler plug and the oil that came out was quite grimy. Is this to be expected?

I was also surprised how much oil came out from just the filler plug, like it had been overfilled. I don't know when it was last changed.

 

[sodafeld1]

Ideally all oil should be fresh as a daisy. If dirty it should be at least changed.

Possible the seal between gearbox and transfer has failed, so your gear box oil ends up over filling the transfer. This is not good for your gearbox. You may need to get a bypass hose which goes from transfer to gear box. terrain tamer and a few dealers sell them readily. Some say it is a temporary fix, but I have run one for at least 100k kms.

Check fluid level in gearbox before going anywhere.

 

[sodafeld1]

and sometimes the perished seal can drain the transfer and overfill the gearbox.

 

[PhillipJFrye]

I'm trying to find the cause of a subtle whining sound in 4th/5th on my HJ75 1989. I checked the rear diff oil level today. Only opened the filler plug and the oil that came out was quite grimy. Is this to be expected?

I was also surprised how much oil came out from just the filler plug, like it had been overfilled. I don't know when it was last changed.

stating the obvious for enthusiasts... eliminate any mystery. change all fluids over time (or all at once) so you know exactly what's in your vehicle's bloodstream. write it all down for future reference. as an amateur wrencher, it has been fun learning how to do all this maintenance. fluids, lubrication, filters, it all gets you more connected to your car. plus it eliminates possible causes of trouble.

 

[JuanJ]

Hello,

Grimy differential oil suggests heavy use, neglect, or both.

Differential oil should look clean. Otherwise, change it.

If you do river crossings, when returning home, check differential oil condition and replace it if necessary.





Juan

 

[sodafeld1]

stating the obvious for enthusiasts... eliminate any mystery. change all fluids over time (or all at once) so you know exactly what's in your vehicle's bloodstream. write it all down for future reference. as an amateur wrencher, it has been fun learning how to do all this maintenance. fluids, lubrication, filters, it all gets you more connected to your car. plus it eliminates possible causes of trouble.

exactly, i call it giving her a birthday party!

 

[Touz]

Ideally all oil should be fresh as a daisy. If dirty it should be at least changed.

Possible the seal between gearbox and transfer has failed, so your gear box oil ends up over filling the transfer. This is not good for your gearbox. You may need to get a bypass hose which goes from transfer to gear box. terrain tamer and a few dealers sell them readily. Some say it is a temporary fix, but I have run one for at least 100k kms.

Check fluid level in gearbox before going anywhere.

Interesting, I just had the gearbox and transfer reconditioned. But what does the seal failing between the gearbox and transfer have to do with the rear diff?

 

[Touz]

stating the obvious for enthusiasts... eliminate any mystery. change all fluids over time (or all at once) so you know exactly what's in your vehicle's bloodstream. write it all down for future reference. as an amateur wrencher, it has been fun learning how to do all this maintenance. fluids, lubrication, filters, it all gets you more connected to your car. plus it eliminates possible causes of trouble.

Funny you say that. Last night I made spreadsheet for a maintenance schedule, I'll record all the details there!

Also, I've bought an old Gregory's repair and service manual for it and have had a lot of fun reading through it. Already helped with a few minor repairs.

 

[Touz]

Hello,

Grimy differential oil suggests heavy use, neglect, or both.

Differential oil should look clean. Otherwise, change it.

If you do river crossings, when returning home, check differential oil condition and replace it if necessary.





Juan

Thanks, next job on the list is to change it.

 

[WarDamnEagle]

But what does the seal failing between the gearbox and transfer have to do with the rear diff?

Nothing. They have the two confused. Just change the oil in the rear differential. Check it in a few months or as @JuanJ said, after a river crossing. But also check your rear diff breather cap and make sure it still allows air to pass when you change your fluid.

 

[Eurasiaoverland]

Interesting, I just had the gearbox and transfer reconditioned. But what does the seal failing between the gearbox and transfer have to do with the rear diff?

I think sodafeld skimmed your first post and understood you are talking about an overfilled transfer, which is a common problem on earlier H55Fs.

Dirty water/oil emulsion is a thick greeny-grey mess. Drain a bit from the lower plug and see if there is any water there. And as above, check your breather plug. If water has been in there, I would pull the diff (third member) and check that for problems. If there are any signs of leaking at the pinion shaft seal (behind the flange) then get the diff looked at.

 

[sodafeld1]

whoops sorry, did skim, duh. If I did pay for any service from any mechanic I would expect it to be in pretty good nick when I got it back. No whines in 4th, 5th.
Must admit a big appeal of lc's are they are easy to work on compared to most cars, so don't need a mechanic for them. I know a few pro indy mechanics and juggling a business and doing a thorough job is not easy. No one would or could do a good a job as yourself unless you have very deep pockets.

Example if I rebuilt the gearbox , I would check the diff and driveshaft whilst at it. Few mechanics have the time to do so, and it was not on the list of requests. A sloppy driveshaft would be too obvious to ignore surely.

But if your own love, you would.

Gear box, transfer, drive shaft and diffs are interrelated and each can affect each other. If your driveshaft is sloppy it can damage your transfer or diff for another example.

diff oil should be clean. fellas above are right.

Get the toyota service manual , they are excellent. Makes gregory's look like a cryptic crossword. Work through the whole drivetrain, gearbox is a bigger one, if done right.

 

[Felde]

Hi
Obviousl a bit of confusion here on what was checked. I recommend to reset to square one.
@Touz :
First identify the source of the whine: Gearbox or diff. Have a passenger crawl around in the car when driving and help identify where it comes from.
Also carefully observe changes when accelerating or being in push.
Go from there.

Obvious: Check oil in gearbox and tranny, if not yet done.
How many km since last (assumed) change?
Do you have plugs with magnets? (If not: Time to get those).
On good gearbox and tranny, the oil should be clear after 20000+km (I changed mine last Friday and found it that way).
Check for debris. If necessary: Filter the oil to check for debris. Whine equals tear, which at minimum produces some glitter.
Notes on different filling levels between gearbox and tranny due to the seal issue have been made already.

On a rear diff you might experience:
Brown color, but oil is clear: In particular noticed on LSD diffs: The LSD friction pads burn the oil a bit. That's normal. Note LSD diff needs special oil / additive.

Graphite black, cloudy or even intransparent oil: MoS2 greas from the wheel bearings made it into the oil. (applies to front and rear diff). The oilseals on the axle are not happy, but not necessarily shot. This also may happen as a result of clogged axle breathers: Not only may oil seap trough the seal into the bearing when expanding, but also grease or grease-oil-mixture can be sucked in when the axle cools. I had that on my front axle. After declogging the breather the seals had another 10000km life.
Also note: The drain plug is not straight at the bottom of the diff. Some residue oil remains in the diff T its bottom, and also other residues may accumulate there. Also grease sticks to the sidewalls. If the axle ever had an issue with grease in oil, you will see some clouds in the oil for a long time, unless you remove the diff cover and flush the housing (which is rarely done and also mostly unnecessary).

'Cappucino' foamy condition, which indicates water in the oil. Either trough the breather our trough really shot seals. (applies to front and rear diff)

Concerning overfill of any oil reservoir:
This usually happens when oil is filled while the rig is on the hoist:
Modern 4 arm hoists reach to the frame, mostly also using some sort of extension.
The frame isn't straight, causing the vehicle to lean to the front. Not being level causes overfill.
Check with who did the last change on what might have happened in this regard.

Good Luck Ralf

 

[Touz]

Hi
Obviousl a bit of confusion here on what was checked. I recommend to reset to square one.
@Touz :
First identify the source of the whine: Gearbox or diff. Have a passenger crawl around in the car when driving and help identify where it comes from.
Also carefully observe changes when accelerating or being in push.
Go from there.

Obvious: Check oil in gearbox and tranny, if not yet done.
How many km since last (assumed) change?
Do you have plugs with magnets? (If not: Time to get those).
On good gearbox and tranny, the oil should be clear after 20000+km (I changed mine last Friday and found it that way).
Check for debris. If necessary: Filter the oil to check for debris. Whine equals tear, which at minimum produces some glitter.
Notes on different filling levels between gearbox and tranny due to the seal issue have been made already.

On a rear diff you might experience:
Brown color, but oil is clear: In particular noticed on LSD diffs: The LSD friction pads burn the oil a bit. That's normal. Note LSD diff needs special oil / additive.

Graphite black, cloudy or even intransparent oil: MoS2 greas from the wheel bearings made it into the oil. (applies to front and rear diff). The oilseals on the axle are not happy, but not necessarily shot. This also may happen as a result of clogged axle breathers: Not only may oil seap trough the seal into the bearing when expanding, but also grease or grease-oil-mixture can be sucked in when the axle cools. I had that on my front axle. After declogging the breather the seals had another 10000km life.
Also note: The drain plug is not straight at the bottom of the diff. Some residue oil remains in the diff T its bottom, and also other residues may accumulate there. Also grease sticks to the sidewalls. If the axle ever had an issue with grease in oil, you will see some clouds in the oil for a long time, unless you remove the diff cover and flush the housing (which is rarely done and also mostly unnecessary).

'Cappucino' foamy condition, which indicates water in the oil. Either trough the breather our trough really shot seals. (applies to front and rear diff)

Concerning overfill of any oil reservoir:
This usually happens when oil is filled while the rig is on the hoist:
Modern 4 arm hoists reach to the frame, mostly also using some sort of extension.
The frame isn't straight, causing the vehicle to lean to the front. Not being level causes overfill.
Check with who did the last change on what might have happened in this regard.

Good Luck Ralf

Thanks for the reply Ralf. I have just had the gearbox and transfer rebuilt a couple of weeks ago. So I believe that the sound I'm hearing is coming from the rear diff (as this was suggested to me by the mechanic who helped with rebuild of gearbox and transfer). I am going to drain and fill the rear diff and see if that makes a difference to the sound... hoping I don't need to shovel out more cash on this thing for a diff rebuild too

 

[Felde]

Right path. If it helps: Fine.
But if the diff was under suspicion already, you should probably pull the cover and inspect it to plan your next move.
There might be a long way between whine and failure. If it's 'just' excessive wear, but teeth are generally ok / no break outs, a proper adjustment might buy you some more time. That's just work and quite cheap if you can do it yourselves or find a mate to help.
If the gears are really damaged, you'll know then.
It depends a lot on what you use the truck for and what the consequences of a breakdown would be.
Good Luck Ralf

 

[jayp2]

rear diff oil looking nasty can also be a result of inner axle oil seal and cross pollination of hub grease and diff oil (think birf soup)

 

[Touz]

whoops sorry, did skim, duh. If I did pay for any service from any mechanic I would expect it to be in pretty good nick when I got it back. No whines in 4th, 5th.
Must admit a big appeal of lc's are they are easy to work on compared to most cars, so don't need a mechanic for them. I know a few pro indy mechanics and juggling a business and doing a thorough job is not easy. No one would or could do a good a job as yourself unless you have very deep pockets.

Example if I rebuilt the gearbox , I would check the diff and driveshaft whilst at it. Few mechanics have the time to do so, and it was not on the list of requests. A sloppy driveshaft would be too obvious to ignore surely.

But if your own love, you would.

Gear box, transfer, drive shaft and diffs are interrelated and each can affect each other. If your driveshaft is sloppy it can damage your transfer or diff for another example.

diff oil should be clean. fellas above are right.

Get the toyota service manual , they are excellent. Makes gregory's look like a cryptic crossword. Work through the whole drivetrain, gearbox is a bigger one, if done right.

When you say "toyota service manual", is that different from the owners manual? I assume this is something that has to be hunted down second hand?

 

[AirheadNut]

When you say "toyota service manual", is that different from the owners manual? I assume this is something that has to be hunted down second hand?

Also known as the FSM, or Factory Service Manual, they are full, detailed service manuals for every aspect of the vehicle. You'll need two: the engine manual and the chassis/body manual for your applicable model. They should be available for download under the Resources tab here or at CruiserCult.

 

[Touz]

Also known as the FSM, or Factory Service Manual, they are full, detailed service manuals for every aspect of the vehicle. You'll need two: the engine manual and the chassis/body manual for your applicable model. They should be available for download under the Resources tab here or at CruiserCult.

thanks

 

[sodafeld1]

zactly! I love the toyota manuals for the 40s and hj75s that I have. So easy to follow, clearly explained, perfect images, crisp, concise. The hard copies are lovely as you don't need to keep looking at the illuminated screen. Closest thing to a bible I have as I refer to them often, and then mud, then youtube in that order.
I reckon they lost a bit of clarity starting at hzj75's era in the factory service manuals. My mate has one for his hzj on his ipad but it keeps going to battery save mode, so have to open ipad and punch in password every 5 mins. Books are good.
Sometimes you see the fsm's on ebay or fb marketplace.
Where in Melbourne are you situated?