Dex VI in Dex III spec'd differential ?

[gomes512]

Our Geo has separate diff and trans fluids (both spec Dex III). I filled the trans with bulk supertech ATF and the diff with leftover DexVI I had from another application. I heard that some older Toyota auto's don't like Dex VI, not sure if there is any truth to that?

What about the differential? The Hayne's manual I have is a British version and only goes over routine maintenance. Not sure what the diff looks like inside (first fwd car). Should I keep it?

Thanks for any input.

 

[Bluestream]

ATF in a differential? Now that's scarry.

Most FWD cars only gave a transmission and not a diffy like a RWD which would require hypoid lube

 

[Boomer]

Yes, if it is a ring and pinion, ATF will burn it out in a short period of time!

 

[Kestas]

Facts:

GM has back-spec'ed Dex VI to work in most of their Dex III transmission applications.

Dex VI has a slightly lower viscosity than Dex III.

Dex VI has twice the life of Dex III because it is more shear stable and resistant to oxidation.


For discussion:

Is the GEO considered a GM vehicle? It sounds japanese, and the Dex VI may not be approved for that transmission.

Though Dex VI is slightly lower in viscosity, Some say that Dex III shears down during use to the same level as Dex VI, which is more shear stable, so the difference in viscosity is not a big issue. I imagine anything that specifies Dex III should run okay on Dex VI. Why would GM mess with other fluid characteristics such as friction modifiers and detergency in the specification?

What's wrong with ATF in the differential? Most FWD transaxles are lubed with ATF. OTOH, that's only because the differential shares the same sump with the transmission. With separate sumps, I would expect different fluids that are optimal to each unit.

 

[gmctodd]

FWIW,

Dex VI is not backwards compatible with Dex III in every situation.

Example: My 05 2500HD spcs Dex III in the transfer case, but GM says Dex VI can not be used in its place. So it may be true in your situation as well.

 

[440Magnum]

Originally Posted By: Bluestream
ATF in a differential? Now that's scarry.

Most FWD cars only gave a transmission and not a diffy like a RWD which would require hypoid lube


There's some misinformation out there. The term "hypoid" refers to a specific type of cut on ring-and-pinion gears. Specifically, its the helical cut that allows the gears to mesh correctly when the centerline of the pinion is lower than the centerline of the ring gear. As hypoid gears mesh, there is a high-pressure "brushing" contact between them, hence the need for extreme pressure ("hypoid") gear lubricants like API GL-4 and GL-5.

OK, got that. Now all FWD cars DO have a differential that allows the left and right wheels to turn at different rates. The key difference is that *lots* of FWD cars have differentials that do NOT have hypoid-cut gears anywhere in them. That's because one of the big driving factors for using hypoid gears at all is to be able to lower that cetnerline of the driveshaft so that its lower than the centerline of the rear axle, allowing a lower floorpan line. This is not usually an issue in most front-drives since the pinion is driven by an intermediate shaft that is also inside the transaxle housing. So if there are no hypoid-cut gears, there's no need for a hypoid lube.

That said, SOME FWD cars do have hypoid diffys (like the Chrysler LH series with the 42LE transaxle, since the engine is mounted longitudinally and packaging worked better with a transfer chain and then a pinion mounted offset from the half-shaft centerline) and they do need GL-5 lube in the diff. section.

As to whether Dexron VI is an acceptable replacement for Dexron III in this applicaition... I dunno. I have seen that Dex VI is rather lower viscosity than Dex III, so that might be an issue. But I doubt it- basically all automagic transmissions have gears (not hypoids, but at least helical-cut gears) and so pretty much any transmission lube has to protect those. The bigger differences are in the friction modifiers that affect how the multi-plate clutches and the torque convertor lockup clutch behave.

 

[Eddie]

ATF works very well in specific applications including differentials IF the gear design permits it. ATF is an outstanding lubricant when used as intended.

 

[dailydriver]

Originally Posted By: gmctodd
FWIW,

Dex VI is not backwards compatible with Dex III in every situation.


Yessir!
It is also VERBOTEN in Dex 3 specced T56 manual gearboxes!!

 

[gomes512]

440, that's some great info.

Yes, it specs transmission fluid. Not a typo.

Kestas, I'm not sure if the Geo is considered a true GM vehicle or not. It does certainly have a GM vin# but from what I've read it is a direct corolla clone.

Last time I went to the dealer to get a key cut, the service guy gave me that "I didn't know they were still any on the road."
look.

gmctodd, I had the same concern with the trans. Decided to stick with the supertech atf (says its made for trans's specing dexIII)


So if this was your vehicle would you keep the DexVI in the diff in for the winter? I'd hate to waste good fluid.

 

[JustinC25]

It's probably not related, but I did a drain and fill on my friends '97 Camry, with ST. Dex VI (They didn't have any D-III @ WM at the time in any brand.)
Within 3k the trans let go. Again probably not related, but I don't want to use it in a Toyota trans that spec'd D-III.
The car only had 150k on it when the trans let go. The previous from what I can tell was not good about maintenance. As evidenced by these pics: http://s45.photobucket.com/albums/f61/justincartier/Camry/

I had to replace the engine when we bought it. The woman was recently divorced, and I think her exhusband had handled all the maintenance.

 

[gomes512]

Thanks for sharing Justin, great pics by the way. Yeah, I'm definitely not putting anything but dexIII in the trans.

Again I'm not sure if the diff is something simple that can handle anything as long as it ain't olive oil or if it is sensitive to fluid type. My guess is probably not as when I drained the fluid in the diff, when I get the car, it came out pitch back and flowed faster than water.

Any thoughts on this?

 

[JustinC25]

I run T-IV in my Camry, it has the same setup, with a different drain and fill for the diff. It has 252k on it, and until last year it has had D-III in the diff, and has been fine. It's what Toyota specs for it. I also maintain 5 other Camry's with this same setup, and I use Pennzoil Dexron ATF exclusively, and they are all fine.

 

[JustinC25]

Also forgot to mention, just keep the diff fluid changed every 30k and you will be fine.

I just did another Camry yesterday, and the diff fluid was fairly dark. I believe it was the factory fill though. It had 64k on it, and was probably in there since '01.

 

[endeavor to persevere]

This from an older GM bulletin..

Precaution: DEXRON-VI in Manual Transmissions

When DEXRON-III is indicated as the fluid fill for manual transmissions and transfer cases, DO NOT use DEXRON-VI. Instead, use GM Manual Transmission Fluid p/n 88861800 in these components.

TIP: Refer to PIP3836B (Feb. 2007).

If the manual transmission or transfer case indicates use of DEXRON-VI, then, of course, it should be used.

Purging Equipment

 

[gmctodd]

Originally Posted By: endeavor to persevere

This from an older GM bulletin..

Precaution: DEXRON-VI in Manual Transmissions

When DEXRON-III is indicated as the fluid fill for manual transmissions and transfer cases, DO NOT use DEXRON-VI. Instead, use GM Manual Transmission Fluid p/n 88861800 in these components.

TIP: Refer to PIP3836B (Feb. 2007).

If the manual transmission or transfer case indicates use of DEXRON-VI, then, of course, it should be used.

Purging Equipment



Good find

That's what I was referring to!

 

[Ken2]

Some GEOs were Suzukis, some were Toyotas. Use only a Dexron-III fluid.

Dexron-VI is certified only for GM Hydramatic transmissions and certain others that have been tested for Dex-VI. It is not suitable for just about every non-GM transmission---including the GEO.