Top off 75w90 w/ 75w140 Rear Diff?

[SavagePatch]

The capacity of the rear differential on my CX-9 is just a little over 1qt of 80w90. The capacity of it's transfer case is just a little over .5qt of 75w140. I use RP Max Gear in both.

When I change both of them out can I use the left over 75w140 from the transfer case to top off the rear differentials 75w90? To avoid buying an extra qt of 75w90.

 

[CT8]

Yes.

 

[threeputtpar]

Yes you can use the 75W-140 for the rear diff.

Have you seen the threads about the PTU in Ford/Mazda vehicles? Curious to know how your PTU fluid is doing when you remove it.

 

[SavagePatch]

Originally Posted By: threeputtpar

Have you seen the threads about the PTU in Ford/Mazda vehicles? Curious to know how your PTU fluid is doing when you remove it.


Yes, I replied near the bottom of the second page. I get the fluids warm and then use a big plastic syringe and a short tube to pull as much of the old fluid out through the fill hole as I can. Maybe .5 to .75 of the capacity. It's always black but not as thick as grease. I've done it twice and there was a lot of "fuzz" on the magnetic fill plug both times. This will be my third time and now that I have my method and tools down it'll be and breeze compared to the first time. I plan on doing it every spring before camping/road trip season.

Check out the tool I linked to on Amazon. Works great.

 

[LeakySeals]

Yes. It's viscous in the transfer case so the viscosity matters. For the diff it's just lubrication. The thinner viscosity is for mileage. Less effort pushing through with inner fluid in the diff

 

[aquariuscsm]

I tried a heavier viscosity in my rear diff one time and it was horrible. Made it noisy and felt like I was pulling a trailer. I'd stick with the spec viscosity and not go thicker.

 

[AZjeff]

Hard to imagine that little bit of 75w-140 could be felt.

 

[zeng]

Originally Posted By: aquariuscsm
I tried a heavier viscosity in my rear diff one time and it was horrible. Made it noisy and felt like I was pulling a trailer. I'd stick with the spec viscosity and not go thicker.



It may happen with excessively thicker oil than recommended.

Appreciate if you could let us know the viscosity grades of the two respective oils in question.

 

[aquariuscsm]

Originally Posted By: zeng
Originally Posted By: aquariuscsm
I tried a heavier viscosity in my rear diff one time and it was horrible. Made it noisy and felt like I was pulling a trailer. I'd stick with the spec viscosity and not go thicker.



It may happen with excessively thicker oil than recommended.

Appreciate if you could let us know the viscosity grades of the two respective oils in question.

I filled an 80W90 app with 75W140. Hated it!

 

[zeng]

Originally Posted By: aquariuscsm
Originally Posted By: zeng
Originally Posted By: aquariuscsm
I tried a heavier viscosity in my rear diff one time and it was horrible. Made it noisy and felt like I was pulling a trailer. I'd stick with the spec viscosity and not go thicker.

It may happen with excessively thicker oil than recommended.
Appreciate if you could let us know the viscosity grades of the two respective oils in question.

I filled an 80W90 app with 75W140. Hated it!



Can't argue with your real life encounter though ......I must be missing something here.

Btw, is it equally bad at operating temperature, say 15 minutes into driving ?

Note:At cold start, I can understand your position. IME, one viscosity grade higher should pose no difference while in operation, though admitedly Amsoil 75W140 is marginally thicker than Redline 75W140.

 

[AZjeff]

Was the rear diff on an adult tricycle or a golf cart?

 

[aquariuscsm]

Originally Posted By: AZjeff
Was the rear diff on an adult tricycle or a golf cart?


What the [censored] are you talking about? That's about the most assclownery thing I've ever read on here.

 

[TheOnlySarge]

In my Chevy Silverado (Head/cam-3200 Stall/Shift Kit) I have a Magna-Hytec diff cover for more fluid capacity. Chevy calls for 75-90 from the factory but after we built her up a bit I use 2qts RedLine 75-90 and 2qts RedLine 75-140 for a ~115 @100c. Frankly I can tell no difference in the noise/smoothness from the factory stock setup and fill. I have almost 200K on that abused diff and she is shiny and clean as she can be today.

 

[AZjeff]

Originally Posted By: aquariuscsm
Originally Posted By: AZjeff
Was the rear diff on an adult tricycle or a golf cart?


What the [censored] are you talking about? That's about the most assclownery thing I've ever read on here.


Cool, glad to be the best at something. Those were the only 2 vehicles I could imagine have such low power input that a person might be able to feel the heavier diff lube. You didn't mention what car or truck you put the heavier lube in that bogged it down. Care to share? Did you notice if it slowed faster when you lifted off the accelerator? Serious question.

 

[aquariuscsm]

Originally Posted By: AZjeff
Originally Posted By: aquariuscsm
Originally Posted By: AZjeff
Was the rear diff on an adult tricycle or a golf cart?


What the [censored] are you talking about? That's about the most assclownery thing I've ever read on here.


Cool, glad to be the best at something. Those were the only 2 vehicles I could imagine have such low power input that a person might be able to feel the heavier diff lube. You didn't mention what car or truck you put the heavier lube in that bogged it down. Care to share? Did you notice if it slowed faster when you lifted off the accelerator? Serious question.


Rear diff in my Z. Felt sluggish with Mobil 1 75W140 (car specs 80W90 for all temps via 1990-1996 Z32 fsm). Replaced with Amsoil 80W90 and all was back to normal again.

 

[zeng]

Thanks for sharing.

M1 75W140 has a KV@40*C of 170 cSt and KV@100*C of 24.4 cSt;
It falls in between AGMA 5EP /ISO 220 and AGMA 4EP/ISO 150.

Synthetic Amsoil 80W90 has a KV@40*C of 120 cSt and KV@100*C of 15.5 cSt;
It falls in between AGMA 4EP/ ISO 150 and AGMA 3EP /ISO 100.

A typical mineral 80W90 in Mobilube HD Plus has a KV@40*C of 139 cSt and KV@100*C of 14.5 cSt.
This is an AGMA 4EP /ISO 150 grade.

In 1996, the then SAE 80W90 has a KV@100*C range of 13.5-24.0 cSt.
This covers current day AGMA 5EP /ISO 220 and AGMA 4EP /ISO 150.

TBH, I'm still wondering .... not that I am questioning.