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Discussion Starter #1 (Edited)
re: Read Diff Gear Oil

Aloha Folks-

Hope you can send me some suggestions for gear oil for my rear differential. I have a small leak, so I will be putting on the newer 2008 F250 finned diff cover and know that I need to get slightly longer bolts and get some washers as well. I will be using Permatex Grey for the sealant.

My question is what brand(s) would you recommend for the gear oil? I was advised if I could find 90w-140 synthetic but it is hard to locate. I was also told that 75w-140 is just find and a few brands make 85w-140 as well a synthetic gear oil. So, any and all recommendations are welcomed and if you can locate these at O'Reilly's, Autozone, Walmart, etc?

I have already purchased the Ford Motorcraft additive as I have 4.10 LS to be added to whatever I put in.

Thank you in advance for you help.

Mahalo!

ps: not sure if this is important or not, my truck is a 1996 F250 4x4 which has the RSK d60 in the front.
 

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the easiest to find in synthetic is the Valvoline maxlife ..... however o rielly brand (master pro) is what I run in my work trucks ..... and in my personal trucks I use shell synthetic for every fluid except the mercon lv
 

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Discussion Starter #3
Aloha LittleF450-
Thank you for your input. Did you get your Shell Synthetic at O'Reilly's? I spoke to a person at O'Reilly's and they said they had a "synthetic-blend" that was 85w-140 (I am pretty sure that is what he said), it was around 8.00/qt. Quite a bit cheaper than Royal Purple, Lucas was a little higher than the O'Reilly's brand.

Thanks again.
Mahalo


the easiest to find in synthetic is the Valvoline maxlife ..... however o rielly brand (master pro) is what I run in my work trucks ..... and in my personal trucks I use shell synthetic for every fluid except the mercon lv
 

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The factory recommendation for the '97 is 75w-90 synthetic.

Use whatever brand you can find or that you're partial to. They all meet the same industry standards and requirements for their respective ratings.

I use Redline in mine.
 

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I use regular Dino 80W90..... but I change it frequently since I have a Disco/Fabulous Aluminium cover with a drain....
 

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Discussion Starter #6
re: Redline

Aloha Snowtow-
I was just going to ask a question about Redline. I spoke to an auto supply store that carries Redline and they say they have the 75w-140 synthetic and it includes the friction modifier in it.

When you put it into your rear diff, did you still add in the Motorcraft additive? If so, did you put in the recommended 8oz?

Mahalo!


The factory recommendation for the '97 is 75w-90 synthetic.

Use whatever brand you can find or that you're partial to. They all meet the same industry standards and requirements for their respective ratings.

I use Redline in mine.
 

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I have yet to find one that says it already has additive in it,that I didn't have to add it.They come back when bed is loaded and they are starting up a slope and turning at same time.
 

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Long as yer in there, it's good time to wipe the slime off the sensor ring or whatever it's called, wipe all that slime out, my speedo quit bouncing after changing the gear oil and cleaning it out, (i also fixed the ground straps on the frame at the same time) so I'm not sure what fixed the speedo for sure..:jester:

the gear oil sure was dirty, and metal shavings on the fill plug too
 

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Discussion Starter #10
Aloha blageurt, MdieselN, Snowtow and Stan-

Thanks for all this info! I had spoke to one person that uses the synthetic oil and as Snowtow mentioned, did not need the Ford additive, then I have met others who said with synthetic, they had too. I also thought blageurt about going with the dino oil too, saw a synthetic blend 85W-140 that was a good price. The Valvoline Synthetic is about 12.99/qt and the Royal Purple Synthetic 15.99/qt, both 75w-140 at Autozone. The store with the Redline Synthetic 75w-140 was 14.99/qt. So these all seem to be close in price.

I will still get some of the Motorcraft additive to have on hand. From what I have read, it does not hurt if you add some in, even if the oil you put in says it has the friction modifier in it. Hope that is correct.

Thanks again for all your help!
Mahalo
 

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The only thing you need to worry about foaming / cavitation when it gets hot it can foam...That is why Synthetics are the way to go .....Friction Modifyer you can buy...you do not want it to grenade......I can tow real heavy sometimes in the places we don't speak of.....I change mine frequently ....like I said at the begining.....
 

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Discussion Starter #12
Aloha blageurt-

Thank you very much for explaining the difference between the dino vs synthetic. I wish I had a setup whereby I could change out more often like you but I do not, so maybe I will go with Synthetic and make sure to get the Motorcraft modifier.

I also was advised to get the updated diff cover that was used on the 2008 F250/350. I need to run down some new bolts and I believe the ones our axles take is a 5/16 (18 pitch) thread but they said to get longer like 1.25in long. I am sure if I am off someone will chime in. The other part for this is if I go with the regular "socket-head" type of bolt that is on there now or a hex head type. With your cover what type of bolts did yours come with and does it matter, as I know there are specific torque requirements.

Thanks again.
Mahalo!

The only thing you need to worry about foaming / cavitation when it gets hot it can foam...That is why Synthetics are the way to go .....Friction Modifyer you can buy...you do not want it to grenade......I can tow real heavy sometimes in the places we don't speak of.....I change mine frequently ....like I said at the begining.....
 

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The updated diff cover swap has been covered on the web with the details you need. There are several PSD forums with more activity than this one to browse for info like that. ;)

Google is your friend.
 

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Bolts do not matter unless you get an aluminium cover .....which is thicker.....so naturally the bolts have to be longer......Torque is the same ( 30-40 lbs-ft. ) on my last change I lost one of the Allen bolts so I have 1 hex head out of the 12 .....
 

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The factory recommendation for the '97 is 75w-90 synthetic.

Use whatever brand you can find or that you're partial to. They all meet the same industry standards and requirements for their respective ratings.

I use Redline in mine.
There was a TSB 10-12 yrs ago, maybe longer, that changed the recommended diff lube to SAE 75-140 or 85-140. The rear diff runs hot enough under heavy load in warm temps to need the SAE 140 at temp. Same TSB applied to the 10-1/2" axle in the S-D's.

I've run Amsoil in my truck for 200,000 miles with no problems other than a leaky pinion seal. I have 3.55 gears and Traction-Loc, so add the additive even though Amsoil says it's not needed. The T/L still works great too.

Whatever viscosity you run, should be synthetic since it was factory filled with synthetic.
 

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Oh crap, I meant to type 75-140 and didn't even notice that. Good catch Dr. Evil!

The TSB must have been for earlier models as the factory spec. on my '97 was 75-140. That's all I've ever used in mine since new, assuming that's what the factory installed.
 

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Discussion Starter #17
Aloha Dr-

Thank you for this. We put in Vavoline Synthetic 75w-140 plus the Motorcraft additive (2 bottles). Seems to be fine and with the new Super Duty cover looks good. I did fine some Grade 8 black colored bolts of all places at O'Reilly's and somewhere else picked up some grade 8 washers and it all went together well. Thank you all for your input and advice. I hope we do not have to service this for quite some time!

Mahalo!

There was a TSB 10-12 yrs ago, maybe longer, that changed the recommended diff lube to SAE 75-140 or 85-140. The rear diff runs hot enough under heavy load in warm temps to need the SAE 140 at temp. Same TSB applied to the 10-1/2" axle in the S-D's.

I've run Amsoil in my truck for 200,000 miles with no problems other than a leaky pinion seal. I have 3.55 gears and Traction-Loc, so add the additive even though Amsoil says it's not needed. The T/L still works great too.

Whatever viscosity you run, should be synthetic since it was factory filled with synthetic.
 

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SNOWTOW - It may have been that long ago, my op's manual & Helm's '96 factory manuals all say 75W-90, and I remember the factory fill synthetic fluid seemed REALLY thin, about like ATF, and was kinda green. I even put 75W-140 in my Wife's '03 Mercury Mountaineer, mostly to stop a leaky seal.

Don't you just hate it when your 'Puter types stuff wrong? ;-) Happens to me all the time too.
 
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Aloha Folks-

Hope you can send me some suggestions for gear oil for my rear differential. I have a small leak, so I will be putting on the newer 2008 F250 finned diff cover and know that I need to get slightly longer bolts and get some washers as well. I will be using Permatex Grey for the sealant.

My question is what brand(s) would you recommend for the gear oil? I was advised if I could find 90w-140 synthetic but it is hard to locate. I was also told that 75w-140 is just find and a few brands make 85w-140 as well a synthetic gear oil. So, any and all recommendations are welcomed and if you can locate these at O'Reilly's, Autozone, Walmart, etc?

I have already purchased the Ford Motorcraft additive as I have 4.10 LS to be added to whatever I put in.

Thank you in advance for you help.

Mahalo!

ps: not sure if this is important or not, my truck is a 1996 F250 4x4 which has the RSK d60 in the front.
Redline oil is really hard to beat!
 
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