85w140 in Ford 8.8

[1978elcamino]

Vehicle is a 2018 f150 5.0 4x4 80k miles original owner.

Pinion seal was leaking so when I replaced the seal I also replaced the OEM factory fill with Valvoline 85w140.
If you know anything about the early 10r80 then you know the torque converter is pretty much always locked, even on decel. With that, ever since new when you get back on the throttle there was always a clunk sound at the differential. So, I figured I would try a thicker oil and I am very happy to say the clunk is gone.

In Florida I doubt the need for a thin oil exists and my benefit of no clunk very much outweighs any loss in any MPG caused by the high viscosity.
Just though I would share in case anyone with a newer f150 has a diff clunk after getting back on the throttle that annoys the sh.t out of them.

 

[Lubener]

That is the weight I used for my Ford 8.8. If you have a LSD, you may have to add some LSD additive.

 

[thastinger]

Kinda sad what they have done over the years WRT drivetrain capacity reduction. My 98 F150 4x4 has an 8.8 but it is in the front, the rear is a 9.75.

 

[1978elcamino]

That is the weight I used for my Ford 8.8. If you have a LSD, you may have to add some LSD additive.

It is the electronic locker and does not require LSD additive or friction modifiers.
Personally, I would much rather have the LSD as I find the auto locker pointless and annoying.

 

[1978elcamino]

I might also add that I plan an using the 85w140 in the front diff when I get time to tackle it.

 

[1978elcamino]

Kinda sad what they have done over the years WRT drivetrain capacity reduction. My 98 F150 4x4 has an 8.8 but it is in the front, the rear is a 9.75.

If you have the Spicer 9.75" diff you have the heavy payload package or the 7700 model F150.
All 97-2004 Heritage F150's came with the 8.8 except the Lightning, 7700 or the heavy payload pkg or some other unusual package that required the Spicer 9 3/4 diff. Standard issue has been the 8.8 for decades. But, thats good for you though, the 9.75 is a very good, strong diff.

 

[thastinger]

If you have the Spicer 9.75" diff you have the heavy payload package or the 7700 model F150.
All 97-2004 Heritage F150's came with the 8.8 except the Lightning, 7700 or the heavy payload pkg or some other unusual package that required the Spicer 9 3/4 diff. Standard issue has been the 8.8 for decades. But, thats good for you though, the 9.75 is a very good, strong diff.

It is actually a Sterling and I have the "max tow" package. 5.4/4R100 tranny/9.75 rear and 8.8 front. It is not a LD 250, I don't have 7 lug wheels.

 

[D60]

Kinda sad what they have done over the years WRT drivetrain capacity reduction. My 98 F150 4x4 has an 8.8 but it is in the front, the rear is a 9.75.

The 4.6 got the 8.8 in the bubble bodies. You can typically identify engine size by the rear end -- something I notice on the road everyday 'cause I'm a gearhead.

My '07 F150 XL 4x4 with 4.6 2V has the 8.8 with 240k miles on it. I've owned it since 185k and never touched the rear diff.

That said, if my 8.8 craters I might shop for a 9.75 to swap just because.

I think recent 8.8s are a "super" 8.8 and more heavy duty.

 

[D60]

If you have the Spicer 9.75" diff you have the heavy payload package or the 7700 model F150.
All 97-2004 Heritage F150's came with the 8.8 except the Lightning, 7700 or the heavy payload pkg or some other unusual package that required the Spicer 9 3/4 diff. Standard issue has been the 8.8 for decades. But, thats good for you though, the 9.75 is a very good, strong diff.

Yeah the 8.8 and 9.75 are Ford corporate axles. Not Spicer.

I remember being confused on the first bubble bodies in '97: "it looks like a 10.25 but is 5 lug semi-float. WTH?"

 

[tcp71]

If you have the Spicer 9.75" diff you have the heavy payload package or the 7700 model F150.
All 97-2004 Heritage F150's came with the 8.8 except the Lightning, 7700 or the heavy payload pkg or some other unusual package that required the Spicer 9 3/4 diff. Standard issue has been the 8.8 for decades. But, thats good for you though, the 9.75 is a very good, strong diff.

Nah. Ford's 9.75 has been a standard for a long time. The 12 bolt heavy duty 8.8 started use in 2015 on the 2.7tt trucks. You are mistaking the 9.75 (6 bolt) with the ford 10.25 (7bolt) that came on the 7700 models.

https://differentials.com/ford-10-25-10-5-differential-parts/

 

[thastinger]

The 4.6 got the 8.8 in the bubble bodies. You can typically identify engine size by the rear end -- something I notice on the road everyday 'cause I'm a gearhead.

I guess my point was that the 5.4 2V of the day did not make the power of the modern Coyote motors and the truck did not have the advertised towing capacity of the modern F150s...yet the rear axle was a 9.75 and the front was an 8.8....why would I need a 9.75 rear end to be able to tow 3K LESS than a 2018 F150 is supposed to be able to?

And if you say it is the frame that is the difference in towing capacity then why would Ford put a 9.75 rear end in a vehicle that can only use half of the 9.75's capabilities?

 

[4WD]

Nah. Ford's 9.75 has been a standard for a long time. The 12 bolt heavy duty 8.8 started use in 2015 on the 2.7tt trucks. You are mistaking the 9.75 (6 bolt) with the ford 10.25 (7bolt) that came on the 7700 models.

View attachment 272671

View attachment 272672

https://differentials.com/ford-10-25-10-5-differential-parts/

Never noticed a 7 lug, wow.

 

[D60]

I guess my point was that the 5.4 2V of the day did not make the power of the modern Coyote motors and the truck did not have the advertised towing capacity of the modern F150s...yet the rear axle was a 9.75 and the front was an 8.8....why would I need a 9.75 rear end to be able to tow 3K LESS than a 2018 F150 is supposed to be able to?

And if you say it is the frame that is the difference in towing capacity then why would Ford put a 9.75 rear end in a vehicle that can only use half of the 9.75's capabilities?

My FIL has a '97 with the 5.4. The non-PIs were total dogs. Ford just wanted to believe their new Triton was UHMAYZZING and needed a larger rear axle.

I remember my FIL being annoyed by his gas mileage when his Chevy friends with pushrods were pulling down at least several MPG better than him. "What's the point of overhead cams, then?" he'd ask. I still have no good answer

 

[1978elcamino]

It is actually a Sterling and I have the "max tow" package. 5.4/4R100 tranny/9.75 rear and 8.8 front. It is not a LD 250, I don't have 7 lug wheels.

CRAP, yes I meant sterling. Those were standard with the HD max tow, 7700 or the LD250 heritage.

 

[1978elcamino]

Never noticed a 7 lug, wow.

Yeah, it was interesting. Ford made a F150 7700 pkg. Think of it like a light duty f250 with f150 badges with a gvwr between the f150 and f250. I believe the f150 was 6500gvwr, f250 was8800 and the f150 7700 was, well it was 7700gvwr. Heavier brakes, heavier springs and shocks, and parts of the frame where stronger. It came with the 5.4 and 4r100 and the 9.75 rear end that actually began the this banter. Oh, dont forget the 7 lug wheels. The next gen also had a payload pkg with the 7 lug wheels too.
And the most important part was the f150 badge that said 7700 just below it.

 

[1978elcamino]

I guess my point was that the 5.4 2V of the day did not make the power of the modern Coyote motors and the truck did not have the advertised towing capacity of the modern F150s...yet the rear axle was a 9.75 and the front was an 8.8....why would I need a 9.75 rear end to be able to tow 3K LESS than a 2018 F150 is supposed to be able to?

And if you say it is the frame that is the difference in towing capacity then why would Ford put a 9.75 rear end in a vehicle that can only use half of the 9.75's capabilities?

Torque is the reason.
From an owner of a new Coyote f150 that tows quite a bit I can say the 5.4 has better low rpm torque for towing.
I have used my fathers previous 5.4 to tow and IMO it did better. Is it possible that Ford thought the older 28 spline 8.8 was not up to task and decided the 9.75 would be a better fit? Maybe, idk.
I believe the super 8.8 with the 32 spline axles is the standard since 2015 now but I think a 9.75 is still offered with a f150 on the HD payload / Max Tow PKG.

I felt the same with the GM 350 vs the 5.3 LS. The TBI 350 was better for towing since all the torque was just above idle.

 

[melk]

Bought from my neighbor 1 year ago. Original owner, he spent the first 20 years with it mostly camping in the California desert. My son has been driving it as his daily but I’m about to take it back over and get around to changing diff and trans fluid.

 

[1978elcamino]

View attachment 272683


View attachment 272682
View attachment 272684
View attachment 272685


Bought from my neighbor 1 year ago. Original owner, he spent the first 20 years with it mostly camping in the California desert. My son has been driving it as his daily but I’m about to take it back over and get around to changing diff and trans fluid.

Nice! A very unique truck. BTW, when the rear door cable ends give you grief and wont open, they make aluminum replacement pieces to fix it without replace the entire cable system. Cheap, easy and a good, permanent solution. Been there done that with my 2002.

 

[tcp71]

Torque is the reason.
From an owner of a new Coyote f150 that tows quite a bit I can say the 5.4 has better low rpm torque for towing.
I have used my fathers previous 5.4 to tow and IMO it did better. Is it possible that Ford thought the older 28 spline 8.8 was not up to task and decided the 9.75 would be a better fit? Maybe, idk.
I believe the super 8.8 with the 32 spline axles is the standard since 2015 now but I think a 9.75 is still offered with a f150 on the HD payload / Max Tow PKG.

I felt the same with the GM 350 vs the 5.3 LS. The TBI 350 was better for towing since all the torque was just above idle.

There are two versions of the 9.75 now. The normal, bearing supported version, and the heavy duty version, which is 3/4 floating. Apparently the 3/4 floating version drops the bolt holding the axles in.

The 3/4 Float 9.75” HD axle came on the 2021+ powerboost, hdpp and max tow trucks


https://www.f150ecoboost.net/thread...as-broken.91723/?post_id=1452539#post-1452539

 

[thastinger]

Never noticed a 7 lug, wow.

It was a strange time in driveline fitting. In 97-99 Ford sold a "Lite Duty" F250 which was badged as a 250 but looked like the 10th gen 150s, they all had 7 lug wheels. Ford did not have the Super Duty F250s ready until later in 99, when the SD250s came out they discontinued the LD250s that looked like 150s. During the same period of time, Ford sold 150s with basically the same running gear as the LD250s but with 5 lug wheels.