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Rear Diff Cover

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Bahndvr

Bahndvr

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Will you be preparing a before and after test plan?
For a pre I'll have to figure something out to get numbers. Post I'm planning on installing a sensor to monitor.
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raab02

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Got mine installed last weekend.

Prior to that, a friend and I just completed a subframe-out project for him, so I was relatively comfortable with all the steps required. I used the following thread and video and found them both to be pretty spot on:

https://www.mustang6g.com/forums/threads/r-r-diff.96474/post-2116792
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https://www.youtube.com/watch?v=pI1-TCHlUDg


Since those two links above are essentially all you'll need, I'll just share some random install thoughts:

  • Like so many things, a lift and air tools would have made this job about 10x easier, but I used jackstands and a floor jack to muscle everything around.
  • I cannot imagine doing this solo. I suppose it's possible, but if you've got a good buddy, use their help. Plus working on cars with your car bros is fun. Bonus points if they also have an S550 and do track weekend with you.
  • I would HIGHLY recommend a sturdy, waist-height work surface to use for this. I had a giant Tupperware container to use, and it wasn't great.
    • Hanging the diff off the edge is how I drained mine, which worked pretty well, but...
    • At one point, it deformed enough so that the diff fell into the drain pan and slung gear oil all over the floor. Dumb mistake on my part.
  • Order the E-18 socket for the cover bolts. Those bolts are 'short' and it's easy for even the E-18 to slip off and round those bolts
  • Speaking of which, I reused my drain bolts, cover bolts, and temp sensor. Each got a good clean and a reapplication of sealant/ loctite where appropriate.
    • Obviously I cleaned and re-sealed the mating surface with new red sealant. I used a 2mm bead dead in the middle of the surface all the way around and gave it an hour or two before refilling. Afterward, mine looked exactly like the factory sealant around the edge and through bolt-holes. No leaks, so I feel pretty good about that.
  • I did order new driveshaft to pinion bolts. They had loctite and sealant installed already, along with the new c-shaped "keepers." Torqued in a star pattern to spec. Only got the car up to 95mph so far (on a closed course) but no wobbles from the driveshaft that I can tell.
  • I did not order new axle nuts, but you should. They are one-time use.My buddy and I debated about this, and did quite a bit of reading. Turns out that for track-bros, CV and wheel bearing failures are a fairly common issue. Many suspect the axle nut backing off is accelerating these failures, such that some choose to keep a spare CV axle, wheel bearing, and axle nut at events.
    • I re-installed mine, but only because the car will see maybe 100 easy street miles
    • I didn't have new on hand, so I did re-use mine by following the correct steps (98ft-lb, 45* turn beyond that) with new loctite.
    • I immediately ordered new ones to be installed before next track event. CCPZ-3B477-G is the current part number, replaces CCPZ-3B477-F, which replaced CCPZ-3B477-A as of this writing.
  • I refilled with 75W-90 BG oil from OP Mustang. Second time using this. First time had about 1 year and 3 events on it, and it still looked pretty good. Minimal sludge on the magnet.
  • I took this opportunity to add more exhaust wrap
    • Based on my wrap's instructions, I didn't double-layer over what I already had. I did extend it rearward, past the hangers and towards the mufflers even though this isn't all that close the the diff. THinking here being any heat radiating around the area would be good to contain if possible, since maybe the new fins could pick some of it back up? Either way, the fins will now be radiated into a cooler area hopefully.
    • Looking back I should have wrapped forward of the diff as well. As someone else said "the trans tunnel is a freaking oven." Having the exhaust off is the perfect opportunity.
  • We had a hard time reinstalling my diff. I still use the car on the street a lot so I didn't add any new bushings or bolts here and just re-used. It took quite a few tries of raising, lowering, torquing, backing out, etc to get it back in place. Looking back, we were worried about cross-threading these bolts in situations where we probably weren't going to cross-thread them. It just takes some muscle to get them back in.

Now some random other thoughts post-install:

  • Fluix was a great seller. Clearly done the research to design and build something we all needed. Quick responses, helpful, and proactive. A+
  • The product is of high quality. Zero concerns with fitment, etc. All points where it connects, mounts, or otherwise interfaces with factory stuff is perfect.
  • It does hang lower than the stock cover, obviously. It is not lower than the exhaust that I can tell.
    • As I said in another thread, this could theoretically contact something in the right (wrong?) circumstance.
    • I'm going to happily run it and I don't see this being an issue but wanted to mention it.
I can't work this thing hard enough on the street (and don't want to) to know enough about what kind of improvement I'm seeing. I'm really hoping this is enough to get me out of the warning and cooking fluid each event. That said, the fluid that was "cooked" (by getting the warning) looked pretty good, so.... who knows.
 

kz

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  • I did not order new axle nuts, but you should. They are one-time use.My buddy and I debated about this, and did quite a bit of reading. Turns out that for track-bros, CV and wheel bearing failures are a fairly common issue. Many suspect the axle nut backing off is accelerating these failures, such that some choose to keep a spare CV axle, wheel bearing, and axle nut at events.
    • I re-installed mine, but only because the car will see maybe 100 easy street miles
    • I didn't have new on hand, so I did re-use mine by following the correct steps (98ft-lb, 45* turn beyond that) with new loctite.
    • I immediately ordered new ones to be installed before next track event. CCPZ-3B477-G is the current part number, replaces CCPZ-3B477-F, which replaced CCPZ-3B477-A as of this writing.
I wasn't doing diff but was getting control arm and knuckles off recently.
My manual for '18 says 85 lb-ft and 30 degrees in second step. Manual for '15 which I also happen to have says 98 lb-ft and 45 degrees. Not a whole lot of difference but some - not sure where it comes from.
Axle nuts that were factory installed were actually sitting super tight, there was absolutely no way they would have come undone - I've used big Milwaukee M18 impact on highest torque setting to get them off and they did not come off easily.
 

FluiX

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Got mine installed last weekend.

...

Now some random other thoughts post-install:

  • Fluix was a great seller. Clearly done the research to design and build something we all needed. Quick responses, helpful, and proactive. A+
  • The product is of high quality. Zero concerns with fitment, etc. All points where it connects, mounts, or otherwise interfaces with factory stuff is perfect.
  • It does hang lower than the stock cover, obviously. It is not lower than the exhaust that I can tell.
    • As I said in another thread, this could theoretically contact something in the right (wrong?) circumstance.
    • I'm going to happily run it and I don't see this being an issue but wanted to mention it.
I can't work this thing hard enough on the street (and don't want to) to know enough about what kind of improvement I'm seeing. I'm really hoping this is enough to get me out of the warning and cooking fluid each event. That said, the fluid that was "cooked" (by getting the warning) looked pretty good, so.... who knows.
Thanks for the detailed install write-up and the positive feedback :). I am very glad you are satisfied with the quality of the product.

For those wondering about some more specs. The length the cover hangs lower than the OEM cover is 20mm or ~0.8". It is exactly level with the OEM exhaust. So in theory if you have never had your exhaust touch somewhere, the cover shouldn't either. But the risk exists of course in the same manner as it does on some AMG Mercedes and BMW M cars. Those actually hang closer to the ground. During the design I did keep in mind that some people will have lowered cars, so those will have the same risk as AMG and M drivers.

About the exhaust touching the diff cover fins that some people have asked. Unless you have some very "bendy" aftermarket exhaust, the exhaust will not touch the diff cover. The closest location on the OEM exhaust is on the side of the OEM cover. This is because the OEM exhaust does have a bend inwards towards the center of the car at that location. All big name aftermarket exhausts are rather straight compared to the OEM exhaust, so you should have even more clearance with these than with an OEM exhaust. The design of the FluiX diff cover purposely has a cut-out contour on the outer most fins, to give good clearance for the exhaust. I have marked this design feature in the attached picture. Going forwards below the car from the diff cover the clearance to the exhaust gets larger, so that should not be an area of concern.

iso_diff_full.jpg
 

FluiX

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Due to some shipping issues with DHL where it seemed that they lost the shipment, one US customer was sent a second cover. Now DHL found the lost cover and delivered it after two months. So this customer has a spare cover now. If someone is interested in purchasing this cover, it could be at your house within a 5 day shipping. PM me for details.
 

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Martin Schacht

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Nice :sunglasses:

Do you know what temp the ECU puts you in limp mode i.e. is the difference enough to keep it running normally ?

If the difference is enough to keep someone on track for their full session then I think these things will sell like hot cakes ... :like:

WD :like:
This has probably been answered elsewhere, from what I recall at last session at the track in February, Willow Springs Raceway, the Red Zone is 300 F, the ECU moves you to Limp Mode at 320 F...I could be wrong. The big point for me, "to keep someone on track for their full session then I think these things will sell like hot cakes." I had the dash warning come on in January on a cooler day..Limp Mode, damn!:frown:, off the track for me...drove around to cool things off. Before my next event in February, I had the exhaust pipes forward and aft of the diff, wrapped in tape used to insulate headers (From Summit). The tape seemed to provide some relief...never crept past 300 on a cool day, 70 degrees, 20 minute sessions. So if this finned diff cover fits a 2020 Mustang PP1, and can give me 30 degrees of protection, awesome. I'll have to have one.
 

FluiX

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This has probably been answered elsewhere, from what I recall at last session at the track in February, Willow Springs Raceway, the Red Zone is 300 F, the ECU moves you to Limp Mode at 320 F...I could be wrong.
...
So if this finned diff cover fits a 2020 Mustang PP1, and can give me 30 degrees of protection, awesome. I'll have to have one.
Limp mode should come on at 293 Fahrenheit. 30 degrees F may be a stretch, since that mostly depends on the ambient temperature and the load, but 20 degrees you should definitely see if you’re already closing in on the 293 sometimes.

Also to keep in mind is that if you come close to 293 with the cover, then without you could be over the limit by even more than 30 degrees, as the cover becomes more effective the higher the temperature difference to ambient gets. That’s a difficult test however, since the stock cars won’t let you go over the 293...

So far I have not received a feedback that someone went into limp mode with the cover :)
 

Martin Schacht

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Limp mode should come on at 293 Fahrenheit. 30 degrees F may be a stretch, since that mostly depends on the ambient temperature and the load, but 20 degrees you should definitely see if you’re already closing in on the 293 sometimes.

Also to keep in mind is that if you come close to 293 with the cover, then without you could be over the limit by even more than 30 degrees, as the cover becomes more effective the higher the temperature difference to ambient gets. That’s a difficult test however, since the stock cars won’t let you go over the 293...

So far I have not received a feedback that someone went into limp mode with the cover :)
This is some incredible information. Thanks you so very much. If I decide to keep the 2020 Mustang, so disappointed with this flaw, I will give your product a try. ....I have been a long time Porsche owner and never had overheating of the engine/Tranny as a problem. I am also looking at an "active" tranny cooler as a solution, BUT, it's $1,100 + labor. Ford should be ashamed of themselves for creating this problem.
 

mustang5o

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Got mine installed last weekend.

Prior to that, a friend and I just completed a subframe-out project for him, so I was relatively comfortable with all the steps required. I used the following thread and video and found them both to be pretty spot on:

https://www.mustang6g.com/forums/threads/r-r-diff.96474/post-2116792
favicon_96.png



Since those two links above are essentially all you'll need, I'll just share some random install thoughts:
...
Thanks for the great information.

Disregard. When I posted my reply the linked worked as expected. Not sure why it didn't work for me from your original post. Thanks again.
 

Martin Schacht

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My confession and Goodby: I bought the Mustang primarily for track duty, 6 to 8 weekend a year..Time Trials and DE. Damn! I should have done my homework. I admit I have always been captivate by the sound of a Mustang, especially the 5.2 Shelby GT Voodoo motor, but these cars were out of my budget, not so much the MSRP, but the $15,000 dealer mark was captivated. So January 2021, I settled for the 2020 Mustang GT 5.0 with Performance Package 1. Took it to the track with a local Porsche Club...it did turn some heads. Went to Buttonwillow raceway and the Mustang on Race Config 1 CW, turned a 2:09 first time out, about 3 seconds off the best time I had turned with a Porsche car, but..a respectable time. At Willow Springs (Big Willow), the car got up to 143 MPH on the front straight.....but it was too good to be true,. that damn diff overheating problem came to bite me on several occasions. I did wrap the exhaust pipes with header tape..that seemed to help reduce the diff temperatures. Another nagging problem, the brakes...they would overheat and begin fo fade.. I did have fresh high temp brake fluid in there and race pads. I had the Vorshlog deflectors, hadn't had the opportunity to install them my bad. I also has the 1mm titanium shims for the front calipers, hadn't installed these either.

When you have problems with brakes and an overheating differential, you have got some serious problems that take some serious money to solve. The Full Tilt Boogie active diff cooler is $1,200...or the finned diff cover, $750 + install. A "real" Mustang race buddy told me that I needed to invest in a $1,000 oil cooling radiator. Brakes: The rear 1 piston calipers are horrifically small. I could not find rear racing pads prior to doing 3 track days. When I pulled the pads to go back to stock, the front racing pads liked fine, the rear stock pads were down to 1mm.

Next steps, I added up the cost of the differential cooler options, both active and passive, the cost of an engine oil cooler the cost to put some decent sized calipers on the rear brakes,. considered the potential hassle of balancing the front to rear brakes...I simply gave up, sold off all the parts I had purchased to the Mustang, and sold the car in April. I went back to Porsche and bought a 2013 991.1 Carrera S, 3,200 Lbs, PDK auto trans and 400 HP. The Mustang was a fun adventure...sold it for $43,000 with 2,500 miles...pis about $50K for it with CA taxes...a $7,000 "bath", but it was fine while it lasted. On the 3 track days I had with the Mustang, the handling was first class. The front brakes were awesome until the fade kicked in, the creature comforts in the cabin were world class, and the exhaust note, hypnotic. It was a great car, it just didn't meet my requirements for a turnkey street track car. I just did 2 days at Willow Springs Raceway...the 991.1 Best time a 1:36.12....about 1 second better than the Mustang...but who's counting. For the money, the 2020 Mustang GT is a world class bargain...if one plans to track the car, notting that I had the diff overheating problems in very cool weather, this past January and February, potential over-heating problems in the diff as well as the brakes need to be considered. Invest the money in the diff cooler, beef up the rear brakes with larger calipers and balance the brake system front to rear, add race pads front and rear, add hight temp brake fluid, add an engine oil cooler...be prepared to upgrade the 10 Speed Auto cooler as well: It looks pretty flimsy to me. All in you'll invest $7,000 to $8.000....this is pretty damn cheap. Of course you need s set of wheels, about $1,000, run square...I ran 275/35/19 all around...could have gone bigger....but 19" 275 are plentiful and cheap....well maybe not so plentiful now with the tire shortage.. The handling of my car was incredible. I am so glad I didn't piss away money on a race suspension or lowering the car. Performance Package 1, is more than adequate for track duty...I experienced NO oversteer, NO understeer...and I pushed that car as hard as I could. Below is a pic of my new ride....there is a special car out there for everyone, be it a Mustang, a Porsche Camaro....
O.Z. and Re-71R.jpg
 

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hlh1

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Great write up. PM sent.
 

Martin Schacht

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Great write up. PM sent.
Got the PM....I did a data dump on you...IMHO, my former 2020 Mustang GT Deluxe PP1, was a fantastic car. The handling on the track was super. My only bitch is the cooling of the diff, and possibly the engine and the tranny. Didn't have problems with the last two, but the overheating diff was a problem. It can be cured. but I was not willing to put our the $$$ and effort to do this with an active radiator from fulltiltboogie.com . In my opinion, Ford was remiss in hinting in their promotion of the car, that is is 100% track ready as delivered. With the diff flaw, that's just not true. They provide a "Trail" mode, but be careful using it. I won't forgive them for that..it cost me some $$$$

The sound of the Mustang 5.0 car is intoxicating for those of us that love the 5.0 Coyote sound. But, in the end, I was more comfortable running Porsche TT events in a Porsche...BTW, the Mustang and I did kick some Porsche butt over the 3 track days we did. I was only passed once or twice, and that was but a Shelby GT 350. Keep the faith!!!
 

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Excellent well thought out posts and data from guys that also Track their cars is invaluable! I'm only in my 2nd season with my '18 PP1 car and agree that the rear diff is the achilles heel of the S550 platform on track. Having said that, as you mentioned the platform has many overall strengths. I'll be ordering the finned rear diff cover from Ish and upgrading my radiator to a triple pass unit from Kenny Brown before heading back out on track (Putnam Park and NCM). I'm going to invest in the platform and stick with it, in hopes of solving these issues and passing a lot of Vettes and Porsches out there.
 

Martin Schacht

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Excellent well thought out posts and data from guys that also Track their cars is invaluable! I'm only in my 2nd season with my '18 PP1 car and agree that the rear diff is the achilles heel of the S550 platform on track. Having said that, as you mentioned the platform has many overall strengths. I'll be ordering the finned rear diff cover from Ish and upgrading my radiator to a triple pass unit from Kenny Brown before heading back out on track (Putnam Park and NCM). I'm going to invest in the platform and stick with it, in hopes of solving these issues and passing a lot of Vettes and Porsches out there.
FWIW: Re. the finned diff cover, when you look at where the fins are located, on the leeward side of the diff out of the airstream, and the fact that installation is far from simple, were it me noting I sold my 550, i'd for sure do the Kenny Brown radiator and add the www.fulltiltboogie.com active radiator for the diff. It's about $1,200 and looks to be about 5 hours of labor to install. The S-550 has "good bones:", it simply needs its fluids cooled for track use. Stay cool!
 
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Bahndvr

Bahndvr

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@raab02 what gasket maker did you use?
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