• Sign Up! To view all forums and unlock additional cool features

    Welcome to the #1 Dodge, Jeep and RAM Forum dedicated to FCA owners and enthusiasts. Register for an account, it's free and it's easy, so don't hesitate to join the SRT Forum today!


Per4mance DIRS and Differential Fluid Change

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
#1
Hello All,

As usual in my posts I'm going to give a lot of information. If you've felt I'm too detailed - or this topic doesn't interest you - do yourself and me a favor and skip this post.

At 1,800 miles in December, 2019, I drained the OEM rear differential fluid and replaced it with Royal Purple MaxGear 75-90W, with that friction additive needed for the limited slip differential. Easy, but I made a mess *grin*.

1652104075844.png

I installed the Per4mance Development DIRS differential brace in March, 2020. I have a four post lift and aside from having my wife hold a receiver piece in place above the rear axle for an anchor bolt I pulled it off. Two years and 9 HPDE days later at 6,000 miles I changed the fluid yesterday. An organizer for HPDE recommends owners change their differential fluid after every HPDE weekend. Heck if I know why that would be necessary...but sure I'm on board way earlier than the manual calls for sounds like a good preventative maintenance idea.

I'm posting this because I discovered that changing fluid with the DIRS brace installed was challenging and others might benefit from my experience. But also if anyone else has done this and knows of a proper tool, or better procedure, than what I did please share that information.

Background info - I got this sentence off either this forum or another one prior to my first fluid change - "Replace the differential fluid with Royal Purple Max Gear 75-90W fluid. Takes about 1 1/2 quarts. Drive the car for 20-30 minutes to warm up the fluid. Use a 5/16 inch Allen wrench to remove the fill plug nut FIRST, and THEN the drain plug nut. If you drain and then can’t remove the fill nut you can’t drive the car." Somewhere else I read an 8 mm Allen wrench fits too.

The DIRS on my car is this fine product - I don't think the information has changed. Like others I really like having it on the car.

https://www.getper4mance.com/produc...or-2015-newer-v8-chargers-challengers-300-rwd

I could see right after DIRS installation I would likely have a problem getting at the fill plug nut, and perhaps even the drain plug nut. Here is a picture right after installation. Note the vertical bolt head blocking straight line access to the fill nut, and also the narrow channel going to the drain nut. That channel is deeper than it looks. I wrote Bray at Per4mance Development after installation asking if they had identified a tool to get to that fill plug. Here was his response. "Both plugs will loosen with a straight Allen wrench with the ball end. The one behind the brace goes into a machined recess and there is a drainage path to divert the fluid down." He is correct. However, I have an assortment of Allen wrenches and not one of them was angled or length-correct to insert properly into the fill plug and be clear enough of the DIR assembly to turn. The best I could manage was a partial, angled insertion. To get the fill plug to "crack" open I had to use a crescent wrench on the end of a long Allen wrench. The worst case is a partial insertion like I managed could result in a stripped out plug. Was I stupid to proceed? Maybe (probably) but the Allen wrench's partial purchase felt barely enough - and I fortunately did not need much crescent wrench force to crack the plug. This was to be an "easy effort test" - and if requiring much force and risking stripping, then it would be a no go. But how do you know...until you strip the plug and then you know? Luckily that didn't happen.

1652099906638.png

For the first fluid change I had bought a Duralast brand 8 mm Allen Wrench tool for a 1/4 inch ratchet that fits both differential plugs - not the 5/16 inch mentioned in the post I read but it was tight. It made dealing with the exposed pre-DIRS plugs super easy. Here it is below with the fill plug stuck on it. I'll reference this later, but this is how it looked to re-thread into the fill hole.

1652100157218.png

Cutting to the chase, I needed this Duralast 8 mm Allen wrench attachment to replace the fill plug. And it wasn't easy. Diff. fluid is slippery. Again, if you're interested in the whole story read on...

So my two "DIRS installed" differential fluid change concerns were this first - that the DIRS attachment bolt going up to the rear axle blocks straight access into the fill plug nut. A straight Allen wrench simply cannot go straight in and have proper seating inside the plug. No ratchet tool I have could get in there with the Duralast 8 mm Allen tool attached. The only tool I had was an angled 8 mm Allen wrench - long enough to get the end away from the DIRS assembly and to get a crescent wrench on it to loosen the plug. And this angled Allen wrench's geometry would not line up the threads to reinsert the plug - I tried many times until I remembered I had that Duralast wrench in a tool box. The DIRS attachment nut screwing up the fill plug geometry can’t easily just be removed to provide straight access because it is anchored through a frame assembly into a “floating” threaded receiver piece provided by Per4mance Engineering. Post 2016 Challenger rear axle holes the DIRS utilizes were unfortunately not pre-threaded. So if this DIRS bolt is removed my conclusion was it would not be able to be reinstalled without a complete de-installation of the DIRS, including finding this now loose and on top of the axle frame receiver piece.

The second concern I had was the drain nut plug, which while having straight access through the narrow channel for proper insertion, after being unscrewed I worried might come off the Allen wrench end and maybe get sideways in there - and possibly stuck at the differential end of the channel. Rather than risk something going wrong and having to disassemble the DIRS I didn't attempt to remove the Allen wrench after unscrewing the drain plug - just let it lay inside the channel still properly inserted inside the plug. Fluid did rush out vertically in a channel just as Bray said when I got it loosened enough. When fully drained I simply re-screwed the drain plug into the differential - no problem getting those threads right.

With the DIRS installed there is no way to squeeze new fluid from a bottle into the differential. I used a two hose bottle pump (from Advanced Auto for $10 two years ago) to pump in fresh fluid until it started to come out the fill hole. Filling to the fill hole is technically more fluid than the manual calls for, but I did that in the first change and the car ran HPDE and 4,000 miles with no apparent harm done. The fluid had gotten a lot darker.

Now came the trickiest part - reinstalling the fill plug nut. The problem is both starting the threads without cross-threading, and, once properly threaded, screwing it in and tightening it (to 26 ft/lbs would seem almost guaranteed to strip the plug with the Allen wrench I had - either tightening or attempting to loosen in the future - so I need a properly seated tool and left it just hand tight snug for now). I could not get the threads started using that Allen wrench or just my fingers. I used the Duralast 8 mm mini-Allen tool, which was just short enough with the plug on it to fit inside the problematic bolt head and line up the fill plug threads. Using my left hand I brought it up to the fill hole and held it straight against the threads, then using my right fingers to reach over the DIRS I was able to turn it. Once started in the threads the plug can be turned from underneath by hand - with the Duralast quickly by spinning it, or more laboriously even with an improperly seated Allen wrench by inserting, turning a little, pull it out, rinse and repeat. I don’t think 26 ft/lbs is achievable with the long Allen wrench I had without truly risking stripped the plug - or if achievable, desirable - because of the future problem of loosening it for the next fluid change.

Which brings me to my burning question of the day for any of you who may have the same DIRS and done this and know of a tool which properly seats into the fill plug and can still be turned? What I see is needed for that fill plug is a 45 to 90 degree angled 8 mm, or 5/16's if that is correct, Allen wrench where the bend is enough to clear that vertical bolt, but not too long if sharply bent like if a 90 degree, to bang into any other part of the DIRS assembly. I know it might be possible to cut a 90 degree Allen wrench to fit, but the one time I tried doing (that for another use) my metal jig saw blade just laughed at me. A 45 degree might be the perfect angle.

A suggestion for Per4mance Development...more detailed information about how to do fluid changes with your DIRS? Tell us the right commercially available Allen wrench?

1652103899827.png
 


Last edited:

DGatzby

6000 Posts Club
Founding Member
Premium Account
U.S. Air Force Veteran
Donating Member
HFCOTM & HFCOTY
Member ID
#797
Messages
6,693
Reactions
42,593
Likes
402
City
SW Twin Cities
State
MN
Country
United States
Vehicle
2019 Dodge Challenger Redeye WB
#2
So @Finface a question. Wow, that sounds like a pain. Since it took me maybe 30 minutes tops, from unpacking the DIRS to complete install, (once Bray told me about the locking nuts above the cradle rail) why did you not just take it off, do the fluid change and replace?

But, thanks to your write-up, I’ll run several more days of HPDE before I will think my differential fluid has a problem.:p:p

FYI I think I changed my Blue Hellcat’s fluid after about three years and countless lap days just before I sold it. I do remember completely removing my ver1 brace to do that.
 


fubar569

1000 Posts Club
Founding Member
9 Second Best E/T
Member ID
#1073
Messages
1,145
Reactions
1,622
Likes
162
City
Bradford
State
PA
Country
United States
Vehicle
2018 Charger Hellcat
#3
I ended up.going to the hardware store and purchasing a new Allen key with the sole intention of making a tool.

I basically cut a straight piece just long enough to fit and still get a wrench up from the bottom between the DIRS. This allows me to do what I need to do.

Yes. It's an absolute PITA. No. There's no real easy way around it.
 


Idoru99

Active Member
Active Duty U.S. Navy
Donating Member
Member ID
#4871
Messages
302
Reactions
575
Likes
67
City
Dumfries
State
VA
Country
United States
Vehicle
2021 Challenger Redeye WB
#4
I ended up.going to the hardware store and purchasing a new Allen key with the sole intention of making a tool.

I basically cut a straight piece just long enough to fit and still get a wrench up from the bottom between the DIRS. This allows me to do what I need to do.

Yes. It's an absolute PITA. No. There's no real easy way around it.
I haven't done this yet, but if you were to cut an allen key to fit the fill plug and be inside that vertical bolt. Could you then use a crowfoot ratchet attachment to use on the allen key portion you're using? of course, this is all from pictures at work and not looking at my own diff and DIRS. Just thinking "out loud."
 


fubar569

1000 Posts Club
Founding Member
9 Second Best E/T
Member ID
#1073
Messages
1,145
Reactions
1,622
Likes
162
City
Bradford
State
PA
Country
United States
Vehicle
2018 Charger Hellcat
#5
That is basically what I did but I use a ratchet wrench instead. Serves the purpose.
 


Idoru99

Active Member
Active Duty U.S. Navy
Donating Member
Member ID
#4871
Messages
302
Reactions
575
Likes
67
City
Dumfries
State
VA
Country
United States
Vehicle
2021 Challenger Redeye WB
#6
That is basically what I did but I use a ratchet wrench instead. Serves the purpose.
That makes sense, I missed that you came up from the bottom. Just looking at the second picture in this thread, I was thinking about going in through the opening.
 


vortecd

Poster Club Hall of Fame
Premium Account
Donating Member
9 Second Best E/T
HFCOTM
Member ID
#1248
Messages
48,703
Reactions
156,611
Likes
402
City
Middleville
State
MI
Country
United States
Vehicle
2016 Charger Hellcat
#7
I had the DIRS on and off and back on already this year so an options is to just pull it off. It really doesn't take that long
 


Idoru99

Active Member
Active Duty U.S. Navy
Donating Member
Member ID
#4871
Messages
302
Reactions
575
Likes
67
City
Dumfries
State
VA
Country
United States
Vehicle
2021 Challenger Redeye WB
#8
I had the DIRS on and off and back on already this year so an options is to just pull it off. It really doesn't take that long
I had such a PITA time getting the vertical bolt through and biting into the insert, I NEVER want to do that again. That had me almost throwing tools. I was so frustrated with that part. [bash]
 


Last edited:

vortecd

Poster Club Hall of Fame
Premium Account
Donating Member
9 Second Best E/T
HFCOTM
Member ID
#1248
Messages
48,703
Reactions
156,611
Likes
402
City
Middleville
State
MI
Country
United States
Vehicle
2016 Charger Hellcat
#9
I had such a PITA time getting the vertical bolt through and biting into the insert, I NAVER want to do that again. That had me almost throwing tools. I was so frustrated with that part. [bash]
But now it fits so it should work fine :). I have had no issues the 3 times I have put it on
 


DGatzby

6000 Posts Club
Founding Member
Premium Account
U.S. Air Force Veteran
Donating Member
HFCOTM & HFCOTY
Member ID
#797
Messages
6,693
Reactions
42,593
Likes
402
City
SW Twin Cities
State
MN
Country
United States
Vehicle
2019 Dodge Challenger Redeye WB
#10
I had such a PITA time getting the vertical bolt through and biting into the insert, I NAVER want to do that again. That had me almost throwing tools. I was so frustrated with that part. [bash]
That was the bad deal for me. What I did not understand was the locking aspect of those, I thought I was cross threading, so initially it slowed me down. But like I said above, once Bray told me what they were, mine went in pretty easy. After reading his stuff and seeing others have a pain at it, I’ll take it off for the fluid change. I’ll just have Bray send me a couple of spare “nuts”.
 


Old Mopar Guy

2000 Posts Club
Founding Member
Donating Member
HFCOTM
Member ID
#1198
Messages
2,358
Reactions
6,564
Likes
302
City
Long Island
State
NY
Country
United States
Vehicle
15 Hellcat Challenger
#11
Guess us MY ‘15 guys got it good as far as that threaded crossmember goes. Good for me.
 


OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #12
So @Finface a question. Wow, that sounds like a pain. Since it took me maybe 30 minutes tops, from unpacking the DIRS to complete install, (once Bray told me about the locking nuts above the cradle rail) why did you not just take it off, do the fluid change and replace?

But, thanks to your write-up, I’ll run several more days of HPDE before I will think my differential fluid has a problem.:p:p

FYI I think I changed my Blue Hellcat’s fluid after about three years and countless lap days just before I sold it. I do remember completely removing my ver1 brace to do that.
DGatzby,

I freely admit it...I was worried that my removing the DIRS would wind up with me looking at a pile of parts on the floor *grin*.

It took me many hours to put it on because I am slooooooowwwwww. And that whole use dental floss to fish the receivers in place for the two bolts - that took me awhile and I had to call my wife with her nimble, smaller fingers to help. If there was a way around that I wanted to use it.

I am in awe of your (and many others here) mechanical skills - and willingness - to tackle what look to me to be daunting jobs. You built a motorcycle that won an award and can design hydroelectric projects, guys here build cars and experiment how to shave milliseconds off their quarter mile times. I read posts about bolt-on products for our Challengers and Chargers by people who like, and sometimes dislike, them and I have had fun - and gotten new skills - by tackling putting them on. It is a journey for me, but like poking around a pond full of crocodiles I am wary.

So far I haven't destroyed anything! But there is always tomorrow!

The Royal Purple fluid was a lot darker, but it was still purple and in good shape.

Finface
 


Last edited:
OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #13
I ended up.going to the hardware store and purchasing a new Allen key with the sole intention of making a tool.

I basically cut a straight piece just long enough to fit and still get a wrench up from the bottom between the DIRS. This allows me to do what I need to do.

Yes. It's an absolute PITA. No. There's no real easy way around it.
There is a small machine shop near my house and maybe they have something that can cut an Allen key for me. It would be nice if I could find a commercially made 8 mm Allen key, with a long section, where there is a 45 degree bend close to where it goes into the hex recepticle. That would clear everything and allow full insertion of the key into the fill plug, and allow for a wrench to leverage opening the plub if need be. I didn't look for one before posting. I could have answered my own question!
 


OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #14
That is basically what I did but I use a ratchet wrench instead. Serves the purpose.
Hmmmm, any chance you can post a picture of your cut Allen key and how the ratchet wrench is used?
 


DGatzby

6000 Posts Club
Founding Member
Premium Account
U.S. Air Force Veteran
Donating Member
HFCOTM & HFCOTY
Member ID
#797
Messages
6,693
Reactions
42,593
Likes
402
City
SW Twin Cities
State
MN
Country
United States
Vehicle
2019 Dodge Challenger Redeye WB
#15
DGatzby,

I freely admit it...I was worried that my removing the DIRS would wind up with me looking at a pile of parts on the floor *grin*.

It took me many hours to put it on because I am slooooooowwwwww. And that whole use dental floss to fish the receivers in place for the two bolts - that took me awhile and I had to call my wife with her nimble, smaller fingers to help. If there was a way around that I wanted to use it.

I am in awe of your (and many others here) mechanical skills - and willingness - to tackle what look to me to be daunting jobs. You built a motorcycle that won an award and can design hydroelectric projects, guys here build cars and experiment how to shave milliseconds off their quarter mile times. I read posts about bolt-on products for our Challengers and Chargers by people who like, and sometimes dislike, them and I have had fun - and gotten new skills - by tackling putting them on. It is a journey for me, but like poking around a pond full of crocodiles I am wary.

So far I haven't destroyed anything! But there is always tomorrow!

The Royal Purple fluid was a lot darker, but it was still purple and in good shape.

Finface
Glad it worked. Yep, I would have been ripping and unbolting and worrying about putting that brace on again later.:ROFLMAO: After about just one little Allen wrench did not work. But some of us are blessed with too many tools, right in our garages.
 


OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #16
There is a small machine shop near my house and maybe they have something that can cut an Allen key for me. It would be nice if I could find a commercially made 8 mm Allen key, with a long section, where there is a 45 degree bend close to where it goes into the hex recepticle. That would clear everything and allow full insertion of the key into the fill plug, and allow for a wrench to leverage opening the plub if need be. I didn't look for one before posting. I could have answered my own question!
I will answer my own question! I googled "allen key set with 45 degree bend".

Not an exhaustive search effort, but there are two brands I found with an 8 mm I found that look perfect. At US websites they say they are out of stock. This site in the UK has them (Nielsen company located there). About $10 for the set, plus whatever shipping across the Atlantic. It's an option, but I'll wait. I might wind up with so many tools in my garage I'll be tempted to build a motorcycle (nod to DGatzby).

I don't have a need for more than the one 8 mm, but this set may be in my future if I don't wind up trying to cut a spare hex key I have to fit.

Thanks for the replies.

https://www.ebay.co.uk/itm/193727664781
 


fubar569

1000 Posts Club
Founding Member
9 Second Best E/T
Member ID
#1073
Messages
1,145
Reactions
1,622
Likes
162
City
Bradford
State
PA
Country
United States
Vehicle
2018 Charger Hellcat
#17
Hmmmm, any chance you can post a picture of your cut Allen key and how the ratchet wrench is used?
If someone reminds me in about 8 days when I get home from work I'll try. I gotta do the fluid in mine anyway.

And install the BMR icebox. Doh.
 


OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #18
A neighbor came over and we discovered that with a 90 degree hexagonal Allen wrench (key) it is possible to fully insert the key into the fill plug from the top. By reaching over the same right side of the DIRS, looking forward. There isn't much room to rotate the plug, and it might depend on how the plug is oriented (where the angles are inside the plug) to get the Allen wrench inserted, but in my case it was possible to "snug" up the plug a tad more. We also had real trouble trying to get an 8 mm wrench in there - couldn't do it - but a 5/16 inch wrench was easier and did the trick.

The thing to keep in mind is that loosening it from the top might be tough if it is tightened too much.
 


Paladin06

4000 Posts Club
Founding Member
Premium Account
U.S. Army Veteran
Donating Member
HFCOTM
Member ID
#1080
Messages
4,662
Reactions
24,173
Likes
302
City
Clarksville
State
TN
Country
United States
Vehicle
2015 Challenger Hellcat/2019 Challenger Redeye
#19
That looks way to painful.
 


OP
Finface

Finface

Active Member
Member ID
#2078
Messages
319
Reactions
504
Likes
67
City
Morning View
State
KY
Country
United States
Vehicle
2019 Challenger Hellcat Redeye Wide Body
Thread Starter #20
That looks way to painful.
I agree.

Yesterday I ordered a set of what looks like 45 degree angled hex Allen wrenches from a UK Ebay website that contains an 8 mm wrench that will fit my 2019 Challenger's differential fill plug. It was $25 out the door - which included overseas shipping to Kentucky from England. My burgeoning toolbox runneth over...

https://www.ebay.com/itm/183036366341

When they get here in a week I'll report in this thread if the angled wrench will actually work.
 




Top