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- 2019 Challenger Hellcat Redeye Wide Body
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*.
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.
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.
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?
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*.
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.
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.
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?
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