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Discussion Starter · #1 ·
What’s up goat family… Long post incoming w/ description and desire for help or recommendation of a shop near me

As the title states, I’m in Sacramento CA and desperately in need of a shop to take the goat to to have them check out my diff.

never had a single issue with my rear end since I bought the car in 2016

it’s an 04m6 with 68k miles. Kept in immaculate condition inside and out since day one

I changed the dif fluid w/ 1.8qts TorcoRGO and half the bottle of their TypeF FM @66k miles in February along with the trans fluid (first time for both in the 5 years I’ve owned)

when I changed both fluids, aside from normal lubricant breakdown, everything looked and felt fine..in fact, after replacing the trans fluid with fresh AC DELCO dex3 It shifted a little smoother and actually went into gear better than ever before


Out of nowhere, about a week and a half ago now, I start getting this low growling puttering noise what I had assumed was the clutch or trans/driveline …It got intensely progressively worse from Monday to Friday, going from barely noticeable to “oh shit I don’t think I can even drive it”

After this whole last weekend of having the car up on Jack stands (from Friday after work til currently right now) I ran it a million times in every gear, and reverse. Noise is completely non existent in neutral and only under load…

-Checked every link in the driveline, all flex discs/guibos
-Checked the connection from the trans to driveline
-Checked all the rear axle bolts on each side of each axle/stub/ all Allen bolts were tight as could be. No missing bolts or hardware ANYWHERE in the drivetrain
-No leaks anywhere (except a tiny brown spray on the exhaust pipes/perhaps from the pinion seal?)
-No play at all in the driveline, axles, wheels, anywhere at all that I can find—
-Center carrier bearing is totally fine and intact.
-Took apart both rear brakes, all the way down to the hub, cleaned everything put everything back properly

-Pulled both rear ABS/TC speed sensors in the rear, cleaned with maf/electronic cleaner.. reinstalled. Checked their small air gap between the sensors and the stubs… totally clean no debris, all 4 corners ABS wires/sensors are intact
(I’m mentioning the ABS stuff because amidst all of this , I now have an ABS fault light come on everytime I start the car and it will not go off)
-Changed ABS fuse in driver seat fuse panel
-Disconnected/cleaned and reconnected ABS module in engine bay

The only thing I’ve found through this entire checklist, was that when the rear wheels are in the air, spinning them freely there is a point where within that full rotation, it sort of binds up and almost comes to a complete stop unless you push really hard to make it spin again, then it spins again until that bind up point. Since the the dif carrier and both axles are obviously all connected, you feel the binding feeling on both sides when spinning the wheels freely, but I’m 99% sure it’s the driver side rear axle that is causing it.
When I noticed this at first, the common thought is a stuck caliper or maybe the brake shoes for the handbrake. This is why I removed all the brake components down to the hub yet when the car is in gear moving forward it is still totally there.
Im at a complete standstill at this point with the car… and not driving it (though it is my daily driver) because I don’t want to make anything worse nor is it even enjoyable to drive at this point.
I have no more ideas other than tearing apart the whole rear end and I don’t think I have the tools, time or patience to mess with something as sensitive as our Aussie rears .. though If I knew with certainty what the issue was, I’m sure I could actually do the repair. But I don’t..
Other than taking the goat to the dealer which is usually super expensive..but I do trust their work.
I’ve already had West Coast Differential , here locally, tell me they won’t touch the car, and aside from one or two more shops in the area I don’t know where else to turn.
Any help from you guys is sincerely appreciated and again sorry for the long ass post. Figured better get it all in one than keep posting with no reply.
I’ll attach a video below showing the noise

 

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Discussion Starter · #2 ·
Notice nobody has even read anything. so I’ll update a bit.
Pulled both rear axles. Pulled both axles stubs. The binding in the rear (which I’m assuming is the cause of the noises) seems to be related to the side adjuster bearings the bearings that each axle stub goes into. Or at least, that’s what I’m thinking as of right now … gonna attempt to take to a shop tomorrow. This has been a real headache as every other problem I’ve ever had with this thing (not many) have been so cut and dry I wouldn’t even need to post on here
 

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We have fearless gear down here in Fresno, they’ve been around forever. I wouldn’t go to a dealer.
I know it’s a drive but at least worth a call.
Hope you get it going soon.
 

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Discussion Starter · #4 ·
We have fearless gear down here in Fresno, they’ve been around forever. I wouldn’t go to a dealer.
I know it’s a drive but at least worth a call.
Hope you get it going soon.
Thanks for the reply my man. Took it to Jaws gear and axle today in north highlands. Gonna hope and pray I don’t have to spend 2 grand on a whole new dif and gears. I pulled all the axles and stubs and nothing looked fucked up. Did a fluid change 2k miles ago with torco RGO and typeF fm. Lost for words lol just started low growl grumbling a week or so ago then on the way to the shop this morning sounded even worse.
 

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Thanks for the reply my man. Took it to Jaws gear and axle today in north highlands. Gonna hope and pray I don’t have to spend 2 grand on a whole new dif and gears. I pulled all the axles and stubs and nothing looked fucked up. Did a fluid change 2k miles ago with torco RGO and typeF fm. Lost for words lol just started low growl grumbling a week or so ago then on the way to the shop this morning sounded even worse.
Hope so too report back when ya find out pls.
 

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Discussion Starter · #6 ·
Well figured I’d report back for those that care… turns out all the bearings in my dif were shot (pinion bearing both carrier bearings and the side adjuster axle stub bearings were going) …

well I drove the car that way for about a week getting progressively worse not knowing what it was til I had it on jackstands a whole weekend.. and still couldn’t find a diagnoses on my own.. (Pulled axles pulled stubs and the whole other check list I initially posted.. for a backyard “mechanic” I did as much as I could)

took the car to Jaws Gear & Axle (super nice high end rear end shop in North Highlands that also unfortunately for my rear end was a 20 minute freeway drive away. Instead of towing, I figured what the hell is one last trip anyway 🤷🏼‍♂️ Well about half a mile from the shop the puttering in the rear turned into an aggressive abrasive CLUNK/paddle board whap/grenade launcher explosion noise…I almost pulled over but was down the street…(excuse the inaccurate description humor but it was not pretty at all)

upon further diagnoses from all the bearings, my ring gear apparently had about 5 teeth sheered off and he said I was actually lucky I didn’t grenade the whole unit upon driving there (which it most definitely would’ve given any further driving…)


Mind you I also checked the fluid (2000 mile-3month old Torco RGO 85/140 w/2oz TypeF fm) during my initial diagnoses and it looked almost new still/ no shavings no flakes nothing … I imagine that changed by the time I got there.

so long story short I’m having them rebuild the whole thing, and theyre getting me a ‘new’ OEM 3:46 ring and pinion from a donor goat with like 20k miles, <he acquired it like a day after diagnoses from a wrecker up the street/and it’s warrantied as well through the wrecker> Shop owner suggested this over ordering an aftermarket or reman gear set as he said the OEM metals are much stronger and are just made better. His words so 🤷🏼‍♂️ If there’s anything I’d say I’m more unfamiliar with ..w/ my car or performance cars in general… it would be
Differential rebuilds and their bearings/pinion settings/seals
&
•Transmission rebuilds and or understanding transmission internals (autos specifically!)

The bill is around 2 grand, he said my LSD looked totally solid which surprised him, he said everything in it looked to spec but if I wanted that replaced as well that would be another $700.. I have his word tho (and in writing) that once I get the car back if I hear anything or feel anything out of sorts with the LSD aside from all the work they did, he’ll replace it at the same rate he already told me wouldn’t charge me more for a new diagnoses or rebuild.
That’s about where I’m at… I can post the invoice on here for any of you guys to pick at maybe or throw in your two cents. All feedback is honestly appreciated as this is my first time dealing with the rear on this car and is making me very reluctant to even do the minor mods I WAS gonna do for fear of messing with this finicky Australian Dana lol. (Wanted to throw a nice G force mount or billet anti hop mount on there, or at least a poly insert… now I’m skeptical to even touch it after this for fear of causing any potential issues)

I also have one last quandary with the gear oil, they’re going to use this Yukon Gear 80w/90 oil and “synthetic friction modifier” … when I get the car back, should I run this for 500 miles (if I have no issues that is) then swap it out for the torco??? Or maybe redline? It scares me that my rearend was in impeccable shape (that I knew at least) the first 65,000 miles I ran it with oem fluid til I swapped in the torco. Had no whines clunks or noises before the fluid change OR after until this whole thing like I’ve already stated… so it makes me nervous like did the torco have anything to do with it? If I never changed it would this have still happened? Or maybe I should’ve change it even sooner but never did?🤷🏼‍♂️ Either way I’d appreciate some feedback on this by anyone… these guys know their stuff and I trust them whole heartedly with the job but when I saw the oil specs and what not it just kinda perturbed me thinking “well fuck is this gonna fuck something else up now!?” 😂 thanks for reading my Ted Talk y’all let me know what you guys think
💪🏼 And lmk if anyone wants to see the invoice
 

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If I had more time I'd go back to every post about differential fluid and run a tally on how many people had either success or problems with various brands of fluid, and same for the weight. The general consensus when I read about it was that it probably didn't matter what brand, but most guys said to definitely run the 75w140 vs the 80w90 or whatever viscosities they come in, run the thicker instead of the thinner. And of course type F modifier, generally 1oz per quart. But idk, if these guys are saying that and you run thicker fluid and have a problem, idk what I'd do in that situation.
 

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Discussion Starter · #8 ·
If I had more time I'd go back to every post about differential fluid and run a tally on how many people had either success or problems with various brands of fluid, and same for the weight. The general consensus when I read about it was that it probably didn't matter what brand, but most guys said to definitely run the 75w140 vs the 80w90 or whatever viscosities they come in, run the thicker instead of the thinner. And of course type F modifier, generally 1oz per quart. But idk, if these guys are saying that and you run thicker fluid and have a problem, idk what I'd do in that situation.
dude I appreciate you reading and responding I know it was a little long. Just like to be full and concise when explaining stuff. I totally agree with everything you said… and if I’m not mistaken I think even in the freakin manual the OEM spec is 75/140 so not sure why they chose the 80/90.
And I totally agree with you that it’s like… okay what if I swap fluid then end up Fucking my 2000 dollar job up!! lol it’s such a headache … but
Either way… I’m thinking I’ll do what I initially mentioned and at 500 miles from when I get the car back I’ll go ahead and swap in either some torco or redline. Can’t go wrong supposedly with both (tho I still have my doubts) I don’t wanna run a thinner oil for a long time and end up causing any more damage. But then again what if they’re right (they do race car rearends lol) and we’re just speculating! 🤣
 

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dude I appreciate you reading and responding I know it was a little long. Just like to be full and concise when explaining stuff. I totally agree with everything you said… and if I’m not mistaken I think even in the freakin manual the OEM spec is 75/140 so not sure why they chose the 80/90.
And I totally agree with you that it’s like… okay what if I swap fluid then end up Fucking my 2000 dollar job up!! lol it’s such a headache … but
Either way… I’m thinking I’ll do what I initially mentioned and at 500 miles from when I get the car back I’ll go ahead and swap in either some torco or redline. Can’t go wrong supposedly with both (tho I still have my doubts) I don’t wanna run a thinner oil for a long time and end up causing any more damage. But then again what if they’re right (they do race car rearends lol) and we’re just speculating! 🤣
You will find a post here and there of guys who said they didn't have any trouble with the thinner gear oil, but you get the impression from most other posts and even guys responding to them that they just got lucky. Heck there's even a couple posts of guys saying that torco sucks. Right now I'm running mobil1 75w140 with 2 oz of torco type f fm and it's fine, no clicking, no noise, both tires spin in a straight line. So currently I'm of the opinion that any quality 75w140 with the proper ford type fm at the proper ratio is fine.

Maybe you should just tell the guy that there are tons of posts online about these specific rear ends that are adamant about using the thicker weight and see what he says.
 

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Discussion Starter · #10 ·
You will find a post here and there of guys who said they didn't have any trouble with the thinner gear oil, but you get the impression from most other posts and even guys responding to them that they just got lucky. Heck there's even a couple posts of guys saying that torco sucks. Right now I'm running mobil1 75w140 with 2 oz of torco type f fm and it's fine, no clicking, no noise, both tires spin in a straight line. So currently I'm of the opinion that any quality 75w140 with the proper ford type fm at the proper ratio is fine.

Maybe you should just tell the guy that there are tons of posts online about these specific rear ends that are adamant about using the thicker weight and see what he says.
Dude that’s what’s funny is bringing the 2 old school racecar rear end builders the millennial “hey man so I heard this online” lmao I actually prefaced our initial meeting with that and that was when the Jim dude (older of the two) was like “a lot of this stuff is the same to us I can bet ya if I put X oil with X modifier in there you wouldn’t know the difference” … sooo yea haha. But like I said, I actually have an oreily down the street with Castrol GL-5 85/140 rear gear oil for 6.99 a qt (might actually try that) and then they also had “Castrol 80/90w w limited slip differential additive” I’m assuming their friction modifier. I’ll prolly order the type F stuff from torco and just go with the Mobil, Castrol or if I find some nice redline. I’m stoked to get it back either way dude and hopeful everything turns out on a positive note. The weekend before I took it in we finished the putting in the headers so I haven’t even gotten to like feel em out yet lol
 

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As I typed that I was imagining the responses you might get but this is a little different than a typical I read it online situation. Just run the thicker oil and if it fails, swap the oil out before bringing it to them.
 

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my guess is their gear oil and FM will work, just not work well.

i would run it for a short time and drain/replace with 75w140 and use motorcraft xl3 or torco type F. or swap it out even sooner if you notice weird noises making turns at low speed.

i've ran thinner gear oil in GTO diffs and it... worked. nothing bad happened.
 
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