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Gforce 9" kit installed!

31K views 216 replies 38 participants last post by  Gforce1320 
#1 · (Edited)
Long post, so bottom line up front: it's in! There were some issues, but nothing major. I was out of town this weekend so I've only driven it from one garage bay to the other so far, but I'll take it out tomorrow for some nice easy break-in. See the pics with comments.

Finally! The last of the parts arrived this past Wednesday and I spent two days doing the install by myself. This is the follow-up to my other two threads, the first debating on a rebuild vs the kit: http://www.ls1gto.com/forums/showthread.php?t=639737&highlight= and the second modifying the exhaust after realizing my Spintech would not fit as is: http://www.ls1gto.com/forums/showthread.php?t=649378&highlight=.

Day one was spent removing the stock drivetrain and prepping the diff and housing. Other than the diff to cradle bolts being a PITA, everything came out easy enough. The doubled up wrench method worked great, just not a lot of room to work in there. A transmission jack made the removal and install so much easier.

The biggest headache with assembling the diff was that the studs in the housing didn't match up with the center section as well as expected. After I put down a bead of gasket maker, I expected the center section to drop right in. Nope. It got hung up on the studs. Wrestling the 50 or so pound center section on and off the studs was not fun. It eventually took some light "persuading" to drop down flush, but not without leaving its marks on the threads of the studs. I also had to torque down the nuts to get it to seat fully so I could get the stubs in. I loosened the nuts, tapped the stubs in, torqued the stub retainers, then re-torqued everything back down. Assembly complete.

Aside from halfway rounding one of the axle bolts and the driveshaft u-joint not wanting to slip right in to the yoke, everything went together smoothly. Due to clearance, I ended up wrapping the crossover and the mufflers in header wrap just to be safe. We'll see how long it actually stays on. I'll eventually bit the bullet and buy 3" tailpipes ($500 from Spintech), but for now 2.5" pipes with leaky reducers and clamps will have to do. I wish I had gotten some measurements for the stubs before I made the new h-pipe. I was focused too much on driveshaft clearance, and as a result, driver side tailpipe to stub/axle clearance is very tight. I'm confident it won't hit after aggressively moving the pipe up and down, but still. Damnit. Either way, exhaust to expensive, heat sensitive carbon fiber driveshaft is great now, and the header wrap should only help.

One final note and a big thank you to Gforce Engineering. I called them several times throughout the install to ask questions and they were a great help. And when I realized I never received the oil fill plug, they overnighted it to me, no questions asked. I called them just before 5 their time Wednesday and had it in my hands just after noon the next day. Thankfully Kansas is closer than Japan. Awesome customer service! Enjoy the pics.
 
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#31 ·
Pretty frustrating, huh? Only difference is mine is a brand new unit built by professionals at Strange Engineering... If I'm not dead tired when I get home (first night on night shift), I'll taker her for a spin and change the diff oil. The oil looked pretty clean when I checked it the other day, but maybe there're some metallic goodies hiding at the bottom.
 
#33 · (Edited)
So how much heat is a diff supposed to generate under normal vanilla driving conditions? I went out for another 30 miles or so this morning of back road driving, mostly between 45 and 75mph with one moderate pull through the gears up to about 85. When I got underneath the car to change the diff oil, I noticed it was hot. Like touch it for more than one second burn you hot. This could explain why the car feels sluggish putting around through the neighborhood, and why the car decelerates in neutral much too quickly. Too much friction and drag. Anyway, this is what the oil looked like after about 100 miles of driving:


It looked like some puke shade of metal-flake paint. I taped a strong magnet to the bottom of the container and let it settle for about 30 minutes. There were still lots of little sparklies suspended in the oil when I dumped it, but this is what collected at the magnet:



There were no chunks of anything, but there were visible flakes. I'm guessing the black sludge is from whatever surface "scale" is coming off of the gears. That scale looks like it's acting as a marking compound of sorts though. I took some more shots through the fill hole and I'm wondering if there is too much pinion land to ring root, and vice-versa, contact happening. I'm certainly no expert, but gear contact where there shouldn't be any would explain the metal particles, excess noise, excess vibration (oh yeah, there's rumbling vibration too. Acceleration through 20-30 makes my mirrors useless) excess heat, and excess drag. Am I way off here?




See all that crap at the bottom? I don't like it. Or is this what normal ring and pinion break-in looks like?
 

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#35 ·
I'm in the same boat. It did quiet somewhat after about 3000 miles (drove on Hot Rod Power Tour) but it's still noisey as hell. Much better at lower speeds but cruising is annoying. Spoke with Strange and got an RMA to send back to get fixed. This video was taken after it quieted down a bit but is still loud 60mph+

 
#36 ·
I'm in the same boat. It did quiet somewhat after about 3000 miles (drove on Hot Rod Power Tour) but it's still noisey as hell. Much better at lower speeds but cruising is annoying. Spoke with Strange and got an RMA to send back to get fixed. This video was taken after it quieted down a bit but is still loud 60mph+

http://m.youtube.com/watch?v=7r7h_A_JA9A
That's very noisy too... You know Moser only recommends: 75W90 Motul Gear 300 (100118) or 75W140 Motul Gear Competition (101161) in their Wavetrac differentials. Maybe you should try it.
 
#37 ·
I don't have a Wavetrac
 
#39 ·
It is a internal failure within the s strac. I went thru probably 4 or 5 warranty claims last year on mine. Ditched the s trac for a spool and I couldnt be happier. Gforce is awesome to deal with unfortunately he has no quality control over the stuff coming out of Strange's shop. There are other options out there for a 35 spline locker to fit a 9" rear end.

And there is no fluid that is available to correct this noise. I wasted hundreds of dollars on fluids trying that game. The s trac is a shit unit if you ask me.
 
#42 ·
IF you decide to drive it again, take some temperature readings. Here's an excerpt from my thread regarding my temperature readings during break in.

"I went out 10 minutes one-way and back. Immediately put the car on the lift and grabbed my handy dandy infrared thermometer and checked temps. Left and right carrier bearing 152. Pinion bearing 155. Harrop cover 85. Bottom center of diff unit 152"


Sent from AutoGuide.com App
 
#43 ·
I had some downtime at work last night so I researched how a helical gear posi actually operates, and it got me thinking about oil quantity. I couldn't find the exact answer to "should a helical gear posi be partially submerged in oil?", but my instinct says probably. Looking at one of the pics on the first page of this thread, the oil level sits just below the helical gears. Granted the car was at a slight angle on stands, but I don't think being flat would've brought it up much. Some older 9" install threads used the (at the time) recommended 2 1/2 quarts, whereas my install instructions only called for 2. Chris said in one of the older threads filling up the housing using the oil fill port in the Strange center section takes 3. Shouldn't the oil level sit at the designed level? It seems odd to me that it wouldn't. And while it may not be the causal factor of my issues here, I'd think it certainly contributes. Not enough oil = more friction = more hot = more bad. I'm going to add more oil to the diff and see it that changes anything. Thoughts?
 
#51 ·
Gforce 9" kit [Un]installed...

Yep, it's back out. Surprisingly it didn't take as long as I thought it would this time. I only had to remove the tailpipes, the rest of the exhaust stayed on, and the driveshaft and axles were disconnected and held out of the way with bungies. Given the amount of struggle it took to get them together, I figured it would be way easier to separate the housing from the center section by removing the studs from the housing first. Tap a razor blade between the two in a few spots, wiggle in a screwdriver, then add another and work your way around. Got it cleaned up, boxed it up, and sent it off to Strange.

The oil looked better when I drained it this time than last time (about half the miles on it too), but I also put a magnet in the drain plug this time which definitely helped. Instead of looking like puke metal-flake, it was more like a caramel metal-flake. Here's the drain plug:

Still lots of badness in there.

And here's what I suspect might be the issue, though I don't have the technical expertise to explain why. Gear contact where there shouldn't be any, both on the ring and pinion:


The top/face edges of the ring teeth are worn on both drive and coast side, from heel to toe. I couldn't see all of the pinion, but you can see in the pic where it's getting worn. The "trailing edge corner" is the most heavily worn, and all the face edges look like those on the ring. In all my googling of good and bad tooth contact patterns, I haven't found anything that looks like this. Gear gurus, what say you?
 

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#55 ·
Fedex delivered the diff to Strange this morning, so hopefully I'll have an answer for all this in about a week. If nothing else, I'll have a newly rebuilt center section. Oh, and the diff packed in its plastic tote inside a cobbled together box weighs 89 pounds, just in case anyone was wondering.
 
#56 · (Edited)
I misread your shipping statement. Let us know when you get it back.

I was going to send mine out today but I have an event this weekend and another next weekend. So I'll send mine out the following week with hopes of getting it back within a week or so.

I decided I'm not messing around anymore and am just going to go full spool and be done with it. I can't afford the downtime.
 
#57 ·
Reinstalled

After three weeks of waiting, and a day and a half of Fedex losing the package 10 miles from my house in a distribution warehouse (Grrrr... had to sweet-talk my way in to pick it up), the diff is back together and installed. First impressions- it's better than it was. The accel and driving whine is minimal as before, the decel whine/howl is gone, but the no load/coasting grinding/grumble IS STILL THERE, though not as bad. Like before, I can only speculate why. My only option at this point is to keep putting miles on it and hope it gets better, because I sure as shit don't have the time or desire to keep smurfing with it. I was told the gears were going to be replaced, but it looks like they only replaced the ring gear. Kind of annoying, but they're the experts I guess. I also can't figure out why the car rumbles and vibrates so much accelerating and decelerating in the 20-40 mph range. Above that it's nice and smooth, so I'm assuming it's not a driveshaft misalignment issue.

So far I've put about 150 miles on the gears. I'll probably change and check the oil for metal particles at 250 or 300 miles. Fingers crossed. Unrelated, I also installed a new Redline shifter boot to replace the dry, creaky stocker. So much better.
 
#58 ·
After three weeks of waiting, and a day and a half of Fedex losing the package 10 miles from my house in a distribution warehouse (Grrrr... had to sweet-talk my way in to pick it up), the diff is back together and installed. First impressions- it's better than it was. The accel and driving whine is minimal as before, the decel whine/howl is gone, but the no load/coasting grinding/grumble IS STILL THERE, though not as bad. Like before, I can only speculate why. My only option at this point is to keep putting miles on it and hope it gets better, because I sure as shit don't have the time or desire to keep smurfing with it. I was told the gears were going to be replaced, but it looks like they only replaced the ring gear. Kind of annoying, but they're the experts I guess. I also can't figure out why the car rumbles and vibrates so much accelerating and decelerating in the 20-40 mph range. Above that it's nice and smooth, so I'm assuming it's not a driveshaft misalignment issue.

So far I've put about 150 miles on the gears. I'll probably change and check the oil for metal particles at 250 or 300 miles. Fingers crossed. Unrelated, I also installed a new Redline shifter boot to replace the dry, creaky stocker. So much better.
Wait...so they left the old pinion and replaced the ring gear? Isn't this a huge no no...?
 
#59 ·
That's what I thought. I could be mistaken, but the wear marks on the pinion looked very familiar. Hell, wear marks at all indicate it's not a new pinion. But hey, what do I know? Maybe that's normal wear for a pinion gear and they figured it didn't have enough use to negatively affect the new ring gear. At any rate it's much better (so far) than the original setup.
 
#60 ·
Give'ErTheGoat! , can you please continue to update us about your rear gear noise. I am holding out on pulling the trigger because of what i have read so far on this setup. All parts in this package are greatly package but gear whine is something i am not going to tolerate when you spend that much money on the kit.

It does not make sense why they didn't put new gears into the pumpkin when you sent it back with all those harsh marks on the edges. Did you sent them the pictures of the fluid?
 
#61 ·
I hadn't sent Strange any pics of the oil as I assumed Gforce was communicating with them, and the wear would be obvious to the builder. I'll do more driving tomorrow, check out the oil, and report back. I don't know why they would use the same pinion gear other than maybe they determined it wasn't causing the issue. I'm withholding further frustration until I put more miles on it since it is much better thus far. Granted it should have been perfect from square one, but there's nothing I can do about that right now.
 
#62 · (Edited)
I spoke with Mike at Strange earlier today. He said there's pretty much no way they would've used the original pinion gear since they come as a set. He also said they bevel the edges of the pinion and sometimes the ring gear during setup to help reduce noise, so maybe that's what I was seeing, and maybe the original pinion had been beveled similarly as well. So maybe I jumped the gun on that one, but this is what it looked like after the rebuild:


I also did an oil change today after about 250 miles of easy driving. The oil looked much better this time around, but there was still a good amount of metal sludge on the magnet. They are new gears though, so some is to be expected I suppose.




The ring gear itself looks infinitely better than the original did even after just 100 miles. Compared to the photos earlier in the thread, at least something here is right.


I sent Strange the videos I took earlier of the noise to get their insight. Mike had never heard of anything like this before. He did say however that the redesigned S-trac requires slightly shorter axle stubs, and if I got the older, longer ones from Gforce, it could cause some weird loading on the helical gears, possibly causing the noise. Kong at Gforce said they made the switch to the shorter axles well before I placed my order though, so I guess that idea is out the window. So at the end of the day, no one still knows anything...
 

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#63 · (Edited)
If you don't mind me asking, What was the gear ratio in your pumpkin?

If i do buy this setup from G Force, i was looking to go at least 4.10's with my 6 speed. The cam in my car does not feel like it is moving the car until about 3000-3200 rpm, so i want the gearing behind it. My goat is not a daily driver so i am not worried about the fuel economy.

The gears definitely looks better at this time. How many times do they recommend you to change the fluid? At what intervals? keep us posted please!
 
#64 ·
I've got 3.70s in mine. They recommend changing it after the 500 miles break in to remove any metal particles and other junk that might be in there, then normal intervals after that. I did it this soon to compare it to the oil from last time. It was much cleaner, but I did have a magnet in there the whole time too. Hopefully I'll hear back from Strange today and talk to the guys at Gforce again. Something is not right, and so far no one knows why.
 
#65 ·
Guess what I dropped off at Fedex today?

If you answered "Ian's soul", you're partially right. The guys at Strange and Gforce have no idea what could be causing the noise and vibration. Could be the posi, could be bearings, or it could just be my bad luck. I disconnected the axles and ran it on stands today to rule out the CVs (still made the grinding noise and vibration), and the stubs had some wobble to them. I would call it a significant amount, but that's just me. There was no play moving them by hand, but when rotating at speed, something about them wasn't straight. Could be a contributing factor, or it could be something misaligned internally.

So back it goes again. This time, however, I'm sending the entire assembled unit back to Gforce for them to inspect and rebuild. Housing, center section, stubs and all. They'll check it out, send the diff back to strange if needed, reassemble, hopefully test it out, and send it back to me. Which means I'll have the car back up and running in early December :)bomb:) when I get back from my government funded vacation to a hot and sandy part of the world. Maybe I'll put the stock stuff back in before flying home next week for my wedding, I've gotten pretty good at it by now.

To those of you still on the fence about going the 9" route, all I can say is the customer service from Gforce and Strange has been exceptional. Something in that 130lb chunk of metal heading to back to Kansas has something wrong with it, and they're doing everything they can to fix it. Nevertheless, the whole process has thus far been extremely frustrating and a waste of time. If the third time doesn't prove to be the charm, I may have to reevaluate my options. I'll continue to update the thread as I find out more.
 
#66 ·
hmmmm, i think i am going to wait it out and see what your end result is. Too much money spent to have this happen. This is a lot of work, taking parts on off and not counting the rear end fluid wasted and the car being out of commission.
Have a nice vacation and keep us posted. thanks for a providing such a informative thread.
 
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