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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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#2 · (Edited)
Studs in. Maybe I should have put the studs in after dropping in the center section to avoid damaging threads and raising my blood pressure? All I know is the Jawhorse was invaluable once again.


The center section is sitting flush now, right? Not quite. Don't try to force the bearing in. torque it down, loosen, then tap the bearings in.


Done, ready to go in.


Side by side comparison. The stock unit is pretty heavy at 80lbs with the mount and full of oil. I didn't weigh the 9" and housing, but let's just call it really smurfing heavy. 125ish sound about right? Thank you trans jack!


And voila, it's in. Yep, already managed to scuff up that nice powder coating :nonono:
 

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#3 · (Edited)
Overall install shot.


Closeup of the wrapped exhaust sections.


Driveshaft POV of exhaust clearance. All the wrapped areas are about an inch away. Glad I made the changes ahead of time!


Driver side axle/stub clearance is TIGHT. I should have built in more drop on that side when fabbing the h-pipe. It'll work for now, and I'll gain some clearance whenever I do longtubes and throw in the new motor and and trans mounts.


All done. Too much sun, but you get the point. As a word of caution, ground clearance is down significantly. The jack I used under the stock diff to put it up on stands got stuck under the new diff when I lowered it back down. Let's hope I never drive over anything more than 4" tall. Now to fix that droopy plastic panel.
 

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#4 ·
Looking forward to hearing whether or not you feel this is worth the $6000 investment. This is quite relevant to my interests currently, as I suspect I'm in for a new differential (again) myself.
 
#6 ·
The install looks great! I hope you dont mind but I'm going to put your install photo's on our facebook :)

Yea, the diff to housing bolts are pretty tight. It has to be dead nuts on (tight) to line everything up.
Maybe you noticed and looks like that was what you did but the instructions say to leave the stud nuts loose until you get the stubs in. When the stubs go into the housing and posi it lines everything up.
Then you tighten everything down.

Sorry about not having the fill cap in there..

Thanks
Chris
 
#8 ·
Nice thread! Looks good, I ordered a 9' from gforce as we'll just waiting, about 3 weeks out. Can't wait wait to get it installed myself.

The stubs look massive! You go with the 35's?
 
#10 ·
That's fine with me Chris, Facebook away! No worries about the fill cap, you got it to me just in time. And yes, I had the nuts loose when putting the stubs in. I tightened them down just to get the housing seated all the way, then loosed everything. The stubs and bearings went right in with some easy taps and all was good. Thanks again for all the help!
 
#15 ·
Yes, the 9" is physical larger then the GTO rear so it is going to hang lower.
Nobody has ever told us they have had a problem with ground clearance though. I think it's just something people notice that it's hanging lower and they automatically think it's going to be a problem but it isn't.

Maybe Chris should move the drain plug from the bottom side to (low) on the side of the housing. That would give a little more clearance and prevent the plug from being ripped-off if it does bottom-out on something.
I've thought about that but then again, nobody has ever said they actually did have a problem with ground clearance.
 
#16 ·
I need to upload my install experience. May help some others. Im also running a 3" spintech exhaust but I'm using a X pipe which gave me less clearance to the drive shaft so I had to turn down the mufflers on the spintech for me to feel safe. Welded up some new exhaust hangers and cut off the ones I wasn't using. Looks good!
 
#17 · (Edited)
Excessive Noise??

Ok, I need advice and input here. I finally took the car out today for a nice easy drive to start breaking in the new rear. I was expecting some additional vibration and gear noise/whine over stock, but this just seems downright excessive and/or BAD. Acceleration and constant load seems OK, just kind of loud over 50ish. Deceleration is about twice as loud most of the time. The transition between the two and coasting in neutral sounds and feels like someone taking an angle grinder to the frame. Downshifting is the same for the second when there is no load on the gears. I have a bad feeling this is not good. Will this go away as the gears break in? I'll change the oil tomorrow and see if there's any nastiness in there. Check out the video in the link below and you should get an idea, ignore the rattling sounds.


https://www.youtube.com/watch?v=Cu8RKPSw5hE&feature=youtu.be
 
#182 · (Edited)
Ok, I need advice and input here. I finally took the car out today for a nice easy drive to start breaking in the new rear. I was expecting some additional vibration and gear noise/whine over stock, but this just seems downright excessive and/or BAD. Acceleration and constant load seems OK, just kind of loud over 50ish. Deceleration is about twice as loud most of the time. The transition between the two and coasting in neutral sounds and feels like someone taking an angle grinder to the frame. Downshifting is the same for the second when there is no load on the gears. I have a bad feeling this is not good. Will this go away as the gears break in? I'll change the oil tomorrow and see if there's any nastiness in there. Check out the video in the link below and you should get an idea, ignore the rattling sounds.


https://www.youtube.com/watch?v=Cu8RKPSw5hE&feature=youtu.be
First off - to the op I hope everything gets straighten out for you. You have obviously spent a lot of time & energy on this.

I thank you for that youtube video. I got too know that sound all too well over the last few days.

Quick story - broke 4 teeth of my ring gear mid april on the first hit of the season at the track. Went into wheel hop and I thought I got out of it in time - yeah sure. The rear set up was 3.91 Aussie gears, Gforce stubs & half shafts, Harrop cover and a DSS drive shaft (the one with the hockey puck on the end of it).

In any event I sent my rear off to have new gears & a wavetrac installed. So the only difference was the wavetrac & now Motive Gears now vs the old setup. Started breaking them in properly - no highway for the first 150-175 miles, with several heat cycles. What a pain that is. Then I brought her up unto the highway and gently got her to 60-65 and let off - low & behold I couldn't believe the noise on the decel. Did it a few more times and same thing - then gears started to whine. Hit the gas and rumble went away - decel & back.

I sent a txt to my builder & a few other guys that deal with rears and their thought was that some of the fine metal during the breakin got into the wavetrac. So I flushed the system (was using Valvoline 85/140 conventional). The first oil had the same coloration as the ops - very fine metal - couldn't even feel it when I rubbed my fingers together.

Also checked everything underneath for tightness and it all seemed fine. Exhaust was tight as a drum.

After flushing went out again - same result. This time had my son with me and he said are you sure it's not the drive shaft? Didn't think so then - but given it was at speed I said it could be an issue.

Emailed DSS and they said they thought the build was fubar. Also to use Lucas 85/140 conventional gear oil. Haven't flushed it again - nor driven it.

Since this is beyond me - I am taking this to another shop and let them look at it. Given the car is raced a lot - who knows something might have shifted in the alignment of the drive shaft to the rear or the trutrac was much more forgiving. I will definitely have them check pinion angle and see if that could be the issue.

But again thank you for the video.

Steve
 
#18 ·
Make sure nothing is rubbing somewhere.

Sometimes the 9" rear make noise at first but quiet done after a few hundred miles.
We installed one and it sounded really bad. I called Strange and they asked us to put 500 miles on it and call back to let them know how it was doing.
We drove the car an hour and a half to deliver it to the customer and it pretty much quieted down before we got there.
A couple hundred miles later and it was nice and quite.
If for any reason it doesn't stop making noise no worries, Strange will warranty it and change the gears out.
Most times they are pretty quite right from the start.
 
#20 ·
hmm mine doesn't sound that loud. but I do have cogs whining right next to my firewall.
 
#22 ·
I've seen another 9" kit and and didn't hear anything like that. Have personal experience with another brands 8.8 kit, no such noise.

For gods sake, are you seeing sparks out the back? Are you dragging something? Is something loose?
 
#25 · (Edited)
Nothing rubbing, nothing loose, and there is still oil in it. There is some slop in the CVs, which I read before was normal for the level 5 axles. Nothing worse than stock anyway, and I'm not getting any clunks on takeoff or changing gears. I can turn the driveshaft easily by hand without getting any strange noises. I took these through the oil fill hole, anything look out of the ordinary? So far the gears have about 40 miles on them.





It looks like there is some surface scale or something wearing off the ring gear, but surely that wouldn't be causing all the noise.
 

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#28 ·
Nothing is rubbing. The grinding sound only happens when the gears are unloaded, i.e. coasting in neutral, letting off the gas right before the wheels start driving the engine, etc. I can modulate the sound while driving by coming on and off the gas ever so slightly, holding it in the "sweet spot", except not so sweet in this case. On a better note, the the whine while accelerating or maintaining speed has decreased. Above 75 or so, the gears go silent, though this could just be from increased engine and wind noise, or the frequency gets high enough to be out of hearing range.
 
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