Gforce 9" Rear End Install Tutorial Writeup
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2004-2007 Cadillac CTS-V General Discussion Discussion, Gforce 9" Rear End Install Tutorial Writeup in Cadillac CTS-V Series Forum - 2004 - 2007; Ok so I finally got my Gforce 9” rear end installed and took many pics on the way. It probably ...
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    lollygagger8's Avatar
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    Gforce 9" Rear End Install Tutorial Writeup

    Ok so I finally got my Gforce 9” rear end installed and took many pics on the way. It probably looks way more involved than what it really is, but it wasn’t that bad if you aren’t a rookie to working on cars. There is some cutting and welding that needs to be done, and maybe some fab work to your exhaust (depending on type) so make sure you know that going in. My buddy and I did this over the weekend on jackstands and plenty of tools. Grab the popcorn, and let’s do this……

    Tools you'll need:

    24mm Socket (Front Cradle Bolts)
    21mm Socket (almost all bolts/nuts on knuckle are this size)
    21mm Gear Wrench (Nice to have)
    34mm Deep Socket (Spindle Nut on Hub)
    18mm socket (Caliper Bolts, driveshaft adapter bolts)
    19mm wrench (new driveshaft to output shaft adapter bolts)
    10mm alllen wrench (Diff Drain, brake line holder )
    Long 1/2" Breaker Bar
    Long Pry Bar
    9/16” deep well socket (stud bolts to hold housing to pumpkin)
    9/16” box end wrench (bolts on axle retainers)
    5/8” allen wrench (must be allen wrench) for fill plug on Strange Pumpkin
    Impact Wrench
    Torque Wrench that reads up to 200 ft lbs.
    Beer of Choice

    Parts:

    Gforce Strange Pumpkin, 9” housing, Gforce Axles, Gforce Driveshaft, and all parts included in kit
    Black Permatex Ultra or Red Anabolic Gasket Maker (your choice)
    Red Loctite (for all bolt threads)
    1/8” or 3/16” flat metal stock (your choice)
    Sawsall and/or Grinding/Cutting Wheels
    Welder
    80w90 Non Synthetic Non limited slip Gear Oil (3 quarts)

    I take no responsibility for morons that hurt themselves. I didn’t get hurt during this install, but I’m not a moron. Lol.

    When placing your V on jack stands, make sure you don’t jack up on the cradle, since that entire assembly is coming out. Once you get a suitable place for your stands, get the wheels off. Let’s get the old axles and stock diff out of the way.

    Removing the old axles:

    Once you have your wheel off, Remove the Spindle Nut. This spindle nut is 34mm. You don't have to remove the Torx Bolt (T40) if you don't want to. But I did since it’s easier to see the axles splines behind the hub upon reinstalling.


    Look at the picture below. You need to place a drift punch or equivelant(I used the allen wrench) in between the slots in the rotor and the caliper. This will keep the rotor/axle from turning while you are cranking down on the spindle nut. *Move the punch/allen wrench to the under sire of the caliper when you are TIGHTENING the spindle nut.*


    Once you've removed the Spindle Nut, time for the caliper. The top bolt is longer than the Bottom Caliper Bolt

    Now it's time to remove the Ball Joint from the Hub Assy. It's a little hard to get at, but you won't need an extension. (pic shows with rotor removed)
    If it doesn't come out on it's own, coax it with a rubber mallet. It should seperate after a couple decent taps.


    Time to remove the Trailing Arm and Tie Rod.


    Remove the lower Shock Bolt from the Hub Assy. You might want to put a jack under the lower control arm so the bolt is easier to get out.


    Remove the lower bolt holding the Hub Assy to the Lower Control Arm.


    Now that everything is free, grab the Rotor and pull the Hub assy from the axle splines to seperate the two. If it doesn't want to come off, coax the axle end with the rubber mallet (or plastic side of the mallet) and it should come out.

    Here's a pic with all the Bolts out and the Hub Assy removed from the Axle.


    Now it's time to put your breaker bar in between the diff and the axle CV joint itself and seperate the two from each other. It doesn't take brute force by any means, all you are doing is getting the snap ring to let go. It will "pop" once you have gotten the two to seperate. (the fluid residue you see is from the vent)


    We’re going to leave the diff in the cradle for now since it’s much easier to take out while out of the car. We’ll just lower it with the cradle.

    Removing Exhaust and Driveshaft:

    Now it’s time to remove your exhaust. Once exhaust is off, remove the bolts marked (#2) in the picture. On the diff side are Allen Head bolts and are 8mm. (#1) is where the half shaft/drive shaft hit the floor board when my first diff broke. Put a jack stand underneath the "drive shaft" to keep the weight of the front bolts holding it to trans.


    The bolts on the trans side are 18mm. Gear wrench helps big time here.

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    lollygagger8's Avatar
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Removing Cradle and old Diff:

    Ok before we remove the cradle, we need to remove the parking brake cable, and disconnect the brake lines. The brake lines are 9/16” (use a flare wrench just because) and there’s a bracket on the passenger side that has (2) 10mm nuts on studs. Remove the bracket, and disconnect the brake lines. I used some rubber hose with screws in the end to plug up the brake lines…I suggest you do the same. The parking brake cable runs along the back of the cradle. I took a pair of vise grips and pulled on the cable until it came out of the bracket. Sorry no pics on these two things I was in a hurry.


    Now your V should be free and clear of the old axles, driveshaft, brake lines, and parking brake cable. Time to work on the cradle.

    Place your jacks on the cradle, and support it as evenly as possible since after the cradle bolts (24mm for the front, and 21 for the rear) come out, the entire cradle and diff are coming down. Tie up or secure your calipers so they don’t fall down since those are coming out too!
    Once you’ve removed the cradle, go ahead and remove the diff. The (3) bolts are 21mm. Once removed, your cradle should look like this….(looking at it from behind the car)


    WHEW!


    Mating Pumpkin, Housing and diff adapter:

    Now we need to mate the housing to the big beefy pumpkin and the diff adapter as well.
    Install the studs until they bottom out into the Gforce housing. When assembling the pumpkin to the housing, you need to install the axle stubs into the housing before you tighten the studs down. This aligns the axle stubs and housing with the pumpkin.
    Once you have done that, coat the sealing surface with your Gasket Maker. No real cork/rubber gasket hear since the surfaces are machined so well. Chris from Gforce says use Permatex Ultra black, but I used the red Anabolic Gasket Maker…..and mine didn’t leak 



    Once mated, I brakekleened all the excess off, and painted the bare surface black.

    Now grab the Strange pumpkin and lower it down on the Gforce housing and install the nuts on the studs. Chris recommends 33 ft lbs on these nuts. Once torqued you should look like this….



    You need to remove the nuts on the pinion support and install the Front Mount/Diff Adapter (the black circle with the red diff bushing in it). Orientate the diff adapter as shown here:


    front of car ->

    That billet yoke was something that Gforce sent but I used the Strange one that came installed on the pumpkin. Install the BMR bushing into the adapter and you are ready to install your new 9” rear end centerpiece into the cradle so you can mock up the axles and see where you need to cut the cradle.

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Mocking up and Cutting the Cradle:

    Now it’s time to mark the cradle where you are going to make your cuts. I used a white paint marker after I mocked up where the beefy Gforce axle CV’s would hit the cradle.

    You’ll have to cut a 1/2” or more off (depending on what size metal stock you choose) I chose 3/16”, so I had to cut just a tiny bit more. The cradle sort of curves down a little bit where it needs to be cut (you’ll see once you have it out) both sides need cut along the bottom of the cradles so the CV can clear it.

    *Cover or tape up the axle inlets on your new diff so you don’t get any flying debris inside it when cutting the cradle if you decide to leave it in the cradle!!! I removed mine, but it’s up to you*

    Here’s a few pics of marking, cutting, making a template and welded new pieces. I used a Sawsall for the up and down cuts, and a disc grinder for the sideways cuts.













    Now on the drivers side only:
    You actually have to cut the front (towards engine) wall of the cradle as well. Here’s a pic of that cut. (looking in from the drivers side wheel well) I was a moron and didn’t make this cut until after I put the cradle back in. Don’t make that mistake.


    **I also had to grind the lower control arm bolt head off about a 1/16” of an inch as well for the CV’s to clear. Chris from Gforce said they didn’t have to on their test vehicle, so maybe it’s a case by case scenario. You’ll find out once you get in there. You can see the bolt head right next to the cuts we made in the pics above.**

    Once you have the axles free and clear and you have welded up your new plates. Paint them so they won’t rust.

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Reinstall the Cradle/Axles/Suspension:

    Basically get it on two jacks, and evenly distribute the weight of the cradle (w/ new diff installed) and jack it up evenly. Have your buddy do one side and you do the other. Line up the “alignment pin” on the body with the cradle and make sure there’s nothing in the way before you put the cradle bolts back in. The front bolts are 24mm (tq to 195 ft lbs) and rears are 21mm (141 ft lbs)

    Hook up the brake lines (2 of them with a 9/16” flare wrench) and the bracket for them (2 nuts - 10mm) Connect the parking brake cable back up. Once you get that all in, oil up the axle seals with gear lube and push the axles into your new diff. There are different lengths on each axle so make sure you look.

    Important: The small diameter axle and the short axle stub goes on the drivers side. The big diameter axle and long axle stub goes on the passengers side.

    Once you seat them into the diff splines, it’s time to connect the axle retainers. They look like a small “C” and there are (3) 9/16” bolts to connect. Gear wrench helps here once you get the bolts in a little bit.



    Once you have that done, reconnect the new axles into the hubs. Reconnect the shock, ball joint, trailing arm, tie rod, and lower control arm to hub. Now it’s time to torque down those new axles. If you can’t get the axles to seat, get enough splines through the hub to thread the spindle nut on, and hit it with the impact. Once


    Installing Driveshaft /Exhaust:

    Here’s two pics of the front adapter how it mates the driveshaft to the output shaft of the transmission. Put the 3 big screws (19mm heads) on the trans side, and the 4 smaller screws (9/16”) on the driveshaft side.





    I got the 2 piece driveshaft. So you can install the driveshaft in halves. Reinstall the 2 OEM screws (15mm) that hold the carrier bearing to the frame of the car. Gratuitous shot of the beefy new Carrier Bearing…ain’t breaking that!



    Slide on the back half of the driveshaft on the front half’s splines and connect the u-bolts over the u-joint into the pinion and tighten the nuts with lock washers. (no pics of back half sorry I was getting excited and said eff it)

    Filling Diff/Break In Period:

    Now that you have driveshaft in, time to fill the diff! You have to use an allen wrench (5/8”) on the fill plug since the fill plug is located right next to one of housing to pumpkin bolts. You can’t fit a allen head socket in there….booo!

    Fill er’ up with about 2 ¾ quarts of your fluid of choice. Eaton doesn't recommend synthetics and you don't need friction modifier. That means that you can use basic Castrol 80-90W (I used Valvoline) or something similar. 3 qts is max fill capacity but 2.5 qty is plenty.

    Once she’s full, time to check out your handywork!! I left it up on stands, started the V up, and engaged the clutch to make sure the wheels were spinning before I reinstalled the exhaust. (wooowee it sounds mean lol) When everything looks good, reinstall the exhaust and let it down.

    The break in period is 500 miles. No racing no clutch dumps, etc. Does that suck? Of course. Does it need to be done? YES! You need to heat cycle your new 9” rear end. Gforce recommends 4 heat cycles of 30-45 minutes of normal city or mild driving, let cool down between cycles. Then do some mild everyday driving for 500 miles.

    Thank you, Goodnight!

    If I missed anything, my bad. If you have any questions, feel free to PM me or post up here and I’ll answer.

    I want to thank Chris at Gforce for making such a badass product for us V owners!!! He is a great guy to work with, and knows his $hit! I also want to thank my buddies Lance and John for all their help too. I couldn’t have done it without you guys! I’m going to the doctor’s now since I have carpel tunnel from all this typing.

  6. #5
    darkman's Avatar
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Great write up, Thanks.

    I may however, be a moron - I guess I need to get with SNL and see what the cost of being a moron is nowadays.

  7. #6
    rand49er's Avatar
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Some of the arrows suck.





    j/k Shane. Outstanding pictures and writeup. Truly outstanding!

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    CancerJCC is offline Cadillac Owners Connoisseur
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Great write up man! Now to embezzle 5k out of the checking account without the wife seeing...

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Quote Originally Posted by rand49er View Post
    Some of the arrows suck.
    Wow. That's an awesome write up! But, I do have to side with Randy, some of those arrows do suck.

    jk...awesome job and I cant wait to hear about how you like the 9"...(that's what she said)

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    GFORCE1320 is offline Cadillac Owners Enthusiast
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Great up Shane! As usual, I'll have to plagiarize it and call it my own LOL

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Quote Originally Posted by darkman View Post
    I may however, be a moron - I guess I need to get with SNL and see what the cost of being a moron is nowadays.
    Give me a heads up before you head up to SNL. Its a 30 mile drive from my place. I'm pretty sure I owe you a beer or something.

    I think SNL has done the Gforce 9" on a few Vs. Definitely the worry free place to go.

  12. #11
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    one of the few threads on here deserving a 5 star rating
    on the vids post 500miles...

    +1 thank you because i will be making use of this thread one day... already saved the entire page for offline use ::

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Hahhahaha....thanks fellas!

    Don't forget to get an alignment after this job!

    And now that I know what I'm doing, I'll offer installs at a good price
    thebigjimsho and thebigjimsho like this.

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Too bad you live in East Buttsqueeze...
    rand49er and rand49er like this.

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    Re: Gforce 9" Rear End Install Tutorial Writeup

    Quote Originally Posted by lollygagger8 View Post
    Hahhahaha....thanks fellas!

    Don't forget to get an alignment after this job!

    And now that I know what I'm doing, I'll offer installs at a good price

    Any updates on how this setup is working out?

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    wcryan is offline Cadillac Owners Connoisseur
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    Re: Gforce 9" Rear End Install Tutorial Writeup

    ^ yeah that

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