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 Post subject: Fox DHX 4.0 Rebuild
PostPosted: Sun Jun 09, 2013 2:31 pm 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
Posts: 3086
Location: Dallas, TX
If you directly linked to this thread, please visit our Fox Factory Service Information - Main Index for additional resources.



DHX 4.0 Rebuild

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Note: Some photos shown on this page may not actually be of this shock model. We reserve the option to preserve system bandwidth by substituting generic pictures whenever it's possible and appropriate.

Disassembly


1. Prepare your work area. Lay out a clean shop towel upon which to stage and organize your parts assemblies.

2. Wear your safety glasses (always protect your eyes), and use rubber gloves if so desired.

3. Remove the mounting hardware, and clean the exterior of the shock before starting its disassembly. This is a good time to make record of the eye-to-eye of the shock and travel. You will need this information later for looking up parts and the IFP setting.

4. Clean and inspect the bottom out bumper on the damper shaft. Also, make sure it's clean underneath.

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5. You will find a Schrader style air valve for charging the IFP. Unscrew the valve cap and release the air from the reservoir chamber.

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6. Remove the bearing housing and damper shaft with a one inch (1") open end wrench (turn counter-clockwise).

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7. Remove the bearing housing/shaft assembly from the damper body over an oil draining pan.

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8. Remove the reservoir end cap with a 24 mm socket wrench. You may need to hold onto the reservoir body with shaft clamps if it starts to unthread before the end cap does.

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9. Remove the IFP by griping onto the wrench flats with needle nose pliers.

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10. Remove the IFP bleed screw with a 2 mm hex key and 9 mm wrench.

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11. Clean the IFP. Replace the IFP O-ring, if necessary.

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12. Pour the remaining oil out of the shock into your drain pan.

13. Gently grip the damper shaft with the shaft clamps, and remove the piston assembly with a 3/8” socket wrench.

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14. Keep the piston assembly organized; lay it out expanded in order, on a clean shop towel.

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15. Inspect and clean all damper piston parts, that is, the piston, valves, and piston bolt.

16. Remove the shaft from the clamps, and slide the bearing housing off. Clean, and replace the bearing housing seal and shaft dust wiper with new parts.

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Note: Proceed with steps 17 through 26 only if you have problem issues with the boost valve in the reservoir.

17. Remove the screw from the ProPedal adjuster knob with a 2 mm hex key wrench. Remove the knob, and be careful not to lose the two steel detent balls and springs. Clean these parts and set them aside in a secure spot.

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18. Thread in the reservoir end cap into the reservoir body.

19. You can try to remove the reservoir from the reservoir eyelet without removing the decal, but often the decal will get damaged during this process. To remove the decal, warm it up a little to soften the adhesive; getting it warm to the touch works best. Peel the decal away from the reservoir, and then clean off the leftover glue with shop cleaner (Simple Green, isopropyl alcohol, or parts washer solvent).

20. Heat up the reservoir at the bottom, where the threads are located. The threads have Loctite on them from the factory, and the mild heat will soften the Loctite. Heat until it’s just hot to the touch.

21. Tech Tip: Clean the shaft clamps with isopropyl alcohol, and leave them wet. This action will help the shaft clamps grip the reservoir body. This sounds a little odd, but it really works (see the Wikipedia article Surface Tension and Energy of Cohesion.

22. Using ½ inch bar stock, insert this into the DU bushing bore and turn the eyelet counter-clockwise to unthread the reservoir body from the eyelet.

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23. You will need to clean the Loctite from the shaft and eyelet threads.

24. Remove the larger spring (i.e., the rebound check valve spring) from the inside eyelet cap.

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25. Remove the ProPedal spring (the smaller one).

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26. Using the FOX Racing Shox DHX hex socket wrench (PN 398-00-250), unthread the ProPedal adjuster.

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Make sure to thoroughly clean the threads of Loctite, and replace the O-rings if necessary.

Note: Proceed with steps 27 through 32 only if you have a problem with the rebound eyelet, or other damper shaft eyelet issues.

27. Clean the damper shaft with isopropyl alcohol, and also clean and spray the shaft clamps, and leave wet. Clamp damper shaft into vise with the alcohol-wet shaft clamps.

28. Heat up the top of the damper shaft to soften the Red Loctite. Do not overheat. Shaft should be just uncomfortably warm to the touch.

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29. Unthread the eyelet from the damper shaft. Do not allow damper shaft to spin in the shaft clamps; any damage to the shaft finish must be avoided.

30. Clean Loctite from the threads of both the shaft and eyelet.

31. Remove and inspect the rebound adjuster rod and O-ring. Clean or replace O-ring as necessary.

32. Remove and inspect the O-ring located inside the threaded damper shaft bore in the eyelet. Clean or replace as needed.

Now that you have all major components disassembled, it’s a good time to clean all the parts and inspect and replace the seal, O-rings, etcetera before you start the re-assembly process.

Re-assembly


1. Place the rebound check valve back into the bottom of the reservoir body and set it aside.

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2. Dab a little grease on the ProPedal adjuster parts (threads and hex rod)

3. Thread the two ProPedal female and male adjuster housing parts together all the way. Tech Tip: the threads on these parts are reverse (left handed). Also: insert the hex rod into the center of the housing, and next insert the hex rod into the assembly. Make sure to grease the hex rod also.

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4. Thread the ProPedal adjuster back into the reservoir eyelet by hand.

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5. Now test the ProPedal adjuster by using the ProPedal knob. You should be able to turn the adjuster knob approximately 3.5 full turns.

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6. With your FOX Racing Shox DHX Hex socket wrench, torque the ProPedal housing to 110 inch pounds (12.43 N-m) and set the assembly aside for now.

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Note: Skip steps 7 through 10 if you did not disassemble the shaft, rebound rod, and eyelet.

7. Insert the damper shaft rebound rod into the damper shaft. Make sure you have inspected the rebound rod O-ring, and replace it if necessary.

8. Before threading the damper shaft back into the eyelet, make sure that you have installed the O-ring into the bottom of eyelet threads, and that all threads are clean of old Loctite.

9. Drop two drops of Red Loctite #26231 onto the damper shaft.

10. Thread the shaft into the eyelet.

11. Place the bottom out bumper onto the damper shaft, and slide it up to the eyelet.

12. Lube the bearing housing seals and the DU with grease. Gently slide the bearing housing onto the damper shaft, all the way up to the bottom bumper.

13. Place the damper piston onto the damper shaft. Thread the bolt in all the way by hand.

14. Place the eyelet into soft jaw vise, and torque the piston bolt to 75 inch pounds. As you torque the piston bolt, your eyelet will also come into torque spec at the same time.

15. Test the rebound adjuster to make sure it’s moving freely. Set the assembly aside.

Note: Skip steps 16 through 19 if you have disassembled the boost valve assembly.

16. Inspect the reservoir, and make sure that all the old Loctite has been removed and the threads are clean. Re-check the O-ring at the bottom of threads of the reservoir eyelet.

17. Install ProPedal adjuster spring (small) and Rebound Check Spring (large) into the reservoir end cap.

18. Place two drops of blue Loctite #24241 onto the reservoir threads.

19. Make sure the rebound check spring, ProPedal spring, and rebound check valve are staying in place, as you thread the two parts together.

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Note: Skip steps 20 through 22 if you did not disassemble the ProPedal knob.

20. Place the two small springs and two small steel balls back into the ProPedal detent holes on the eyelet; a little grease will help keep the balls in place.

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21. Install the ProPedal knob (line up slot in knob to adjuster rod).

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22. Place a single drop of blue Loctite #24241 onto the ProPedal adjuster screw, and using the 2mm hex key wrench, thread in the screw until hand tight.

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23. Place the eyelet into the soft jaw vise and fill the reservoir up with suspension fluid (10wt). Fill up to just reach the bottom of the cap threads.

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24. Make sure you have inspected and replaced the IFP O-ring, if necessary.

25. With a 2mm hex key wrench, thread the IFP bleed screw into the IFP a couple of turns (the bleed screw will be removed again shortly).

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26. Slowly push the IPF into the reservoir. Push it down until you see the bottom of the last threads. You will see oil and maybe some air bubble up in the body. Remove the set screw, and set the IFP aside for now.

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27. Place the reservoir eyelet into a soft-jaw vise and wrap the body with a shop towel, to catch the oil in the final oil filling process.

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28. Top off the body with suspension oil.

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29. Push the bearing housing all the way down to the top out plate. Insert the piston and bearing housing assembly into the suspension oil in the damper body. Thread in the bearing housing all the way down with a 1” open end wrench.

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30. Using an IFP setting tool, push the IFP all the way down to the correct IFP depth for the shock. This will purge the suspension fluid and any small air bubbles out through the IFP bleed screw hole.

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31. Double check the IFP height, and thread the IFP bleed screw back into the bleed port. There will be a small amount of oil on top of the bleed screw. This is normal, and ensures that air does not enter the IFP chamber as you screw the bleed screw back in. A 9 mm open-end wrench can be used to hold the IFP steady as you torque the IFP bleed screw to 7 inch pounds (0.79 N-m) with a 2 mm hex key wrench.

32. Torque the bearing housing with a 1" crows foot wrench, to 35 ft-lbs. (420 in-lbs./47.45 N-m).

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33. Inspect the reservoir end cap and volume adjuster; grease and replace O-rings as necessary.

34. Thread the bottom out adjust control cap into the IFP chamber, and torque to 420 inch pounds (47.45 N-m).

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35. Pump the reservoir up with air to a minimum of 125 PSI.

36. Clean the reservoir with isopropyl alcohol, and replace the decal if necessary.

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37. Install the spring and mounting hardware as required.

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38. Return the shock back to your now-happy customer. Smile! :-]

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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 12:25 am 
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lurkin' kitty

Joined: Sun Mar 08, 2015 6:17 pm
Posts: 4
Hey man - first of all. Amazing tutorials. Quick question. I did an oil change on my 2011 Van RC. Went smooth and shock feels fine. But then I noticed the low speed compression knob is seized up. I never took that section apart so I'm perplexed. Any ideas what could have caused this?


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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 3:46 am 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
Posts: 3086
Location: Dallas, TX
Thanks. These tutorials are actually from FOX. I just adapted them for posting on the forum. :)

You only performed an oil change and the compression knob seized up? Well, I dunno...

If you reverse process and dissemble it again (like you did for the oil change), does the knob turn again (while disassembled)?

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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 6:44 pm 
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lurkin' kitty

Joined: Sun Mar 08, 2015 6:17 pm
Posts: 4
marpilli wrote:
Thanks. These tutorials are actually from FOX. I just adapted them for posting on the forum. :)

You only performed an oil change and the compression knob seized up? Well, I dunno...

If you reverse process and dissemble it again (like you did for the oil change), does the knob turn again (while disassembled)?



I noticed it wasn't turning when I had it apart. at first I thought maybe it wouldn't turn bc there was no oil in there or something so I proceeded and reassembled and no luck! I'll probably take it apart again sadly haha.

1) Any recommendations for what I could maybe look for when taking this apart?
2) In step 22 when you detach the resi, what is that bar for? Do you just use that for leverage? I thought the resi just unscrewed from the housing there?


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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 7:14 pm 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
Posts: 3086
Location: Dallas, TX
Step 22 of this tutorial? Or a different one?

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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 8:09 pm 
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lurkin' kitty

Joined: Sun Mar 08, 2015 6:17 pm
Posts: 4
This post, the line that starts with "use 1/2 inch bar stock". Is that bar just being used for leverage to unscrew the resi? I can't really tell why it's needed. Thanks!


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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 10, 2015 10:51 pm 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
Posts: 3086
Location: Dallas, TX
Ah, understand now. :)

Yes. They're using the bar to give you some leverage. In the reassembly it shows tightening it to 35 ft-lbs.

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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Tue Mar 17, 2015 12:53 pm 
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lurkin' kitty

Joined: Sun Mar 08, 2015 6:17 pm
Posts: 4
Hey,

So I ended up taking my low speed compression setup apart because it was seized up on my 2011 Van RC and this metal ring fell out in three pieces. I am assuming it isnt suppose to be like this haha. Any chance you have any manuals that show this low speed compression unit? Here is a photo of what I am referring to. it looks like the DHX has a propedal adjustment on the top of the resi opposed to a low speed compression.

http://www.pinkbike.com/photo/12017742/


Thanks!


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 Post subject: Re: Fox DHX 4.0 Rebuild
PostPosted: Wed Mar 18, 2015 3:36 am 
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big hucker
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Joined: Wed Jan 16, 2013 7:32 pm
Posts: 3086
Location: Dallas, TX
Damn. I think you found the root cause of the problem...

I just searched through everything I have and I can't find any diagrams newer than 2008. None for the Van RC. If I run across something I'll surely post it up.

It might be worth a call to Fox. They've helped me track down part numbers for pieces I couldn't find on a diagram.

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