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Removing the Baja transmission & adding differential fluid.

February 3, 2009 by  
Filed under Tutorials

From the factory, the HPI Baja 5b RTR and 5T diff is usually under filled or dry. Checking and filling the diff should be done before you run your HPI Baja for the first time. Please take the time to do this if you don’t, your diff will wear out prematurely. The task isn’t hard but there are several steps. Make sure you have plenty of time and space to do this maintenance task. It will help to have a few small boxes or containers handy to place your parts in. It will also help to have a rag handy. Take your time, look at the photos, and read your owners manual. This is a great time to get to know your HPI Baja 5b. If have been running your rig this is a great time to clean everything and inspect for damage and to replace any worn out parts. Parts needed:
  • Diff lube (Supplied in the fluid bag of your new Baja)
  • Diff gasket (Supplied in the fluid bag of your new Baja)
Optional Items: Tools: Time: 2-5 Hours depending on your shill level. Skill level: Medium Step 1: Preform Brake Maintenance Remove the HPI Baja roll bar by taking off the 4 clips, one on each corner of the cage. You will need to remove both shocks and the shock tower brace using a 3mm wrench. HPI Baja - Removing the Diff HPI Baja - Removing the Diff If you have a stinger on your stock exhaust remove the support bracket then Remove your exhaust can. There are two screws 4mm on the front. If your looking for a little better performance, don’t re-install the stinger pipe onto the exhaust can during re-assembly. The can should come off with a little finger pressure. Take note of the exhaust gasket. If it is riped or torn, replace it. HPI Baja - Removing the Diff HPI Baja - Removing the Diff Remove the rear bumper cage. 2- 3mm screws on the top plate and 2 on the bottom. With a little wiggling it will slide off. Watch out for the nuts that are used on the bottom screws they will most-likely fall out. HPI Baja - Removing the Diff HPI Baja - Removing the Diff HPI Baja - Removing the Diff Remove the screws from the rear top ball ends using a 3mm hex wrench. HPI Baja - Removing the Diff Slide out the 2 hinge pins holding the upper A-Arms. They should easily slide out. If needed you can use a pair of pliers to help. If you need pliers, check to see if the pins are bent. If so, replace them. HPI Baja - Removing the Diff HPI Baja - Removing the Diff Remove the remaining 2 screws in the top plate. Watch for the nuts on the bottom and the copper colored brake shaft bushing, they will most-likely fall out. HPI Baja - Removing the Diff HPI Baja - Removing the Diff Remove 2 screws from the each shock tower again watching for the nuts. The towers will fall right off. HPI Baja - Removing the Diff HPI Baja - Removing the Diff HPI Baja - Removing the Diff On the bottom of the chassis remove the 4 screws that hold the gear box to the chassis. HPI Baja - Removing the Diff Slide the inner boots off the out drives. HPI Baja - Removing the Diff Now lift the gear box out. HPI Baja - Removing the Diff HPI Baja - Removing the Diff Congratulations, you now have the easter egg in your hand. Go enjoy your favorite beverage. HPI Baja - Removing the Diff Using a 2.5mm hex wrench remove the cross pin that holds the brake hub and slide the hub off the shaft. HPI Baja - Removing the Diff With your 2.5mm wrench remove the 5 self taping screws from the diff case. HPI Baja - Removing the Diff Gently slide the 2 halves of the case apart. Dont worry, nothing will crawl out and byte you. HPI Baja - Removing the Diff HPI Baja - Removing the Diff HPI Baja - Removing the Diff HPI Baja - Removing the Diff Do keep an eye out for the 2 cross braces that are on the inside. They slide in on the bottom of the case and have those pesky little nuts in them. Keep an eye out during assembly to see that the nuts are there and in place before you seal the case back up. HPI Baja - Removing the Diff Remove the 4 screws that hold the gear on. Again, watch for the nuts. HPI Baja - Removing the Diff Remove the gear from the case being careful you only remove the gear and not the top of the case. Try not to separate the case at this point. It will help keep things clean if make sure to hold the diff upright as shown in the photo. HPI Baja - Removing the Diff Hold the case upright and remove the top cover. HPI Baja - Removing the Diff As you are removing the cover, there is a diff gear that may be stuck to the case or it may be laying on the top of the 2nd case half. Go ahead and remove it so it doesn’t fall out or get lost. During assembly this gear will set into the top half of the diff case and needs to be set onto the cross pin properly or the case wont properly close. HPI Baja - Removing the Diff Remove the rubber gasket that seals the two case halves. Its recommended to replace this gasket each time you take the diff apart. There is a new one included in the spare parts bag of your new HPI Baja. During reassembly, make sure you have the gasket properly seated in the groove as not to pinch it. HPI Baja - Removing the Diff At this point you can inspect and replace any worn parts you find inside the diff. We are not going to go into rebuilding the inside of the diff at this time. Look for another tutorial sometime in the near future. Guess what, Its DRY! Not a drop of viable lube in this bad boy. Fill the diff with the supplied diff lube or do some research and decide if you want to go with a different weight. This is entirely up to you. There are many opinions on diff fluid weight and how much to use. We chose to use Mugen 7K weight and to fill the diff up to just above the cross pins. As you are filling the diff make sure you rotate the gears to allow the fluid to go down inside the case. If you just dribble some in and close the case you will not have gotten enough in there. Let it sit for a few minutes then check it again. Repeat this process until you are sure the fluid has settled in and there is enough. HPI Baja - Removing the Diff We chose to replace all the bearings at this time before we reassembled the diff. HPI Baja - Removing the Diff HPI Baja - Removing the Diff HPI Baja - Removing the Diff To reassemble your HPI Baja 5b, follow the tutorial backwards referring to the photos and descriptions to help guide you. During the making of this guide we chose to use a Stainless Steel screw kit to replace the factory screws. Stainless Steel doesn’t rust and offers much better protection against the elements. I also have to say they look great. We also chose to replace the bearings at the time of this guide. In our shop we use only Blue Locktite jell stick. Its a lot less messy and can accurately be applied to the threads more so then liquid. Our biggest reason is that it doesn’t separate so there is no need to shake it up before every use. If you’ve find this How to guide or tutorial helpful. You can show you support by visiting our sponsor TeamFastEddy.com.

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