Offroad Trailblazers and Envoys

FRONT DIFF SWAP

G80, GU6, GT4, GT5, WTF? This section is for gearing and driveline stuff.

by larryk » Mon Jun 27, 2016 8:44 pm

Guys, since I found out a lot of good pointers about swapping out my trans..AFTER I swapped it...figured I'd hit up you guys for the best way to swap the diff before I dig into it. I'm good with pretty much everything up to pulling the axles, disconnect, and intermediate shaft. Not sure on the best way to yank the actual diff out for my new one. Shop manual says to pull the pan, but I've heard (I recall I think) that that isn't needed.

Bring it on gentlemen :)
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by KingBird » Mon Jun 27, 2016 9:59 pm

I found that trying to drop the pan was useless.

I've done it two different ways. While trying to get it out by dropping the pan, I ended up removing all of the bolts and then split it and pulled it out in three pieces, the outer half, the diff and carrier, then the inner half. I put it back in the same way. I don't recommend this method.

The next try, I took the motor mounts loose and lifted the engine, then I trimmed part of the steel around the engine cradle to get the old one out and the new one in. I don't recommend this method.

If it happens again, and it may because I'm looking at an LSD for the front, I plan on pulling the air conditioning compressor, water neck, and alternator, then I'll just come straight out of the top.
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by Aries » Mon Jun 27, 2016 10:35 pm

Image
fishsticks wrote:Today was disassembly day.

Since most reports I could find of front diff removal were sketchy at best, I had to come up with my own plan of attack. I was set on not dropping the oil pan. My first plan was to jack the engine up as some have talked about and try to pull the front diff out from the rear of the motor. I ended up changing plans midway through as I just couldn't get the clearance to get it out that way. When all was said and done I removed the diff from the top of the engine bay.

Here's a roughly reorganized step by step for someone who wants to do this.

1. Jack front of truck up and support by the frame with jackstands placed approximately at the seam of the fenders/doors.
2. Remove front wheels.
3. Drain front diff fluid.
4. Drain cooling system.
5. Disconnect both outer tie rods from hub assemblies.
6. Disconnect ABS and brake lines from holddowns.
7. Disconnect upper control arms from upper balljoints. Allow hub assemblies to hang on lower ball joints. Make sure you aren't stressing ABS or brake lines.
8. Pop axle tripod joints out of diff and splined disconnect. (Letting the hubs hang first puts a little outward pressure on the CVs and makes this SO EASY).
9. Remove splined disconnect.
10. Remove intermediate shaft. I bought a slide hammer for this purpose and expected a fight. I didn't need it. I screwed one of the bolts that holds the PCM into the hole in the shaft and pulled. The shaft came right out. My inner seal was worn and leaking. The new seal had a bit more grab to it, and I needed the slide hammer to get it back out.
11. Disconnect the front driveshaft from the front differential yoke. Tie up and out of the way.
12. Remove driver side strut assembly. (Makes a lot of room to work.) The second time I didn't unbolt the assembly front the LCA. I just unbolted the two top nuts and pivoted it outwards as needed.
13. Unbolt radiator shroud support brackets.
14. Remove accessory belt.
15. Loosen PCM bolts.
16. Remove alternator and engine lift bracket. Also remove bolt from wiring harness tiedown nearby.
17. Disconnect battery and remove battery and tray.
18. Loosen top nut of passenger side motor mount. Remove top nut of driver's side motor mount.
19. Place jack and block of wood under oil pan. Jack up motor until driver side mount is free.
20. Unbolt driver side motor mount bracket. These are the 3 large bolts on the outside of the frame. Remove mount and bracket.
21. Use jack to move motor up and down to get at hard to reach bolts for next steps.
22. Remove driver's side coolant hose.
23. Remove idler pulley.
24. Remove thermostat.
25. Disconnect wiring plugs (2) from AC compressor.
26. Unbolt AC compressor. Pull up to top of engine through hole you've made. Leave lines connected (they'll flex).
27. Unbolt differential from oil pan. (2 bolts in front, 1 on bottom, 1 in rear near driveshaft yoke).
28. Lightly pry differential away from oil pan.
29. Pull differential up through top of engine bay.
30. Drink a beer, you deserve it.


Aside from that, I got to look over some original parts on my truck while they are off. Everything looks/sounds/spins surprisingly well for a 100K mile truck with a history of offroading.

I got some initial measurements off the front diff and then split the case. Turns out my right side carrier bearing race had some scuffing on it. I didn't get bearings when I ordered everything but the local Oreilly's had them in stock. Other bearings looked OK.

Not much in the way of pics today. Tomorrow I'll try to take some pics of the innards when I'm assembling.
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by larryk » Tue Jun 28, 2016 11:36 am

Good deal! So, you guys that have tried......why is dropping the pan out? I mean Id rather not....but what makes it more of a PITA than the jack the engine up/AC/Alternator method?
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by KingBird » Tue Jun 28, 2016 12:06 pm

The steering rack and the frame the goes across right below the oil pan. The pan only drops a couple inches below the studs that hold it on.
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by larryk » Tue Jun 28, 2016 5:25 pm

I'm going to swap in an SS rack and new lines when I do the diff...so that's not an issue. How about that crossmember....does it unbolt like the one behind the rack? I didn't look at it yet...but if I'm pulling the rack anyhow..?
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by KingBird » Tue Jun 28, 2016 11:02 pm

I'm not too sure.

This may be a dumb question, but why the SS rack? What are the pros and cons?
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by larryk » Wed Jun 29, 2016 6:37 am

KingBird wrote:I'm not too sure.

This may be a dumb question, but why the SS rack? What are the pros and cons?


It has a faster ratio. I have an EXT, and it has a faster ratio than the short wb....the ss is even quicker. Not as if the wiener dog, with the lift, is a sports car, but literally every fluid line on this truck has corroded, and I need to change then them before they rupture. As long as I'm changing it, I'm going to upgrade :)
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by KingBird » Wed Jun 29, 2016 10:27 am

Ah, good to know, I'll be on the lookout for an SS to jerk parts from.

You'll have to pardon my ignorance as I'm from West Texas, we have no clue what this "corrosion" is that you speak of. :lol:
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by navigator » Wed Jun 29, 2016 2:18 pm

I took mine out the top, followed Fish sticks method. If you are a.ready replacing a bunch of the front end components, it MIT make sense to come out the bottom like you said.
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by larryk » Wed Jun 29, 2016 3:24 pm

Rub it in why dont you....

But at least Im from the Midwest, and I dont know what rattlesnakes, and those drought things followed by biblical flooding is all about either :)
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by larryk » Tue Oct 25, 2016 10:10 am

Just to close out this thread.... I pulled the oil pan to drop the diff.....worked extremely well. Even if you arent replacing the rack, its only two bolts to drop it (along with diconnecting one bolt from the steering column). The crossmember that runs under the rack unbolts rather easily, but the two back 21mm Bolts are used to align the truck....so DO NOT loosen the front bolt (there are three, two in the back you have to take out, and one in the front you dont touch) unless you are good with getting an alignment after. Seriously, I didnt have to touch the coolant or even diconnect the battery. Granted, I had to change oil that still had 50% left, but oh well....
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by Anthony Hernandez » Tue Oct 25, 2016 12:06 pm

I pulled the ac, the alternator, and the pulley off, 'along with the fan and shroud, it was more than enough room. That sounds a bit more work, but either way as long as it gets done I suppose
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by larryk » Tue Oct 25, 2016 8:44 pm

True.... I think we can all agree that this is one horsecrap design....on many levels. I think about the only thing you can say, engineering wise, that makes sense, is you can drop the engine lower in the chassis for a better center of gravity and lower hoodline. Great concepts for a sports car, damn stupid ones for a truck.
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