Questions about front diff clunk, lockers, and lifts

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M

mokrunka

Joined
Jan 15, 2024
Threads
13
Messages
146
Location
LA
Hi folks. 02 100 (215k miles) series owner here. I've owned it for 2.5 years, and have been slowly going through it getting it baselined, and fixing things up. I've done a ton of work in this time. The list is below to give an idea of where I am. But now, as I am on a quest for some more off-road capability, I need some advice, because I've never build a rig for offroading and am fairly new to this world. The truck is on 33" KO3s.

I've chased the 'clunk' when shifting into D or R or vice versa endlessly. It's still there. I crawled under there and had someone shift it a bit with their foot on the brake, and I can see the front prop shaft turning, and this seems to be the source of the clunk, which I assume is either backlash in the geartrain or (maybe) u-joints. This has me thinking that maybe my front diff is on its last legs, and it's time to replace it. Since I'd have the opportunity, I'm considering adding e-lockers to the diff. Then of course the question is should I also do the rear diff? This is of course a lot of money, so I'm wondering if they HAVE to be done at the same time or not? I've read many forum posts and it seems folks suggest doing the rear at the same time so that the front diff isn't pulling the truck, and wearing it harder. So that's question 1 - should I just full send and replace both front and rear diffs with lockers? Obviously I'd get new ring and pinion in the front - do folks normally replace the ring and pinion in the rear when locking it as well?

Next question is the topic of lifts. I've never had a lifted vehicle. I do not yet have armor like rock sliders or under armor yet. I've found when I'm wheeling, I'm concerned about being able to crawl over rocks without breaking something under the truck. Is my money better spent on armor at this point? Should I get a lift of some kind? What I've read here seems to indicate that a body lift isn't doing much other than protecting the body, which I'm not OVERLY worried about (of course I'd like not to bang it up too bad), but mainly I'm concerned with not getting stuck or stranded with broken mechanicals.

Truck is not a daily driver. And I'm not trying to do the Rubicon or anything, but it'd be nice to be able to handle some of the harder stuff with rocks and such without being as concerned about breaking something.

List of things I've done (all parts OEM - this is just the relevant suspension stuff, not all the usual baselining in the engine bay):
  • front UCA
  • front shocks
  • rear upper and lower CAs
  • front outer tie rods
  • CV joints
  • front diff bushings
  • hub flanges
  • greased driveshafts
  • changed all diff and t-case fluids
  • front and rear sway bar end links
  • new front wheel bearings
 
You can definitely experience some clunking out of the diff if there is excessive backlash. You also didn't list lower control arm bushings, which is another likely area of movement. Non-OEM axles and flanges are another common area after "replacement." Also engine and transmission mounts. Body-on-frame vehicles with automatic transmissions will always have some clunk.

If you are keeping the same gear ratio, you can just do the front and leave the rear. Only need to do the rear at the same time if you change gearing. A rear locker is much more useful than a front, but it's not going to hurt anything.

Full skids are the most useful protection you can buy IME.
 
Thanks for the feedback. Yes, I’m planning to get the ASFIR skid plates. I have not yet tackled the LCAs, but they’re on the list. All the parts I’ve listed and put on elsewhere are OEM, so no aftermarket axles or hubs or anything like that.

I wouldn’t be so concerned about the clunking if I was sure it wouldn’t result in a broken front differential leaving me stranded, but the amount of clunking that I’m having is not what I’d consider normal.
 
I wouldn't worry about the clunk too much. They all seem to do it, and I don't think its a concern about something breaking. I think you are on the right track that it is front-drive related. Probably minor amounts of slack/loading in the moving/wear components of that part of the drivetrain (front driveshaft u-joints and splines, r&p, CV axles, and drive flanges) plus anything that holds those components in position (front diff bushings).

Going part-time/2wd eliminated my clunk completely, so that def skews my perception. No load on any of that now when in 2wd and zero clunk.
 
It kind of feels like the very last item on the usual suspects list for a clunk would be gear lash. My experience was that it was all additive—no single fix got rid of the clunk, had to be all of it. I'd bet if you removed the front driveshaft and took it for a drive, the clunk would be gone, and it kind of sounds like you're already on that thread anyway after having a look underneath. Front drive shafts aren't the most insanely expensive thing from Toyota, and can also be refreshed with new ujoints (or have a local driveshaft shop do it). Check the shaft itself while it's off the truck, there should be little to no rotational play in it.

If you want to be very sure on the ring gear, just take the front wheels off the ground, remove the front driveshaft, and check the amount of play in that front diff by just turning it. Should be quite tight, where any input almost immediately begins turning the wheels. Kind of a PITA, but also free to check. And if that really is the issue, you'll know where to sink cash instead of having an armored lawn ornament.

Or do the 2WD conversion hah. Aisin hubs look amazing!
 
Agree on the LCA bushings as "really hope this is the last thing" on the front end suspension redo. There's probably a good bit of movement there after 250k or 25yrs. U-joints, if they've never been done, too. Chasing slack out. Mine still has some clunk but about every time I get under there and replace something it reduces 5-10%. By the time I get all of it replaced, it'll probably be time to start over. Haven't had to rebuild a front diff yet (knock wood) in spite of 5-6yrs worth of several times a year taking it out to beat on it, too, so there's an anecdotal point.

I tell everyone my first armor recommendation is sliders. The underside of a LC is not terribly exposed and most of the stuff under there is relatively tough or has some basic protection already, but your rocker panels and lower doors ARE pretty exposed and not anywhere near as tough. The very FIRST time you have to get a rocker panel reformed or replace a door and get stuff painted... you'll spend more than that. Best is both, but if you want to prioritize, the sliders are first IMO.
 
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