Nasty grinding in 4wd after ECGS bushing install

[Blobbins]

Background: 2001 4Runner SR5, 96-98 LTD style transfer case (rear locker, locked center)

I was having an intermittent 'rumble strip' vibration that matched what is described here:

https://www.tacomaworld.com/threads...differential-bearing-vibration-thread.152173/

I ordered the ECGS bushing to replace the drivers side differential needle bearing, and installed it. The bushing stuck out .040 past the carrier, seen here:

After buttoning everything up, I took it for a test drive. When I press the 4HI button on the transfer case lever, I can hear a 'clack' and the 4wd light on the dash goes on as normal.

However, a horrible grinding noise (with corresponding vibration in floorboards) happens when I begin to drive in 4HI. Grinding is proportional to wheel speed, with maybe 4 'grinds' per wheel rotation. No noise in 2HI or when stopped. It sounds like gears or splines not matching up and grinding against each other.

It could be unrelated to the bushing install, but it's never happened before. Truck had been sitting a couple months before install. The only thing I did was remove a cv, swap needle bearing for bushing, replace axle seal, reinsert cv, and top off diff oil.

How can I go about troubleshooting this? Is this more likely to be in the transfer case, diff, or maybe the ADD system?

 

[MStudt]

Did you read the information at the bottom off the page here? It talks about the exact noise you're hearing, and tells you the solution.

Here's the typed information, and there's a video or two.

DESCRIPTION

TECH NOTE: The T7.5 bushing is longer than the stock needle bearing. There is room for the bushing to install flush without hitting the spider gear, however some of the toyota carriers are not bored straight through and there is a ridge on the inside. The ridge will stop the bushing from seating flush. Installed height is between .030-.065 off of the carrier bore as acceptable. The bushing can be driven past the ridge of you hit it hard enough but it will damage the bushing and cause the CV shaft not install properly. Drive bushing in to carrier with even firm blows once you feel it stop verify height is between .030 -.065

 

[Blobbins]

Did you read the information at the bottom off the page here? It talks about the exact noise you're hearing, and tells you the solution.

By noise do you mean the rhythmic vibration that happens in 2wd and goes away in 4wd? Because that has been fixed by the bushing. The problem is that now, something is binding / grinding when I try to engage 4wd.

I drove the bushing in until it stuck out .040, which falls in the .030 -.065 range specified by ECGS, and I had no trouble reinserting the CV.

 

[MStudt]

By noise do you mean the rhythmic vibration that happens in 2wd and goes away in 4wd? Because that has been fixed by the bushing. The problem is that now, something is binding / grinding when I try to engage 4wd.

I drove the bushing in until it stuck out .040, which falls in the .030 -.065 range specified by ECGS, and I had no trouble reinserting the CV.

If you continue reading it does talk about the grinding noise you're hearing. You inserted the bushing as far as they said it "might" go in, but not how far it "should" go in. They sell a tool to seat the bushing the rest of the way, and that it what you need to do. Having it sitting out .40 of an inch is what's causing the grinding noise you're hearing, and they even say it on their site.

 

[Blobbins]

If you continue reading it does talk about the grinding noise you're hearing. You inserted the bushing as far as they said it "might" go in, but not how far it "should" go in. They sell a tool to seat the bushing the rest of the way, and that it what you need to do. Having it sitting out .40 of an inch is what's causing the grinding noise you're hearing, and they even say it on their site.

Sorry if I'm being thick, but where on the site does it mention this noise? I thought I read all the information on this install. The installation tool ECGS sells looks like the race driver I used.

The sound is a gravelly *crunkcrunkcrunkcrunk* noise, with associated impact felt through the floorboards. If .040 proud is within their acceptable range, I'd be a little surprised that it would cause this, unless it's causing one of the gears in the diff to be out of alignment or something.

 

[Blobbins]

Current plan is to borescope the diff while turning the driveshaft and see if I can suss out any damage to the gears.

If I'm not getting any noise in 2HI, I should be able to rule out damage to the spider gears and side gears right? Because they are spinning against each other any time the wheels are moving, but the ring/pinion only move when turning, and only move under load in 4wd. Do I have this right?

 

[Burke239]

Sorry to bring up an old post but did you figure out what was causing the noise and vibration?