2004 GX470, clanking noise from rear when accelerating hard

[CNTAutomobilia]

Hey everyone,

I just bought a 2004 GX470 with 200k miles 2 days ago. It has a good deal of rust underneath, but aside from this it’s decent, especially considering I got it for less than half it’s value. The biggest issue is, upon hard acceleration, there’s a loud clanking sound from the rear. The previous owner stated that he thought it was the trans, but the trans shifts smoothly with no weird behavior. If I give it light or medium throttle it’s fine. Hard throttle and the sound is heard and felt.

what do you all think it is? Thank you

 

[Sgn2bapt]

My guess is the rear differential. If you want to sell it, let me know

 

[Toyoland66]

Check your u-joints for play. Make sure the driveshaft flange bolts are tight. With the car off and in park, e-brake off, have someone rock the car forward and back by pushing on the front or rear bumper and watch the rear pinion and driveshaft from the side, the pinion will jump around if you have a bad pinion bearing.

 

[Commander AJ]

The first thing I would do is drain the rear diff fluid and see what kind of metal shavings or chunks come out. It almost sounds like it has some broken teeth on the rear diff gears. If you got a great deal on it then it is for sure worth getting the rear end rebuilt and you get to pick your new gear ratios! Good luck amigo, let us know the outcome.

 

[CNTAutomobilia]

My guess is the rear differential. If you want to sell it, let me know

$5000 and it’s yours in its current condition

 

[CNTAutomobilia]

Thanks guys. I’ll start looking into these things

 

[thatcabledude]

Maybe broken (rusted through?) exhaust mounting bracket causing exhaust to sag and/or move and come into contact with the driveshaft when the engine is under load?

Look for shiney spots on driveshaft and exhaust.

 

[GXO]

That sounds like a ujoint or rear diff. Could be an ebrake shoe popping

 

[TahoeLX450]

Thanks guys. I’ll start looking into these things

I would think if you power up with the brake on it would stop after a couple of clunks if it were the rear end, U-joint or exhaust hitting something... From the sound of you video it seems to keep going like the transmission...or possibly the rear end. Yet, have you checked the motor mounts? If you have a broken motor mount (MM) the lift of the motor as it torques and lifts up could be binding the transmission in some way and causing the torque converter to make that ratcheting sound. What ever it is don't continue to cause this ratcheting sound as something is very wrong.

To check the MM open the hood or crawl under and inspect. But, keep in mind that you can't always see a broken mount because the frame and engine bolting brackets have separated from the rubber dampener in between them and it's hard to tell when stopped because it is sitting in the cradle as if fine. But they will separate when under acceleration. To check the MM have someone slightly give gas in gear and you watch to see if the motor raises up from one side. Usually the driver's side depending on which way the crank rotates. It will be very obvious if it jumps. Be very careful not to rev to hard as you could break the opposite side mount and then the engine is only held in place by the trans-mounts and not a good scenario as you could break all sorts of things that depend on the engine staying put. If my suspicion is correct you may already have broken both and the engine is jumping up and twisting and binding something under acceleration. I hope this is it because motor mounts are cheap and somewhat easy to replace with hand tools and a good jack.

Although, listening to it again (after I wrote the above) and if in fact coming from the rear and not the trans tunnel it may be a broken pinion gear or hopefully just a rear U-joint about ready to shear off. Again, I just listened again and you think its coming from the rear but check the MM wouldn't hurt..

 

[CNTAutomobilia]

Thanks for the ideas everyone. I was driving it yesterday and I came to a stop sign. Once I started driving from the stop sign, I Felt the rear wheels slow down despite my throttle, as if the parking brake was on... there was a groaning sound from the rear wheels. I assumed the rear diff locked up on me, so I pulled over and put the truck in park, thinking I’d have to find some way to get a ride from where I was...

I tried driving it again and I was able to get the rear wheels free rolling again. it didn’t bind again after that, but there was more chatter back there under normal acceleration. Almost like an exhaust rattle but obviously it’s not.

don’t know that this symptom means as a part of the puzzle now, but that happened yesterday.

 

[TahoeLX450]

Thanks for the ideas everyone. I was driving it yesterday and I came to a stop sign. Once I started driving from the stop sign, I Felt the rear wheels slow down despite my throttle, as if the parking brake was on... there was a groaning sound from the rear wheels. I assumed the rear diff locked up on me, so I pulled over and put the truck in park, thinking I’d have to find some way to get a ride from where I was...

I tried driving it again and I was able to get the rear wheels free rolling again. it didn’t bind again after that, but there was more chatter back there under normal acceleration. Almost like an exhaust rattle but obviously it’s not.

don’t know that this symptom means as a part of the puzzle now, but that happened yesterday.

I would recommend not driving it and getting it to a differential shop ASAP. Who knows, maybe the diff leaked dry. Seams like low mileage for a diff to go on these vehicles. Could be an axle bearing too. Either way driving it when what ever it is going bad may leave you stranded at best or breaking some thing else like a diff housing or an axle at worst. A broken axle could cause the wheel to come off...

See: Yours kind sounds like :45 You don't want to end up like 1:50 or 2:20

 

[CNTAutomobilia]

Yeah I bought it to sell because I got it for a good deal, so my goal is to fix it and sell it, so I’m not driving it until I get it to the mechanic. I’m going to bring it in this week. I’m going to tow it in. You recommend a diff shop vs. an all around mechanic?
PS. Here are some underbody pics. Maybe this can help.

 

[little_joe]

Good grief, looks as if a PO let that thing sit in salt water for a while. That rear driveshaft looks terrible - the u-joints are horribly corroded and appear to be dry, at a minimum I'd try greasing them and the slip yoke, or better yet just replace it all. Would love to see what the rear diff gear oil looks like when drained as well....

 

[CNTAutomobilia]

Good grief, looks as if a PO let that thing sit in salt water for a while. That rear driveshaft looks terrible - the u-joints are horribly corroded and appear to be dry, at a minimum I'd try greasing them and the slip yoke, or better yet just replace it all. Would love to see what the rear diff gear oil looks like when drained as well....

Any links to replacement driveshaft/slip yokes that are of good quality? Might need to replace the rear diff too I’m assuming

 

[Toyoland66]

OEM complete driveshafts aren’t too expensive especially if you order from UAE, maybe $300-$350. No idea if any aftermarket ones are good. Start by greasing them and see if that helps (3 zerks per shaft/ each u joint and the slip).

you have a leak from the t-case actuator I know I’ve seen threads here on how to fix that, in the meantime you should check the oil level to make sure it isn’t low.

 

[GXO]

If you can't check gear oil levels, grease zerks, etc I would be highly suspect of your ability to flip this vehicle for profit. Time to learn some mechanical fun! The actuator seal is actually about a 30 minute repair and there is a great post here on how to do it.

 

[Sgn2bapt]

@Vlad best advice so far.

 

[CNTAutomobilia]

If you can't check gear oil levels, grease zerks, etc I would be highly suspect of your ability to flip this vehicle for profit. Time to learn some mechanical fun! The actuator seal is actually about a 30 minute repair and there is a great post here on how to do it.

Not sure why you have to suspect my ability to do anything. I’ve sold quite a few cars for profit. I’ve also completely replaced the control arms, steering rack, wheel bearing, rotors, pads, alternator, and sway bar on a 2006 Toyota Sienna AWD, Parked on the street in the middle of a NYC winter before lol.

However, I’ve bought this Lexus for so cheap that I can afford to have my mechanic look it over, and do whatever work is needed if I wanted to, and I can still make a profit.

but I appreciate the guidance in what to look for and what to grease. I’ll take a look in those areas.

 

[TahoeLX450]

Yeah I bought it to sell because I got it for a good deal, so my goal is to fix it and sell it, so I’m not driving it until I get it to the mechanic. I’m going to bring it in this week. I’m going to tow it in. You recommend a diff shop vs. an all around mechanic?
PS. Here are some underbody pics. Maybe this can help.

View attachment 2390768

View attachment 2390769

View attachment 2390770

View attachment 2390771

Wow, not cared for... Some shops can work on diffs and some don't. Just call around. Question: If the undercarriage is that rusty is the body as bad? Interesting to see a new shock in the rear.

 

[CNTAutomobilia]

Wow, not cared for... Some shops can work on diffs and some don't. Just call around. Question: If the undercarriage is that rusty is the body as bad? Interesting to see a new shock in the rear.

Body is great aside from some fading clear coat, which I will address. Not a spot of rust anywhere on the body. Previous owner replaced the shocks, timing belt, water pump, and any other items his mechanic told him to in the last couple years. I guess his mechanic didn’t recommend any work on the frame rust or differential though smh.