JimsGX

Hi Guys,

I know we like to keep the posts as short as possible, but I need to give you some history in order to help me figure this one out. 91LS… I have one final vibration I’ve been trying to fix for two years now, and I need your help in figuring out what’s wrong here… The vibration is coming from the front half of the car and only happens between 25 and 30mph. It’s more pronounced when decelerating/coasting, but it’s there when accelerating as well, it’s just masked a bit during acceleration, plus the amount of time you stay in this mph range when accelerating is minimal... It does it both in gear or when I put the tranny in neutral and let the car coast down below 30mph. It started about 2 years / 12k miles ago. At first, I’d have to drive the car for 20~25miles before it would start vibrating, then eventually it started doing it all the time, right from the get go. It hasn’t gotten any worse over the last 12k miles. This is what perplexes me. You’d think it would get worse over time/miles as whatever was causing it would get more worn out, but it’s exactly the same as it was 2 years / 12k miles ago. You can feel it through the steering wheel, but you feel it through the car as well. Applying the brakes when it’s vibrating, or turning the wheel, doesn’t change the vibration. A couple of weeks before it started, I had the Y pipe replaced with an aftermarket Wagner pipe. I’ve tried temporarily stuffing some heavy duty foam padding above both sets of mufflers and taking it for test drives to see if it was an exhaust vibration, but it doesn’t make any difference. Here’s what I’ve changed on the car over the last two years since / after the problem started:

Front Strut Rod Bushings/Cushions (OEM)
Front Upper Control Arms & Ball Joints (Arnott)
Front & Rear Sway Bar Bushings (Daizen)
Front Lower Control Arm Bushings (OEM pressed in)
Engine and Transmission Mounts (3) (OEM)
Drive Shaft / Propeller Shaft (brand new OEM including center bearing and isolator pads)
New brakes all around, including new Rotors, Calipers & Pads
New Butterfly Support Bracket that supports the front exhaust Y pipe (OEM)
New Catalytic Converters (3, including the one built into the Y pipe) (all Wagner)
New 17” Lexus Rims and Michelin Primacy Tires (problem existed when the 15” stocks were on)
New Rear Differential (used w/13k miles on it)
New Rear Differential Bushings (3) (OEM)
New Rear Driveshafts (2) (OEM)
New Rear Carrier Arm Bushings (ADUS 505)
New Rear Strut Rods w/Bushings (OEM)
New Rear Upper Control Arms w/Ball Joints (OEM)
Full Tranny Flush

So what’s left to replace? Lower ball joints, inner and outer tie rod ends, shocks/struts, sway bar links and wheel bearings…

I do know that the adjustment locknut on the right inner tie rod is frozen and even heating it doesn’t free it up. The alignment was recently checked on a Hunter and it’s right in spec. The rack doesn’t leak, and I recently did a PS flush.

Occasionally, when turning the wheel to the right at speeds of 15~35mph, something feels like its catching / grabbing on the passenger side steering. Because of this, I’m going to replace both the inner and outer tie rod ends as well as the lower ball joints on both sides.

The car drives exceptionally well, as it should after replacing all this stuff. There are absolutely no suspension or wheel bearing noises and the shocks are solid. The car only has 88k miles on it and drives like a 2005 except for this one vibration. So what the heck is it???

And BTW, I've paid Lexus twice to diagnose this and my indy mechanic has looked at it half a dozen times. They can't figure it out...

Thanks for your help,
Jim

Garage7RP

iTrader: (1)

Reading from your list, have you checked the steering rack buchings?

JimsGX

No I haven't... To replace them, do you know if they need to slide over the end of the rack via the passenger side after removing the tie rod end, or are they split and can be installed with the tie rod ends still intact?

Thanks

skperformance

iTrader: (6)

I am pretty sure the rack bushing mentioned is a split circle to slide around it without removal.
I doubt it is the rack since it would be constant and effects steering feel not vibration.
Change the tie rods since they are rusted.
Then get a good alignment , also double check the strut rods again as they go bad all the time. Press them with a pry bar to make sure no cracks are present.

BLKonBLK98

rack bushings are split.

Garage7RP

iTrader: (1)

The steering rack bushings are split and can be replaced by removing the (4) 17mm nuts/bolts from the cross member. You can check them first is they are worn out. If they are still good, make sure those nuts/bolts are tight and the steering dampener is also tight.

JimsGX

Thanks...

I'm going to replace the inner and outer tie rods on both sides as well as the lower ball joints as long as I'm down there. I already have all the parts. I just did the strut rod cushions a month or two ago so that can't be it. The original ones I took out didn't look bad either. I'll fiddle around with the rack and order two new bushings for it. I think they're relatively inexpensive. I checked the rack bolts a while ago and they were all tight. Can someone tell me if they have a gap between the upper and lower halves of the brackets when the rack bolts are tight? Mine don't have a space there so they're clamped down as far as they can go, but that doesn't necessarily mean that they're snug to the rack now does it? The rack and pump are original. 18yrs/88k miles and no leaks... I replaced the steering damper about 10k miles ago. I forgot to put that on my original replacement list.

Any other ideas, please let me know.

Thanks!

Jim

masagsxr

How about your mounts? I know Garage7RP had just replaced both his motor mounts and tranny mount.

You can see from here how the bad the old ones were and his is a 93 vs your 91.

https://www.clublexus.com/forums/ls4...placement.html

JimsGX

All three mounts have been replaced...

Garage7RP

iTrader: (1)

The steering rack bushings and the "U" clamps should not have any space in between them.

BTW, have you checked for any unusual play in your front wheel bearings?

JimsGX

I checked the rack bushings tonight and they look to be in very good shape and the clamps don't have any space in between them. I took a 1/2" breaker bar to the four 17mm clamp bolts and they're tight as can be.

I checked the front bearings and I just had my indy mechanic check them. They don't have any side to side play in them at all.

I guess I'll go forward with the LBJ's and inner/outer tie rods this weekend. The right inner tie rod needs to be replaced anyways since the adjustment nut is frozen.

I remember seeing a single post some time ago about someone replacing lower ball joints and having it fix a front end vibration problem. Even though the ball joints weren't making any noise and didn't appear to have any play in them.

Thanks!

Amskeptic

Throwing guesses at the wall can be very expensive.

Ask yourself what the frequency of this vibration is:

Is it equal to vehicle speed?tire rotation?

Is it a higher frequency but related to vehicle speed, (driveshaft)?

Is it a harmonic that relates to engine rpms?

Probably the most classic sink-hole of vibration is the driveshaft. The first consideration is that it must be exactly parallel from transmission to differential. No fooling around. The second consideration is to look extremely carefully at your bolts on the coupling. Toyota offers heavy bolts that you use to finish-balance the driveshaft. A technician/home mechanic who is not aware that you must note/index the bolt positions might inadvertantly pile up two heavy bolts on one end of the driveshaft or imbalance the thing just by putting them back in the wrong position.

YMMV
Colin

JimsGX

Guesses are all I have since no one has been able to identify the root cause of the problem or point to a part and say "oh yeah, that bushing is gone, or that lower ball joint has play in it" Even the Lexus tech at my local dealer that's been working on these cars since 1990 doesn't know what it is. He keeps guessing. If you look at my laundry list of parts in the original post, you'll notice that I'm running out of things to replace and most all of the high cost items have been covered.

Driveshaft and couplings are new as stated in my original post. Lexus put the shaft in and did the final balancing, including putting the properly weighted bolts in and using the SST to check the angle. Replacing the shaft was my Lexus' dealers first recommendation to fix the problem. I had them do it as opposed to an indy mechanic just for the reasons that you stated. It made absolutely no difference in fixing the problem.

25~30 mph low frequency vibration. Same frequency as thunder. Not RPM related. As stated in my original post, does it at the same speed even with the transmission in neutral and coasting. The vibration hasn't changed in 12k miles. Hasn't gotten worse or better... If it were a wheel bearing or mechanical suspension part such as a ball joint, I'd expect it to get much worse over 12k miles, but it hasn't.

Thanks

JBrady

Torque converters can vibrate but since yours vibrates in neutral that doesnt seem likely.

How about an aerodynamic situation? A body panel or underbody panel or something actually vibrating at those air speeds? Much like a harmonic.

JimsGX

I thought about the possibility of a harmonic. I've checked the most obvious things like the front cowling and the plastic undercarriage engine splash / shield. I've tried running with the shield off and it didn't have an affect. I was thinking about covering up the slots in the front cowling and taking that for a drive.

The best way to describe the vibration is the WAP, WAP noise you get when you roll one of the rear windows down on the highway. It's about that same frequency and repetition. Not as annoying as that though.

One thing i know for sure is I'm not going to give up until a figure it out. I also have a webcam that I was thinking of hooking up to my laptop and positioning under the car then taking it for a drive. Sounds extreme but what the heck. I like a challenge.

Thanks