huffju

So not to hijack someone else's thread, I will post up my issue.
I'm experiencing odd and discomforting issue with my 97 LS400. After weeks of searching, I've yet to find a resolution.

Symptoms and notables:

-NO CEL LIGHT
-Car starts up with no effort every time regardless of temp.
-Motor appears very static upon start up (do not suspect motor mounts)
-Warm-up RPM is 1300-1400 rpm
-Operating RPM in PARK 650'ish
-When DRIVE is selected, a 300-400 rpm increase is seen, followed by a "THUMP", and then settles at 400 rpm while under load. * When the A/C is ON, the motor returns and always settles when coming to a stop @ 650 rpm*
-REVERSE illustrates the identical symptoms without the thump and increase in RPM
-When removing the gear selector from DRIVE, a "THUMP is again heard

The car has been serviced at LEXUS most of its life with only one owner. Documentation shows a good owner from 0-167k miles, but not further documentation through 215k at which point I purchased the car.

Motor and Trans mount was replaced around 160k, IIRC without looking back at the records. The Trans was said to have been serviced just a month prior to my purchase....which actually leads me to be slightly suspicious. I've since had a drain/fill a week ago even though the fluid appeared/smelled within acceptable condition. The car appears as though it were a 50-75k mile car from interior-exterior-engine. So it does not appear that it has been neglected in any stretch of the imagination.

My next idea was to just purchase new solenoids and replace them and see if it resolved the issue.

I have searched and searched the web and lexus specialty sites, but to no avail. Does anyone have a clue what is going on here???

Thank you,
Justin

PureDrifter

iTrader: (10)

the trans sounds fine. the trans mount and the guibo joint in the driveshaft sounds beat up though.

replace the trans mount, then if needed the guibo bushing in the driveshaft. given that the trans mount is a giant piece of squishy rubber i wouldnt be surprised if you're due for one. one of those compromises for comfort/nvh vs. longevity that lexus made.

huffju

Thank you! The local Lexus dealership has a mount in stock and I will check on the other unit as well. After I install them, I will report back.... I just hate it when others have an issue and do not report the resolution. Kinda' defeats the purpose! LOL

huffju

So as it turns out...the trans mount is like new, which isn't far fetched considering it was replaced 50 k miles ago with the engine mounts. The driveshaft bushings could use replacement eventually, but ok for now. However, the big clunk or thump when selecting a gear is coming from the rear differential mount / bushing.... We placed the car in the air and went through the gears....the rear differential was of course torquing up and down with .25-.35 inch of play. Problem solved with the sound.

If I understand correctly, the LS is suppose to operate in the rpm range described but without the harsh shift. Please correct me if this info is incorrect.

SpencerT

My transmission does this exact same thing so I would be interested in info or a fix for this problem as well.

huffju

My suggestion is to simply replicate what I posted above to eliminate it as an option for you.

As far as the fix, it's about 125-150 dollar bushing replacement. I ordered mine today and will pick it up Saturday at Lexus. Very straightforward replacement ....

SpencerT

any tutorials for that diy?
does it involve dropping the differential?

huffju

I will build one from my install on Saturday or Sunday. From what I remember from my MKIV Supra (double ear mount vs single -LS400), you will be dropping the rear, but not so much that it is completely "removed" from the car. But again, I will build a simply DIY guide with photos for future reference to aid others with this very common issue.

dashan

Could you please post part number here? Some members would be very interested in this piece of information.

SpencerT

You most deffinatly should do that

PureDrifter

iTrader: (10)

how did you check the transmission bushing? the only way to see if its broken or not is to jack up the rear of the trans ~1/2-3/4" as under load the bushings is compressed and looks fine.

huffju

We place the car in the air, started the car, selected, Drive, Reverse, and Park multiple times to replicate what I would see and hear while the car was on the ground/underload. The bushing has approximately >0.25 in of slop, thus when we selected drive and place the car "underload....you can watch the rear diff torque semi-violently, slapping the diff up and down....

I suppose I could attempt to actually video it prior to the install in the morning. I had intended upon making the repair today, but after working 12hrs last night, getting groceries and running by Lexus to pick up the parts, I was done for the day. When I get off work in the morning, I will start the repair and attempt to remember to post everything up by mid afternoon to share the conclusion. If for whatever reason this does not completely eliminate the "thud," which I believe it will in my case, then I will mover up the driveline and replace the "flex bushings" on the driveshaft. They doe show wear, but not so much that I believe it to be the main contributing factor in my personal case.

The bottom line is that my eyes and my fellow "car guy" believe the rear diff is the cause....guess only time will tell

Part #? Sure, not a problem....In fact...HAHAHA..I will make sure you don't waste an extra $20+ like I did!

More in the afternoon guys...And thank you for everyones input thus far. It's great to know this community and resource exist for car nuts like ourselves

huffju

I'm Sorry PD....I misread your post. To answer your question, we took pressure off of the bushing, visually and physically inspected it. I've replace enough bushings and driveline components to reallize that sometimes you can get fooled until you actually remove the part and find the surprise. But in this case, I wasn't so lucky....I may still replace it while I have the time, but not before I test out the rear diff bushing in order to isolate the culprit.....

Sorry, hope that answered your question.

huffju

Ok guys, sorry I'm just able to get back on here, but here is the update.

The rear diff bushing was a sucess in that it removed the "thud" resulting from the semi-agressive gear selection. However, as suspected, I still have the infamous "lurching" or lunging 50-60% of the time when Drive and Reverse is selected.

I'm going to check the kickdown cable for adjustment next....If in fact there is no change, I will move to the TPS. According to a Lexus "master mechanic", the point within the TPS may become worn and result in these symptoms without kicking out a CEL. Unfortunately, a new TPS is most likely warranted anyway, due to the mileage and lack of documentation for this particular part. So I'm sure 215k miles is good enough for a retirement, dont ya' think?

If neither of the above resolve the problem, I'm open to more suggestions....But I will let you know over the next week as this unfolds. Also, I have not forgotten about the write up....