Losiracer2

I've had this problem for awhile on my 97' where only when cold, the car would shudder when coming to a stop, almost as if the car was about to stall but then bumps the idle speed up and is normal.

I didn't have a CEL for the longest time, but PO770 came up recently, shift solenoid. My car currently has 274k on it, but I know that the previous owner said he already replaced that shift solenoid before.

What should I try to do first? I know its rather expensive, so I'd prefer not to buy another one for $300.

dicer

If they still used dashpots on that year that could be the problem. And since its very difficult to know what your experiencing all that we here can do it guess. So just because I say its a this or that it doesn't mean it is. One other thing it could be, if it feels like the car is dragging the engine down when coming to a stop is a problem with the torque converter or torque converter clutch, or the valveing for the clutch or solenoid. A shift solenoid should not do anything to drag the engine rpms down when coming to a stop. Unless it was trying to go into reverse or something. If 2 range clutch packs where trying to apply at the same time that would be stopping the car not the engine. So transmission related drag the engine down stuff is torque converter problems.

Banshee365

What happens if you manually downshift when coming to a stop when cold?

Losiracer2

I haven't tried that yet. Mainly because I try to be as easy on the engine when its warming up, so no abrupt RPM blips or acceleration until its past the tick mark just below the middle on the temp gauge.

all the gears work, if i were to manually command each gear they go into gear but its just the drag or slow down of the engine is what concerns me, as it seems its pretty violent when that happens. The entire car shakes and i'm sure its not good for the motor mounts either.

I think what i'll do is a drain and refill on the tranny with Toyota T4 fluid. Its been about 30k since the previous owner purchased the car (I was able to find out through searching his username on ClubLexus, KOZY, and found out he bought it somewhere around Oct 2014 w/ 244k and mentioned a few things that had been done to it but I know a tranny drain and fill wasn't one of them.)

Losiracer2

So I wanted to update anyone who's experiencing this same issue. I did the drain and refill procedure twice without any success, the code P0770 still popped up about a week later.

I talked to a previous Lexus tech who still owns an LS400 and he said that the transmission filter on these LS400s gets clogged rather easily and should be done every 20k miles or so to keep the transmission shifting nicely and in good running shape.

So since it was only $24 for a new filter and gasket, I opted to drain the fluid again and replace this filter. Sure enough, my filter, after supposedly having the shift solenoid replaced 30k miles ago, was dirty as hell. I'm not sure if they actually replaced the filter at that point or not though.

Here are some before and after pictures of the filter. The shift quality when cold is a lot better now and I'm not experiencing any shuddering. The difference was almost immediate, I'd say within 10 miles the shuddering was very light and now doesn't exist anymore, so the filter does play a big role in making that condition present or not exist at all.

dicer

In a good transmission there is pretty much nothing to clog the filter, so what are those little particles in the one photo of the screen? That is not a good sign.

RA40

iTrader: (6)

Glad you cleaned the filter. Looks a bit like road grit that may have been sucked in through the ATF dipstick. What did it feel like?

Losiracer2

A transmission has moving parts and will thus create wear over time. Why do you think there are 4 magnets stuck to the bottom of the pan? btw, my magnets were also caked in a metal like sludge. Not a huge amount, but enough to cover the surface of each magnet. My tranny has 274k on it so some wear is to be expected after all those miles.

I had done 2 drain/fills before, so i got the majority of the gunky old fluid out. So this third one had pretty much red fluid with a very slight amount of impurities. The bottom of the pan was sludgy for sure, just a slight trace amount that coated it. I cleaned it off with brake cleaner and wiped it dry before installing the new gasket around the perimeter of the flange. For some reason, I only had 3 magnets not 4, not sure if the previous people forgot to put the 4th one back or not.

Car is getting slightly better, I've only driven it about 20 miles since the new filter so some very slight shudder (only when very cold) is there but i'm guessing it'll work itself away after about 500 miles or so when the fluid has a chance to circulate through the solenoid.

dicer

I've opened recently a Subaru transmission with close to 300k miles and there is nothing in the screen even with not so nice fluid. Yes there is always some wear material but not like that. I've been fooling with automatic transmissions since about 1967. I've seen friction material and metal in a screen but not sure what that is, it looks gritty. If its bronze you have a problem.

Losiracer2

I'm hoping the grit is nothing bad. I originally was going to install a genuine Lexus OE filter, but the guy I bought the Lexus one from Craigslist sold me one for a 98-00 model for 15 bucks NIB saying he found it in the back of his 96...now I know why they didn't use it since it won't fit my 97, It came with a Fel-Pro gasket....also for a 98+ LS400. Luckily he refunded me, but after I found out the dealer wanted 67+ tax, I bought a PowerTorque one from O'Reilly for 23 bucks w/ gasket. Parts are getting hard to come by for sure on these older LS400s. It would've taken 4 days to ship from CA (don't know why it takes that long, but that's what they said)

Since I was born in 1987....you got me beat there

RA40

iTrader: (6)

I was unclear, when I was asking about how it felt. This was in reference to the stuff on the transmission filter screen. The ATF dipstick has a rubber seal and as it ages like other rubber-plastic parts it becomes dry and the sealing is reduced. That allows contaminants to enter through the dipstick tube. If the particles are internal from wear they will be like dicer mentions. If it is gritty like sand than I'm thinking the fine grit is coming down the dipstick tube.