Hello! New to forum and recently bought a 91 ls400. 153k miles. The transmission slipped once so I decided to bring it in and have the transmission fluid flushed. After having it flushed, it drove just fine for about 30 miles and starting slipping horribly. Now it's just parked. I'm wondering if I should:

1. Replace transmission
2. Flush Transmission with Toyota IV fluid at Toyota/lexus dealer

I had brought it to Sears auto center and had it flushed. i called them and asked them what fluid they had flushed with and they claimed it was a universal transmission fluid, which ive never heard of (or the lexus dealer). the fluid was terribly dirty before the flush. It is still a red after the flush. I'm not sure if it's worth the $200+ to have it flushed with the proper fluid if the transmission is in fact bad. It shifts ok when pulling onto the road and then will eventually stay in a certain gear. When warm im driving home in 1st gear sometimes. This area on the eastern coast of Oahu is all 35-45mph and it needs to shift several times to drive.

 

All Lexus transmissions are TERRIBLY sensitive to the type of fluid used. You need to have whatever they filled your tranny with flushed out once again and refilled with Toyota Type IV fluid. Only other non-toyota fluid I would use would be by Amsoil. The wrong fluid type in these transmissions CAN cause catastrophic damage and you will not be happy about it. You can pick up the Toyota tranny fluid from any toyota dealer(cheaper than going to Lexus to get it). This is what you need,,,

 

Read a thread about a wire harness at the drivers side trunk lid. Sure enough, that's the problem! Looks like the wire was crimped tgether before but was pulled apart! The guy who sold it must have thought he totally screwed me. Thanks Lexus Forum!

 

The wire harness is also another area for problematic solutions. LOL!!! Good deal, and glad you found it. But STILL get that "universal" stuff outta your transmission. Like I stated, it is def no good for it.

 

I use Mobil One synthetic trans fluid and have 234.000 miles and no problems. but using type 4 made by toyota will also work real well also if the trans starts slipping again the next move is to see a good trans place and let them look it over.

 

From my experience I would support this.....
Never.... Ever, Ever use any other fluid other than TOYOTA T-IV in an LS400.
I you do so, it will act like your transmission needs to be replaced...
Change the filter and oil.

 

And never ever have a place like sears do anything with the transmission. Either a dealer or a super reputable transmission shop or Lexus independent.

Oh and if they ruined the transmission they should be paying for the fix.
Always Always make sure the service manager or someone important goes for a ride or drives the car with you so they can see it is working good, before it goes in the shop for transmission fluid changes. And have them give you a written something saying that it was pre driven. Other wise they can just say it was slipping before we did the work.