Problem with the gearbox on a 1995 Lexus LS400: it doesn’t move in drive, but it does move in reverse.”

[Frangijon]

Hello, my name is Frank. I’ve bought a 1995 Lexus LS400 with a transmission problem. When you shift into reverse, it engages normally and you can drive without any issues. As soon as you put it in reverse you feel a small jolt, you release the brake and the car moves without a problem. You can accelerate and it continues moving fine.
The problem appears when you shift into drive. The engine revs up, but the car doesn’t move, no matter if you try starting in “1” or “2”.

The seller’s son told me that for a while the car drove perfectly, until the forward gears started slipping, but he doesn’t know anything else.
If anyone familiar with these transmissions can give me some information, I would really appreciate it.**

 

[P Bateman]

Hi Frank,
From the sounds of it, you have an internal failure.

If you can select reverse, then there is oil pressure to some extent, and the gear selector mechanism is working.
Probably wouldn't hurt to check both though.
Dip the oil to check the level and condition.
Get under the car and make sure the gear selector rod and lever on the gearbox are moving properly.

If the issue was electrical, you'd still be able to get some gears when you manually shift it into 2 and 1.

Looking at the holding device chart (below), Clutch C1 is engaged in all forward gears and if its cooked, you won't have any forward drive.
I'd suspect the seller's son may know something... but isn't telling you.




PB

 

[Frangijon]

Hello, and thanks again for your reply. Let me explain the situation regarding the purchase of the car.

The car has 250,000 km now. In 2007, at 186,000 km, the transmission was repaired. Later, in 2011, at 215,900 km, the valve body was replaced. I bought the car at 250,000 km.

The previous owner passed away, and his son told me that he used the car for a few weeks while his own car was being repaired. According to him, the Lexus was driving perfectly, but when he went to return it, the transmission started slipping.

The father changed the transmission fluid before I bought it. The ATF in the car now is clear, but it feels very thin. I suspect he used Mercedes automatic transmission fluid in this gearbox. I also think he changed the fluid because he often bought used Mercedes cars with non-working automatic transmissions, and many times just replacing the filter and the fluid made them work again. But in this case, it didn’t solve the problem with this transmission.

 

[Frangijon]

So you think it could be an electrical fault, or more like a loss of pressure due to some internal seal? I’ve tried starting in first and second gear, and the car revs up but doesn’t move. A couple of times it did something I’d like to explain to you: you put it in R (reverse) and it moves. At that moment, you shift to N (neutral) and then put it into D (drive), you accelerate, and it moves about 20 cm. After those 20 cm it’s as if one gear slips out of another — it gives a jolt, like a clonk, and stops moving. It stays in drive and the revs go up, but the car doesn’t move. What do you think?

 

[P Bateman]

If you disconnect the wiring connector from the transmission, you should still be able to engage gears - the manual shift valve is connected to your gear shifter inside the car via a control rod. This test isolates the electrical system as a cause

P = P
R = R
D = Overdrive Gear
2 = 3rd Gear
1 = 1st Gear

The fact your car isn't doing anything in forward gears tells me the issue isn't electrical.
Look at the table I posted earlier - specifically the No.1 and No.2 Solenoids.
If they are both OFF (because of an electrical failure), the transmission should be in Overdrive

PB

 

[ivan129]

Hi,
Patrick is on the money here.
The symtoms you described sound like it could be the transmission is low on fluid, pump's nackered or the filter in the pan is clogged.
You can go wrong by adding another liter (quart) of transmission fluid to see if that improves take up.
If this doesn't help then the pan has got to come off anyway and / or the transmission out.
After adding trans fluid be sure to shift the trans through each gear while the engine's running and hold in each position for 30 seconds.

Good luck.