lock up on torque converters ???

steptoe · Post by **steptoe** » Thu Jan 29, 2009 9:42 am

Can someone explain how lock up is meant to work on torque converters of say , my 87 Lseries turbo 3 speed 4WD auto . On another post someone mentioned lock up not working on someones (mine?) car when discussing revs and speed.

I have seen 4000rpm at 100kph (GPS accurate) under acceleration and see it drop to about 3100 on light cruise or down hill at same 100kph. At 80kph I see 3000rpm under acceleration turn down to as low as 2300 or 2400 downhill.

Should lock up occur at a speed and lose it under acceleration , or NOT?

This tranny needs to be warmed up after sitting for more than an hour if I wish to move. If I put it in gear and accelrate without the warm up it just crawls until a pressure builds up somewhere. Think the clutches are OK as I accidentally for the frst time found kickdown from top third to second at about 80kph and got a chirp outta the tyres, well one anyway

vincentvega · Post by **vincentvega** » Thu Jan 29, 2009 10:01 am

sounds like the box is on the way out. You should get drive instantly on a cold box. Something is not happy in there. Your "chirp" only tells you that one set of clutches in there is OK.

your 3100 - 4000 rpm range means the converter is not locked.

the 3 speed auto is a mechanical box that I dont know a lot about. convert to a 4EAT if you like autos

Gannon · Post by **Gannon** » Thu Jan 29, 2009 4:50 pm

The 3AT has a normal torque converter, which at best has 5-10% slip between input and output.

When you say it does 4000rpm under acceleration, are you sure its not kicking back to 2nd gear?

Travelling on level ground, crusing at 100KmH should give you approximately 3200rpm

If not, how old is the transmission fluid?

The later 4EAT has a lock up torque converter that locks the input and output shafts (0% slip) under cruise to improve fuel economy. The lock up function is controlled by the TCU

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Thu Jan 29, 2009 6:59 pm

Steptoe, those figures are about correct for the auto in question but the warm up period sound like it needs a good service (pull box from car and pull apart) The auto RX is about 3300 at 100.

steptoe · Post by **steptoe** » Thu Jan 29, 2009 10:14 pm

Well thats what I wanted to know - lock up converter not on the 3 speed. The auto has been like it since I got the car with 188,000 km on it and clocked over 208,000 the other day. Auto fluid has not been 'changed' as such, since ownership but it has been topped up a few times as the auto fluid is getting into the front diff and getting out the axle seals. I did not like autos, I did not like sedan, I did not like L series, I did not like four cylinders and did not like Subarus much if at all....but now beginning to think I am a bastard to canibalise my GLTA to eventually make a better Brumby. It is all growing on me a bit. Still don't like autos because I never really understood them apart from fluid and filter changes. This one never got a look into as aftermarket service kits not available ? and the genuine gasket is about $40 plus fluid and I have a manual box to fit up first if I can get around to get before it donates its bits to the Brumby. This box if it is ever to come out before scrapping will not go back in. I am curious to see if I can rebuild it and it goes better but the time will never be there.

It is not kicking down from top to second just acceleration with boost the tacho goes up and speed catches up !!

Sometimes it will hang on to 2 before top if pushed and needs easing of acc pedal to shift, also have the suspected weak valve spring that can come into play as well.....

So there is some slippage, not likely to be healthy normal so no long distance trips until I at least fit up manual.

ta,