hard shifting tranny

[philrod51]

I have a 2000 safari and when it heats up the shift from 1st to 2nd happens with a bang. Anyone knows what causes this to happen? I had a filter change done and exchaned all the fluids at Mr Lube and the problem still exists Truck has 280k kilometres. Thanks

[WoodButcher]

Is the engine light on? Are there codes? 1870 maybe?

The computer sensed slippage, probably in OD on the highway, sets the 1870 code and increases the trans fluid pressure to save itself from further damage. Clear the codes, 1870 in particular and the hard shift will stop. If it returns as it will likely in the not too disant future you will have trans repair to do.

[MountainManJoe]

You can give these charts a try:
http://bit.ly/sFxFzQ
http://bit.ly/uzvSjZ

[LiftedAWDAstro]

It will do that when the trans gets too hot. Install a monster auxiliary trans cooler and it should help. Also keep servicing the tranny every year or 2.

[MountainManJoe]

I can believe shifts becoming harsher when the ATF is hot, but I've hat the fluid very hot at times and it never 'banged' as OP describes. The VCM should be able to compensate for temps. This sounds a bit more serious and 280k is a fair bit.

[brokenwrench]

The usual problem.......

As noted, when a disparity is noted by the PCM between converter clutch speed and
input and output rpm., the controller compensates by increasing line pressure. Usually this is caused by converter clutch failure. This usually is caused by bore wear in the valve that controls converter clutch apply.

The code sets in OD when the ratio between converter clutch rpm and output rpm widens.
The valve body contains the controlling valve.There is a "isolator valve" and a Torque Converter Clutch regulator valve. This wear causes pressure to drop and slippage to occur.

To further complicate matters, there is an "Actuator Feed limit valve", this too can wear. The converter lockup switch can also fail, but this is more absolute.

All the major aftermarket companies make repairs parts.There are either reamers and oversize spool valves or various "stuff it in the worn hole" kits with sealer rings.

The usual fix is to rebuild the valve body, Trans go makes a shift kit that cures the problem if one of the valves are worn, I would have to look up which one.

If you have functional OD this will help to guide what to do,

easiest fix is to put in a new valve body, if you wait too long you will start to break hard parts.

[BREAK]

I know this topic is a month old now but I had the same problem and was able to fix it with a transgo shift kit and an auxiliary cooler.
The kit I used is designed specifically to fix the hard 1st to 2nd shifts. Mine was so bad it was definitely going to drop the driveshaft or break the ring gear. It's been working the way it's supposed to since fixing it.

My topic: viewtopic.php?f=57&t=5183