95 SC to 93 LE Auto Tranny adaptation.

[scottamann]

Got a 1993 Previa LE that lost its torque converter with 195,000 miles on it. There are chunks of metal coming out of the converter. Tranny should be an A46DE.

I have access to a 1995 Previa S/C LE, and have the thought of just replacing the TC from one to the other. Howsomeever, the S/C tranny is a A340E. Torque converter is larger (but still fits the A46DE bell housing and ring gear bolt pattern from what I can tell.)

Question for someone with more experience than I: would you just try to make the TC work on the old tranny, cleaning out the filter, etc? Or would you think that maybe the 1993 tranny had had enough, and attempt to adapt the 1995 tranny to it? If bits of metal were flying around inside the 1993 one, I suppose the filter should have gotten them, but I don't know if that's always true.

The A340E has:
- a different output shaft (use the 1995 one, the differential connection is the same)
- same connectors in slightly different places (wire harness will reach)
- oil cooler lines in slightly different places (use the 1995 ones connected to the rubber hoses)
- different neutral position switch (use the 1993 one to keep the connector the same)
- different rear mounting system (but it should go on the 1993 frame fine)
- different exhaust hanger (use the 1995 one or adapt, one hole in the new housing is threaded, could just drill out)
- etc.

It seems like physically it would work, but what about computer/electrically? Is there a fundamental difference in the SC horsepower vs. the LE horsepower that would make it not work?

And input gratefully accepted.

Scott

I'm not a mechanic, I just have 2 attributes. Some small fearlessness, coupled with lotsa perseverance.

[timsrv]

Another possible issue to consider is the gear ratios of the transmissions. I'm not 100% sure the transmissions have different ratios, but I know the FGR (Final Gear Ratio) is different on the rear ends. Naturally aspirated Previas have a FGR of 4.300:1. Super charged Previas have a FGR of 3.727:1.

As for the transmission with all the metal in it, I would consider that one toast. You might get lucky but I wouldn't trust it. All things considered, I'd try to find a good used A46DE. You might check one of those Jap engine places or maybe even eBay. Tim

[scottamann]

Thank you for that. I hadn't thought about the gear ratios and the advice on the little flying bits of metal (though I don't think the oil circulates in the TC, it just fills it, right?)

In each gear, when you multiply out the FGR with the tranny ratios, you have 1st- 12.5% over stock, 2nd- 5.2% over, 3rd- same as stock and O/D- 3.5% under.  Not so bad and probably something I can live with until I 1) get a good used A46DE (living in Hawaii, that's problematic since no one wants to ship here) and 2) maybe I'll treat it like an X project and try to rebuild it myself. I'm still in awe of these auto-tranny things.

But at least the car will be running, if not as optimally as usual. Shorter first and second gear will maybe make it seem a little more snappy? Dunno if I got that right or not. Hopefully the computer will "do the right thing". Fingers crossed.

Thanks again.

[timsrv]

Let us know how it comes out.

[scottamann]

Well, I surprised myself. It worked. "Stunned and happy" best sums it up.

The A340E does in fact replace the A46DE with minor modifications to the external mounting and wiring. The exhaust hanger bracket is a non-starter because the exhaust system and bracket-to-tranny on both cars is different, but that can be cobbled together with some bolts/all-thread that should do the trick.

It winds out a little more in 1st but otherwise it has smooth and easy shifting. I haven't figured this out, but hard acceleration in it is less smooth than easy acceleration. And it'll pop down into 1st at a much higher speed than the old tranny would (28 mph was the cut in while slowing down for the old one. I got the new one to pop in at around 45 mph - I quickly shifted up. It was going to be a little too much engine roar for me.)

Thanks again for the advice, Tim. Not trying to use the old tranny as is I think was really wise. I also want to thank some other poster's on this board for their manao. Their suggestions for mating the torque converter, cleaning up the oil seal surfaces, etc. were all things that I followed in the pursuit of not wanting to "do it again." which some of them had to do.

Scott

[timsrv]

That's great to know. I know the SC transmissions are built tougher due to the additional torque the SC puts on the drive train. I had briefly considered switching mine over some day, but so far my transmission is still hanging in there. At least now I know it's possible. Thanks for your contribution to the board. Tim