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automatic gearbox experts?

17 September 2005
Garden of England
right I have a problem with my NSX.

now i don't want this to become one of the many 'autos are crap get a manual car' threads as they don't help!

i've a '92 auto, 100k miles and the box has gone down. symptoms thus... was driving ok, gears as normal in D, then got to a junction, gently accelerated out and flared into second and lost drive. stick pulled back into 3, still no drive until the engine revs let to idle, and then it 'catches' and i have drive in 3. shift back to D and lose drive again, so limp home in 3. ok so the box is probably worn out, so half expected.

so get a replacement 'low mileage box' as ALL second hand ones are. Fit it and it all works fine, smiles all round, gears shifting as they should, I can even feel the downshifts slowing to a junction (the old box was tired!) but after few miles, i do a turn gently accelerate (easing the new box back into service!) and lose all drive. switch car off, restart and i have all the gears again for about a mile, then lose drive. switch off, restart, and continue the loop!

now i could be unlucky and got a second bad gearbox, but could a controller be the cause? not getting any fault codes up, not flashing dash lights. I have tried a second AT ecu, does the same thing. what else could trip out the box? TCS off still does it.

unfortunately there's not alot on the searches, apart from the one suspected blown by a trackday spin, and all the others suggest a manual conversion...

has anyone got any ideas....

just to add, daily driver, fluid levels good!
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I agree.
Did you find a solution yet?
My car has just done this too and I have had a fully rebuilt gearbox about 18 months ago. I don't think it is the gears but something electrical ?
Me racing down the quarter mile. Who said Auto's are slow. This was on street tyres too.
I have almost same problem - actually identical to one posted by 'my_exotic_princess" owner in 2008. My trans works fine when started from cold. I get about 10 min of normal driving - then jumps to 2nd a few times (going back to normal driving in between) and then decides to stay in 2nd for limp home. If I reset TCM via pulling fuse - goes back to normal for about 2 minutes and then goes to locked in 2nd. Codes = 0700 and 0715.
Have replaced the Secondary shaft speed sensor and the double shift solenoid ...and the TCM module - no changes. I suspect electrical as the shift level lock device is now acting up. I am about to take center console apart to see what is going on in the shift switch area. Anyone with ideas - please send email or phone me. Canada (00's etc) 1 416 409 9889
latest stage i'm at is that the replacement gearbox was a bad one, with, i'm told, water contamination... i'm guessing it was left outside uncovered (with a missing vent cover) before i got hold of it.

it's due back any day (well hopefullt as i've has so many 'ready tomorrow's it's unreal!!!) so i'll keep you posted

the losing all drive, with reference to Kaz on NSXCB, could be down to a blocked filter meaning all pressure is lost, then whatever is blocking the filter moving away when switched off... if it had water contamination there's no clue what could be floating around in there...
a quick follow up, as often threads don't have a conclusion...

after checking everything connected on the replacement box was ok, wiring to the ecu was correct (not broken, open circuit wires) and a reset, i took it for a gentle drive.... that's when the box grenaded itself, to shrapnel in the torque converter levels! so the box was swapped out again, the original back in to keep the car mobile

the replacement box was returned to the vendor to be replaced and i was told about the water contamination when it was opened up.

progress and communication was slow, starting with a lot of 'it's being repaired', moving to we're waiting for parts, and evolving into 'it'll be ready tomorrow'... (1 1/2 weeks of 'it'll be ready tomorrow') then the company not remembering if they were repairing it in-house (what i was first told) to 'they are getting it back from the specialist', I gave up and asked for a refund.. 3 weeks later i got my money back, with no mention of what happened to the box!!

so apart from them telling me it was water contaminated, i found out nothing else about that box.

in the mean time i had my original box rebuilt and refitted, and all the problems have gone, the box is as it should be! so it was just down to the box, and not ecu related at all

BTW.. rockauto are now listing NSX AT rebuild kits, and AT filters... just for reference
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I would not pretend to know what the problem is with your transmission or with the replacement they tried. I'll be interested to see how this goes for you. That said I wanted to just share my observations about Honda automatic transmissions and manual transmissions in general. As a qualifier let me also tell you I am no more than an old shade-tree-mechanic with limited experience; but I have rebuilt a number of transmissions, both types.

My interest in Honda automatics began when I bought an old '01 Acura CL and continued through some other models over the next decade. I've also got a 6-speed manual Honda. I don't own an NSX but no matter which end of the car you put it on the transmissions are going to be basically the same.

So let me say these couple of things about the Honda automatic transmissions. The first is "they all do it", by which I mean that problems with Honda automatics is commonplace across all lines and all models and pretty much all years. The second observation may be of interest to you, that is that they are electronically controlled. The third thing is probably telling but you have to have a little transmisson experience to understand it. Short version is this: nearly all automatic transmission work via nested sets of planitary gear-sets. By nesting a couple of sets of these gearsets with various methods used to lock down each individually you met multiple range automatic transmissions. They are as common a dirt, its how the world builds automatics. But Hondas are different, way different. I have no idea why but for some reason Honda builds automatics that are, essentially, manual transmissions with each gear shifted by an electrical solenoid; initial and low speed clutching is accomplished via the torque-converter, higher speed shifts are cushioned by these sort of intermediate clutch packs between gears. Its really sort of an odd thing. At any rate the common flaw across the various models of the transmission seems to lie in those clutch packs. That said if they are jumping around in shifting you might tend to suspect either the control mechanism (shifter) or the solenoids, and the second/third one seems to fail frequently on other cars. Also, on other model (Honda) cars, there seems to be a common set of problems when they suffer a transmission failure. It works like this. Those clutch packs between gears begin to wear and the debris contaminates the fluid. Most models have no user serviceable transmission filter, though there is one inside the case you could change easily enough. So the junk builds up in the transmission and torque-converter and because many models have small (inadequate?) passageways sooner or later they clog, slip, and fry. Basically once you see symptoms its too late. At least that is how it is with every other model of Honda from the '90's right on up into the middle 2000's. Like I said, I'm no transmission expert, I'm just saying that for some reason Honda seems to make automatic transmissions their own way, not like everyone else, and they seem to all share common problems that sound just like what you're seeing.
yup, honda autos are not like usual autos! it did amuse me with a search here, someone suggested tightening the bands and all will be fine.... errrr... not on a honda/acura it won't! TH350 yes, anything with a honda badge, no!

so, yes they are like a manual, each cog having a clutchpack inside it to do act like a manual gearbox sychro. the torque converter effectively doing the clutch bit. and some hydraulic pistons to do the actual gear selection. Most gearbox 'specialists' here seem to run scared from the honda auto, but they are all on the same principle.

my complete story is on nsxcb... http://www.nsxcb.co.uk/showthread.php?10491-My-automatic-gearbox-the-story!-lots-of-pics-too

oh for an external filter from the factory!

on a side note, i didn't find any info regarding any differences between a normal AT box, and the later flappy paddle version.. i mean as regards gearbox hardware, not extra solenoids/controls. so i suspect it's just the controll system, so in theory you could work out a flappy paddle upgrade...