94 240 conv with AT shift problems

[flint]

Great news, 10 months!!! now since I unplugged the Revolution sensor, still shifting perfectly! Thanks! Flint. secondly, do I need to worry about replacing it since there is a secondary one in dash?

Modified by flint at 2:04 PM 5/14/2005

Modified by flint at 11:04 AM 7/30/2005
Modified by flint at 10:39 AM 12/3/2005

[CDE]

*sigh*

I wish mine was that easy :PI tried unplugging that one but it didn't do squat...I'm finally going to check the tps tomorrow...now that I know where it is :P

[CDE]

I finally took it to a shop because I was getting no where. All my tests were showing the tps and rev sensor to be workin properly.

Turns out, it's nothing electronic and it's nothing external to the transmission like sensors and such. Mech figured it is just a weakening transmission. UGH. I'm praying that he's wrong and that it's the drive shaft some how. It shudders when it's under torque at low speeds - weak U joints. I've had it off a few times - once it helped the shudder, but the second time I took it off, it made it worse. I'm not sure if it's the culprit for the apparent tourque converter 'shudder' (not locking up properly - or so I thought). does anyone think it could be possible?

When it was at the mech shop he added some anti-friction atf. it helped the rough 1-2 shift a little but not the (apparent) TC shudder...

[CDE]

Well, I finally figured out what was causing my shaking (when I first take off) - The problem was my steady bearing that is on the driveshaft. The mechanics I had taken it too put rather large dots on the driveshaft and bearing so it wasn't lined up perfect. Just being out an 1/8th or a 1/4er inch caused a rather annoying shake. I'm sure it has alos fixed or at the very least improved my shimmy that I was experiencing once I would hit 80+ km/h.

This is just for a reference if someone else is having a shaking problem when they are first taking off from a stop, and possibly the shimmy at higher speeds.

Just take a string and make sure the shaft is lined up properly measuring it from the center of the circles on the u-joints. Just loosen the 2 bolts (see pic) and twist the bearing until the shaft is aligned properly. The bearing isn't perfectly round so just twisting it will make a difference if the shaft is strait or not. Just putting dots on the pinions and bearing were not good enough to get it perfectly strait. Use a string

Specs:1989 240SX coupe24KAE (SOHC)Automatic

Hope this helps anyone else with this problem so they don't spend 5 months trying to figure out what the heck it was...



I apologize for the crappy picture, but my car is low, and my batteries died right when I took that pic so I couldn't get a better one... But that's the steady bearing.
Modified by CDE at 11:59 AM 7/17/2005

[blues14]

my 89 240 is doing kinda the same thing. except my biggest problem is the car decides to not start out in first gear once it is warmed up. also, the gear selector will not go into D1 position.

[tumolt]

Thanks to you all for the information. I just inherited my 82 year old mother's vert with 79K miles. While driving it I recently had the transmission hang up in first gear. What the heck? After joining up with this site I fell into your quest to find answers. I am taking your advice and disconnecting the Revolution sensor and cleaning the contacts. I hope to report similar results. Thanks, Matt

[tumolt]

Well I ordered the revolution sensor, it should be in by Wednesday and my friend will install it for me. I disconnected the plug as shown and am able to drive the car but still I have intermittent problems with the shifting if I accellerate too quickly. When I drive slow it seems to work (more or less) I will know more after the new rev sensor is installed. I wonder if there is a key code to resetting the transmission since it is computer controlled. Anyone have thoughts on this before I get the part? Thanks, Matt

[jackchoo]

anyone there who can help?? This is a S13 Auto transmission by the way...

update : I notice that it happens quite predictably :-

- from a cold start (after 2-3 minutes warm up)- after 6-7 minutes of driving- at that point I'm normally in heavy traffic so coasting real slow towards the freeway entrance- enter freeway, accelerate- and it cannot get out of first gear!!!- stop the car dangerously by the side- and its all ok for the rest of the journey! till the next cold start go back to the top.

It pulls out a code 43 when this happens (TPS) for the TCM and ECM. But I've already swapped with a good tps and have even checked it on a scope first.

One question though : is the TPS harness 0V reference supposed to be directly grounded to the battery. My multimeter seems to show a direct short to body/battery ground.

[oldbald_sarge]

I hate to see you in such pain. Refer to nistech reply of 4/6/2005, 6:29a.m., pull the sensor, it works immediately. You will be amazed, as everyone else was.

[jackchoo]

ok i will try that. But still weird that the ECU pulls in code for the TPS...

[jackchoo]

tried this fix....no more gear stuck for the past 2 weeks. Thats a big improvement! So the next question is, why would I need to replace the revolution sensor? I suppose its there for a good reason......and anyone know what part number is it? I'm thinking of getting it changed..

[NISTECH]

The car has reverted to the speed sensor for shifting as a back up. If the speed sensor glitches you will get stuck in third gear and there is no back up at that point. Taking off from a stop in third gear is no fun, especially in heavy traffic. The car is in a failsafe mode now but not as drastic as if you had nothing. This would be the reason to get the other opne replaced.

[jackchoo]

anyone changed theirs yet? should I try cleaning the connectors first?

Appreciate if someone can show me exactly where its located....?

[jackchoo]

ok so with the rev sensor disconnected I find that I get poorer fuel economy. Used to do 10 days on a tank now I only do 8days (for the past few weeks).

Anyone fixed the rev sensor or got it changed successfully? any advice appreciated before I go out there and buy one....

[idrow]

This problem has been haunting me since '99. I have 2 240sx convert's (92 & 93) and both have this shifting issue. It's annoying as hell. Other than that, they run like tops (one has 234k and the other has 102k). I can't wait to try the revolutions sensor solution. I'll let you all know how it goes. Thanks to all who worked so hard at finding an answer to this! I pray this fixes it for me.

[jackchoo]

update...was planning to change the sensor so the transmission shop dropped it to check on the part. They took it out, put it back and said they need to order the rev sensor and it costs about USD200 for the part. I told them I'll try to source for a cheaper one and they put everything back, FOC.

It has been 3 weeks now, with the rev sensor connected again, no re-occurrence. If you guys can access the sensor itself, perhaps its a good idea to give it a good clean + the connectors and harness nearby.

If it fails again, I'll do it once more!

[kornaz]

Funny thing, but i had a 93 Conv a year ago and i had EXACT problem. But mine appeared whenever it wanted - not after exact time or being cold. Just wouldn't shift to second gear. It was embarasing going home 7 blocks in first gear lol. Sold it a bit later

[NISTECH]

In the event of occurance , throw it in neutral and let the rpms come to idle for a few seconds, throw it back in drive and it SHOULD start shifting again. Works on mine every time. YES I know what your thinking, "your car does it, you know how to fix it, your a tech and can do it pretty easily with a hoist, yet you just let your car do it?" The answer is YES. I know it wont hurt anything if I work around it when it occurs and just let it go, besides I am throwing a manual transmission in it, which by the way I have all the parts to do it, I just cant get myself motivated to actually put it in. Its not a paying job....lol

[onosqv]

Anyone have a better picture of the rev sensor location? ... & # of wires on that connector? I see several gray connectors by the fuse box .

[240SX@MD]

Hi,

First of congrats and thanks for the great help to all involved in this issue!!, i just finished reading it and as you'll read below my transmission showed it's first symptom a few hours ago...

I have my '93 240SX for about 7-8 months now. The first problem i encounterd was the roof leaks. So i finally replaced my convetible top this week. I pick it up today after work (it is so nice to be able to see through the back window again.) And on the way home turning right after a red light my transmission would hesitate shifting to 2nd and then would not shift at all.

Great I thought, i just fixed my top and now the transmission doesn't shift. Pulled over / turned on the hazard lights and let it idle on P, then I cycled through R N D 2 1, for a few secs on each gear, something similar as NISTECH described two posts ago. Then put it on drive and no problems at all on the way home.

For stats and history it was about 32F around 9pm here in the DC area.First thing as i got home, log in to NICO Excellent write up!!! I know now that it will happen again sooner or later, so I will I do the recommended check ups and keep posted for the outcome. Question, how often do you change AT fluid (drop pan/change filter/clean magnets/put new gasket)? on my previous car I used to change it every 30K mi.

Many thanks, regards,

Luis.

[240SX@MD]

CDE: I have the exact same vibration (shimmy) problem.

I have the shaking and shimmy at high speeds, yes, exactly at 50mph (or 80kph +) mine does the same, and it its very annoying. I have replaced all my tires and balanced/ and rebalanced... And I was about to put new bushings all-around as someone told me. But I'll try the driveshaft aligment first as you mentioned. Can you show a wider picture, maybe the whole drive shaft? and which bearing should i turn/twist? Thanks in advance. Has anyone experienced this shimmy at cruising speeds before?

Sorry, I know it is not on the right topic thread.

Thanks again,

Luis.

[nissanconvert]

I just bought a vert and mine shakes at around 60mph or so, I took it to get rebalenced and the guys at the shop said one of my rims is bent and probably causing the shakes. I got a new rim but haven't had it installed yet to see if it worked. It probably not your problem but just thought i'd throw it out there anyway.

[Florida240sx]

If anyone can get a pic of the sensor.I'm confused on it's location.Got pulled over the other day for when it revved up and then shifted at abotu 7500rpms and tires broke loose as I was turning.

[S13inBatnRuge]

i have a '93 coupe and mine was on the left side of the car ( standing in front of it, not sitting in it) in a group of wires near the right strut tower. it had a group of three gray connector and one brownish/red connector. look for the three pin connector. and remember when you start your car it will flash on your o/d light a couple of times.
Modified by niteboo at 7:43 PM 11/20/2005

[S13inBatnRuge]

had the same problem. unplugged it last friday and hasnt missed a beat yet.

[240conv]

please pay attention your problem is the rpm sensor mine had that problem this site told me about this disconnet it, it is there on your left side when opening your hood,there are 2 or 3 that look alike when you disconnect it it shifts perfect.

[donmeca2020]

so is this only happening to people up north where it gets very cold or what? when we went to test drive the one we're about to pick up it was cold and had no problems with the transmission shifting. let know about this. because im in the more warmer climate and would like to know if i should worry also.

[idrow]

Well, I finally disconnected the revolution sensor this weekend - no good. Once I did that, it wouldn't shift out of first. Sigh. It's amazing that this seems to be a universal problem with these cars and that there isn't a concrete diagnosis and solution. Sigh. Love the car, hate the transmission

[hatchback240]

a couple of things of input:-to answer donmeca2020's question, no, its not a northern thing, i live in abilene, tx, and my 93 hatch started acting up on me not 2 days after i got it.- thank you to the major benefactors who made this discovery happen, my dad was about to put my 240 in the shop, im so glad i found this!! we have enough money to get by, but not enough to replace a transmission, or have it rebuilt. you guys deff made my night -im not 100% sure i disconnected the right sensor, under the hood, between the pillar and fuse box there are three sets of connections, one is red, its the bottom set, then there are two grey connections above that, i disconnected the middle. my car runs alot better, no sticking, but it does seem to shift different, it would upshift and downshift at particular speeds, say 3-4 at 40mph, and 4-O/D at 60mph (atleast i think thats how the gears work, but the speeds are correct).

any input would be greatly appreciated, again, thanks for everything!! life savers

[bankrup3000gt]

I live in Tucson,Az and it happens to mine once in a while. Hasn't tried any fixes. I don't drive it much. Wife's car and she doesn't notice it as much as I do.