Editing Forums/Z31P/z31-performance-upgrade-forums driveline-aa/transmission slipping/not shifting

{{ForumImport
|op_user=th3gentlegiant
|op_date=2013-06-24 23:53:13
|post_count=23
|archive_url=/Z31performance_archive/forum/z31-performance-upgrade-forums/driveline-aa/21895-transmission-slipping-not-shifting.html
}}

'''th3gentlegiant:''' <small>(2013-06-24 23:53:13)</small>

just bought a 87 zx the other day, and i took it for a drive today, and the transmission wouldnt engage in anything besides 1st gear. maxed out at 35mph at almost redline. i can accellerate, it goes to redline, and i let off the gas, the rpms drop, and when i get on the gas again, it goes to the rpm i let off at. it sometimes wanted to grab a higher gear, but then when any decent force was put on, it skipped out and would rev until 1st engaged. at one point the car was shifting properly and no slip, but after shutting the car down and letting it sit for a few minutes, the problem came back. does this with overdrive on or off. i think it is the transmission module since it was functioning properly at one point, but i would like some clarification if possible.

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'''G-E:''' <small>(2013-06-25 00:09:59)</small>

If a fluid flush & filter won't fix it, you need a rebuild, a replacement, or a 5-speed swap…

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'''reddzx:''' <small>(2013-06-25 00:52:55)</small>

A fluid flush & filter won't fix it, your friction disc's are fried. Don't waste money on trying to bring it back, it won't. As said already, "you need a rebuild, a replacement, or a 5-speed swap".

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'''th3gentlegiant:''' <small>(2013-06-25 04:49:45)</small>

put a good amount of miles on it after this post. i forgot to mention the car had been sitting untouched for over a year in a barn. i started and shut off the car a lot during the time to test the amount of time it took to get into shifting. my original thought was the modulator, but i think otherwise now because once it begins to shift, it does so until the car is off. im going to be doing a filter/fluid change asap and im thinking that will solve my problem. i think the filter was gunked up from sitting and just needed to be worked a bit and freed up. the last time i took it out after sitting for about 20 minutes, it took about a minute to start shifting compared to 5 minutes when i first started driving it. i think it is just the fluid and filter

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'''Dave-D:''' <small>(2013-06-25 12:43:31)</small>

If you have no idea how old the auto-tranny fluid is or how long it sat unused. Do a flush and fill with the right fluid. If that fixes your shifting problem, great. If not, your only out a small amount of time and money on fluids. Also get that timing belt, tensioner and water pump done as soon as possible if your not sure of the age or condition. These are interference engines, lose the timing belt, even slip a tooth or two, and you can kiss the valves and pistons goodbye as they destroy each other.......Not trying to alarm you but it is probably the #1 engine killer for these cars. Better safe than sorry. And again its not really difficult to do, unlike some of the guys here I am not a professional mechanic just a guy that likes to mess with cars. I did my own with am FSM, info from this site, and Xenon's website [http://www.xenonz31.com/timingbelt.html http://www.xenonz31.com/timingbelt.html] in the driveway in a single afternoon.

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'''th3gentlegiant:''' <small>(2013-06-26 00:17:33)</small>

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the timing belt is next on my list after the transmission is fixed. picking up a filter and fluid tomorrow. the fluid level is quite high for some reason, and i havent seen a shift into 3th yet, but the shifting has been more consistent lately. once the engine is warmed up, all it takes is one good hard push to ~6k rpms, and it usually starts shifting somewhat normal. it seems a tad late from the other transmissions ive seen, but thats probably due to the fluid level and filter

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'''reddzx:''' <small>(2013-06-26 00:46:01)</small>

Trust me, its not gonna get better on its own. The fluid level is high because someone tried to "make it work" by adding fluid. You can waste a few bucks on fluid and filter just in case you get a miracle though. I've owned three auto turbo car and I have a little experience with them going bad and having them rebuilt. They are expensive to rebuild, $1500-$1700 and you can buy all the parts for a 5 speed swap for around $500. If you are determined to stay with an auto trans, (I have one auto turbo car I don't plan to change) either find a low mile unit and do a partial repair with a shift mod or totally rebuild yours. If you ever overheat your car to the steaming, spitting point, immediately change the filter and fluid or its toast. 84-85 auto will not work in 86-89 due to the electronic shift system. It can be made to work so some say but I don't know that and my trans re-builder said he would not warranty such a swap.

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'''Pdfflyer:''' <small>(2013-06-26 02:03:28)</small>

Automatic transmission just pulled from my 87 Z31 Turbo car.

Could be yours, can you pickup in northwest PA or arrange for shipping.

It is on a wood pallet, ready to go

Pdfflyer@Roadrunner.com

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'''Filipe:''' <small>(2013-06-26 11:11:04)</small>

PM me if you need parts for the timing belt change.

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'''th3gentlegiant:''' <small>(2013-06-26 23:14:00)</small>

Did the filter and fluid today. Put in 7 quarts And it still read over full and the problem continued, if not worse. Before once it shifted it stayed in the gear now it will shift, but slip out and go back to 1st. Did get overdrive to work for a little bit though. My guess is a valve or something is stuck or clogged inside the transmission. Going to be replacing the modulator and vacuum lines tomorrow and see if that works. Otherwise, I may be doing a 5 speed swap sooner than expected. Also found some slop in the transmission. Got the back wheels off the ground and turned them back and forth, and the whole driveshaft was solidly tight and the splines coming out of the transmission turned a minor bit. Not sure if its due to the fluid issue, or something wrong internally.

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'''G-E:''' <small>(2013-06-26 23:34:54)</small>

Your valvebody probably collected a bunch of dirt with the new fluid… I did this on a caravan I had, everything got worse for the first week, then it started clearing out, after 2 months it behaved better than a "rebuilt" trans of the same generation in my mother's caravan

I ended up donating my trans to someone else's caravan when I finally gave up on the vehicle (someone rammed a door, fuel pump died etc..) and it went another 80k kms (290k kms when I gave it to him)

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'''th3gentlegiant:''' <small>(2013-06-26 23:48:26)</small>

So basically I should see if it will clear itself out before buying a modulator?

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'''NissanEgg:''' <small>(2013-06-27 20:44:44)</small>

Correct the fluid level asap. Over filled autos will aerate the fluid and damage components from excessive slip and will also burn up the fluid in no time. Air compresses, causing slip, fluid does not compress. Fix the level first and see what happens.

Trans need to be warm, in P or N with engine running to get proper fluid level readings.

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'''th3gentlegiant:''' <small>(2013-06-27 22:33:32)</small>

I think I found the issue. Transmission worked flawlessly earlier today after checking the vacuum line to the modulator, but after driving a bit and letting it sit, I think the vacuum line vibrated itself a little loose, and isn't getting the proper seal to allow the transmission to work properly. Going to find a new segment of hose to try and get a better seal on the modulator and see how that works .

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'''th3gentlegiant:''' <small>(2013-06-28 03:13:57)</small>

so the problem continues. when the car is cold and just starting up, it shifts and everything works flawlessly. but after it warms up, if i shut the car down and start it up again, it goes back to the original problem of staying in 1st gear and when it does shift up, it slips out easily. not sure why. its beyond my knowledge..

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'''NissanEgg:''' <small>(2013-06-28 13:01:52)</small>

Correct the fluid level first and foremost on any automatic transmission before conducting diagnostics. If not, you will be chasing your tail forever on this.

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'''th3gentlegiant:''' <small>(2013-06-28 16:50:19)</small>

a friend also recommended stop slip additive? it seems to have mixed reviews from the research ive done and only for a short term fix before making everything worse. would it be best to just leave it out, or give it a go

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'''reddzx:''' <small>(2013-06-28 17:25:53)</small>

It might be good enough to help you make it to the transmission shop. There really aren't many solutions when these auto transmissions start to fail.

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'''FrozenZ:''' <small>(2013-06-28 18:38:04)</small>

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+1. The good news is that a rebuilt one will probably outlast anything else on the car. The bad news is that unless the body is absolutely rust-free and you really want an automatic z31 (when some idiot hasn't overheated it the auto is actually totally solid and a perfectly good tranny for a DD, especially if you have to drive in traffic a lot - I decided to keep mine in my 84) you'd be nuts to put that kind of money into that car.

Think pretty hard about what you want to do here… the 5-spd swap is not really a good "my first big car job" if we're talking about the car you need to get to work and stuff. You might be better off getting out of this car before you get further in money-wise…

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'''G-E:''' <small>(2013-06-29 01:50:07)</small>

Guys stop being so apocalyptic on the guy haha

He clearly said the problem comes and goes, that leads me to think it's not a friction issue, but rather a line pressure issue leading to improper clutching/lockup.. lucas and amsoil both make additives that improve the friction and anti-aeration qualities of the fluid, considering the age, this won't hurt to try

But my suggestion as before, is keep trying to drive it, and see if it gets better, it takes time for new fluid to displace all the crap from the valvebody

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'''reddzx:''' <small>(2013-06-29 03:59:49)</small>

NO, its the end of the freakin world already.

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'''Crazy:''' <small>(2013-06-30 01:06:38)</small>

How many miles? Any fluid leaks?

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'''th3gentlegiant:''' <small>(2013-06-30 22:32:12)</small>

replaced the modulator yesterday. problem is going away more and more. but it seems to be now that after the fluid change, my speedometer is cutting in and out and causing the transmission to shift when it isnt needed. think the speed sensor might be going? there are some sketching looking wires underneath that i have to tidy up a bit, and hopefully solve that issue. but the transmission is working properly for the most part (minus the first 30 seconds of movement where it doesnt want to shift). might be the speed sensor reading the speed incorrectly and making the car think its going a different speed and not going to shift. because when it does work, the shifts are smooth and stay in place well.

and btw, this car is solid. 158k miles, no leaks, garage stored for a long time, minimal budy rust (minor spot on driver side rear quarter panel and around the antenna) but almost perfect body wise besides that, minor spots of rust underneath but nothing structural, and then minor issues like bushings, cracked tail light, power window assembly, etc need work. i wouldnt have bought the car if i didnt feel like it would be a good car for me to have for a long time and to care for/build up over time. yes its my first car, and i may end up putting "too much money" into it, but i want to have a car i can get my hands dirty with, learn the mechanics of everything, build up, and feel proud of when its finished years from now. all these "you are going to put too much money into it" comments just get skipped over. i just need to make this transmission last long enough until i can afford a 5 speed swap. if i end up putting tons of money into the car, oh well. i love it. it has its quirks. and the quirks are why i love it. theres something that draws me into the car and makes me want to drive it everywhere. no other car ive been behind the wheel of do that like this car. so if it takes some money to get it running perfect, so be it.

EDIT: found a wiring nightmare underneath. melted wires, wire nuts, etc. wire from the speed sensor was melted, wires coming from the overdrive controller were spliced and wire nutted, and so on. going to be cleaning up all the wiring i can and see how that works. already fixed the wires coming from the speed sensor, and the speedometer has been working fine and the transmission seems to be working better as well. takes one good hard push when first starting off to get the shifting to start, but once it does it shifts smooth and acts like it should when the car is moving. still has some slip when accelerating from a stop (alot like a newbie on clutch that waits too long to release it), and some hard shuttering from the transmission wanting to grab and worn out suspension bushings allowing everything to move around like crazy. but its enough to get me where i need to go until i can afford to replace it with a 5 speed. will be replacing the fluid again within 3k miles to get as much crap out as possible (drained some out when i replaced the modulator to have it at the proper level since i didnt do a fluid flush, just a drain so it was actually overfilled a little bit and it was a pretty dark red color) and might add some stop slip or tranx additive before that fluid change if i can find one that has had consistent positive results.