Transmission issues FX35

[crankor]

Welp ofcourse now that i got the overheating issue fixed, why wouldn't a new issue pop up? I have a feeling this is just a low fluid issue but i was doing a longer test drive after fixing the overheating issue and on the highway i pushed it a bit and the transmission bucked pretty hard at 80mph. After that it didn't really want to down shift and once i got off the highway i was shifting into neutral to coast most of the way into a parking lot but it was shifting very hard even at low speeds in the meantime. I let the car sit for about 30 minutes before attempting to get it back home and it was shifting ok after that (i took back roads home) but ofcourse i babied it home. I do have some transmission fluid to put in i got a while back knowing id have to swap some out but i don't really know how much to put in now since theres a chance it's already low on fluid. My year doesn't have a dipstick so i have no idea how to check the current level or if thats even possible. I was thinking of just draining and putting in 5 or 6 quarts since that seems to be the usually amount that gets drained just by removing the plug. I suspected the fluid to be leaking from the line that goes to the radiator since it was covered with what i assume to be transmission fluid unless it was just old oil or something.

[VStar650CL]

Checking or filling from the top isn't possible, because as far as I know none of those 7AT's have a charge pipe like a CVT. However, the "level gauge" is built into the pan, so all you really need is a hand pump with a flexible hose to top it off. There are two plugs in the pan, the front one is for filling and the rear one is for draining. The car has to be level to fill and the transmission should be reasonably warm (minimum 104F) with the engine running. Pump fluid into the fill hole from the bottom until it comes back at you, then reinstall the plug loosely when it slows to a drip. Run it through the gears a few times and then pump in a bit more fluid to make sure the level is good, then tighten the plug when it slows to a drip again.

[crankor]

I managed to easily strip the fill plug on the pan but did manage to get it off with a few quick shots of a torch. Why aren't these just a standard bolt? I managed to find a replacement on z1 i think it was but having to wait several days for one little plug is super annoying. Apparently these are "special" threads? or could i just temp just go to a hardware store and find a close match bolt in the meantime?

[VStar650CL]

Plugs are almost always fine or extra fine threads, and if it's EF then you probably won't find it at the hardware store. On the other hand, I'd be pretty sure the hardware store has a free thread gauge if you don't already own one.

[AZhitman]

With that said, it's silly not to own a thread checker. They're like $20 on Amazon, and I use mine daily (restoration and maintenance).

If someone reaches out to me needing a bolt, nut, plug, fitting or clip (Nissan or Datsun-specific), I most likely have it. But you have to have the specifics.

[crankor]

Never even occurred to me I could get one. I usually just use the ones at hardware stores. Guess I'll see what I can find

[crankor]

I managed to find a small window of no rain and fill up some atf. was about 5 quarts that drained. I'm asking this as a future possibility, So far it's been shifting fine but i haven't been able to drive it alot yet to really know and wonder what the likley hood that if the issue comes back that it would just be the valve body or a solenoid on it that would be causing this issue? There isn't any slippage of any of the gears and that is the first time it's ever done that (after sitting for about 2-3 weeks due to rain and parts delays)


Looks like if i did have to replace it, there are alot of remanufactured ones reasonably priced but ofcourse i don't know about the quality. Also fun fact, i got an amazon transfer pump for this and the thing was smoking like crazy(the pump) by quart 4

[crankor]

Is it possible that that issue ws from air in the transmission?

[crankor]

I took the car for a drive on the highway today and the hard shifting happened again. Seems to only do it at a higher speed shift. I don't know what would be causing this. Once it happens, it shifts hard through all gears. Is that a sign of bad solenoids??

[VStar650CL]

Anything that affects all the gears won't be from individual solenoids or clutch/band packs, it will be from something global that's either affecting line pressure, or causing the TCM to misread line pressure or vehicle speed. Since it did it after a cruise, it could also be from overheating, which may mean a problem in the heat exchanger. In any case, you won't solve it by throwing parts at it. Sounds like it's time for a TCM-capable code reader and some streaming temperature data.

[crankor]

So what steps do I do for heat exchange... it's definitely getting too hot. Is that something to do with the radiator? It did start happening after I replaced it. I did get a new filter and pan but haven't put them in yet. I noticed the fluid was still brown pretty quickly after replacing about 5 quarts ad was planning on replacing more with the pan install.... not sure if that's the cause or if it's something to do with the cooler which I assume is the radiator on my case? It is a brand new denso *shrugs*

[VStar650CL]

Yep, that's way too hot. Check if there's flow through your heat exchanger, and if someone else did the radiator, make sure they didn't install one with no exchanger and loop the cooler lines back.

[crankor]

I pulled the inlet hose to see if any fluid spilled out but I only drove the car for a few min to bring the temp up. I did change out some of the fluid in the meantime which was brown ofcourse. When I get a chance I'll have to remove the fans so I can inspect the return hose. I'll probably shoot some compressed air from the top to make sure it's clear. Not sure how else to know if the fluid is flowing through it. I do plan to still change the filter and check inside the pan for shavings n such. I did a 20 min test drive so far after the fluid change and temps went up to about 152 so far. I didn't do much high revving though until the new fluid works it's way through. Anything in particular I should be looking for or test?

[crankor]

I drained and refilled 5 quarts again to try to clean out the brown stuff more and verified that the cooler is flowing. I wonder if I'll have to try an aftermarket cooler or if it's something else causing it. Def only happens when I Rev in the 6k range that heats it up around 200. Low rev driving it seems to stay around 160

[VStar650CL]

That 152F is fine, and actually anything up to about 200F is fine in a regular A/T. So that Temp1 reading is okay, albeit a little toasty. Temp2 reflects the fluid temp coming out of the torque converter, and your TC is getting very toasty. That generally shouldn't get much above 220F, and around 240F is where you start to cook and oxidize the fluid. Temp2 can go much higher if you're punishing the tran-ny in hot weather, but it shouldn't happen in normal operation and it shouldn't stay that way for long once you get off the gas. The point is, over the course of a decent drive, that's going to start cooking the whole transmission. So you may well have a dying TC and not a problem in the tran-ny per se.

[crankor]

Do you think it's possible there could just be air in the system?

[VStar650CL]

Very doubtful. Open-loop hydraulic systems don't trap air like closed-end systems (i.e., brakes). Following a fluid change, any air is usually gone the first time you run it through all the gears. In any case, cavitation from trapped air has the same symptoms as low fluid, "buzzing" from the front pump. No bees, no air.

[crankor]

I decided to drop it off at a transmission shop expecting to have to replace the train worst case but it does sound like it's just a bad torque converter. I'll let you know how it turns out. Still really weird to me that it just happen to start after the radiator change and the timing stuff

[crankor]

After having a transmission shop inspect the transmission, turns out there is nothing physically wrong with the transmission atm so thats a plus. I had them throw on the new pan i got since why not and they didn't see any shavings. They mentioned the fluid was a little low and dirty but thats about it. So after that, im prob just going to get an aftermarket transmission cooler to be safe. I did notice the car has been driving at a pretty low rpm (1000-1200ish) at around 35-40 mph and noticed thats when the temp seems to jump up the most and wondered if its that extra load doesn't help with the heat build up. i did get up to 192.5 ish on my drive home but didn't really go past that with normal driving and didn't do the hard gear shift that it had done before at just 180ish. Is it possible for the torque converter to go bad and heat up like that with no real noticable side effects? i mentioned my concern about the TC but they didn't seem to ne concerned themselves about it

SOOooooo Does anyone know of a better size to get for a cooler? I haven't gotten a chance yet to see where i could mount one yet but i see one on ebay that claims to "fit" ha. But mostly i was wondering if there was a specific size range that would make the mounting more practical. I haven't seen any videos of anyone installing one on an infiniti let alone an fx model. I do remember someone on here saying after they installed one their temps stayed around 160 which i assume is more ideal than 190+

[VStar650CL]

A Hayden 512 or 697 will fit just about anything, and you won't need larger unless the car routinely tows or mountain climbs. The cheaper 512 is only a good choice if you live in a consistently warm climate, it has no H-valve (bypass) to let the transmission warm up in winter temps. The 697 has a built-in valve that cracks at 160F. The 512 is 17x11 with 6 rows in a loop structure, the 697 is 11x7.5 with 17 rows in a radiator structure.

[crankor]

Good to know thanks

[VStar650CL]

[crankor]

I was hoping i didn't have to post on this thread again.... Well, i hadnt driven the car in a few days from having to have a new y pipe adjusted. I got it back together today and i noticed the shifting was being weird. Well on my way home a punched it and the hard shifting came back. Like it bucks going into any gear. it didn't want to shift after 3rd and weirdly if i revved it up to like 3k (slowly since it wasn't shifting higher on it's own) i could pop it into neutral then back into drive and it would shift into the proper gear without the bucking. My question is does this sound like a bad torque converter or something with the valve body? i replacement valve body is only like 200 less than me getting a used transmission vs a new torque converter so trying to figure out the best option. though if i have to replace the TC i may as well just replace the transmission for the labor cost alone of having to remove the transmission anyway

[VStar650CL]

It sounds like something internal is screwing with either the sensors or the line pressure. You should be able to stream both. Nissan ECU's aren't very good at detecting Hall sensors that are lying, only if they go flatline. I'd monitor your input, turbine, and output speeds to make sure the numbers aren't jumping around when it misbehaves. If you don't find anything and the line pressure is steady with pump (input) speed, then a VB might fix it. That's with a caveat that your TC is running hot anyway, so a good used tran-ny and TC might be a better path.

[crankor]

I am going to just end up replacing the transmission but i wanted to ask about the slip difference. I did watch some live data and casual driving it doesn't jump around much (sometimes in the negative a little) but if a let off the gas from a 35-40 speed then the slip drops to -400 range until i give it gas again. i'm not sure whats normal for that. Just wish i knew what exactly was causing the hard shifting, if its the TC or something in the valve body. Feels like the TC is going and may have done damage to the VB during one of those times.