MEngineer

Hello all,

I have been working on a 2000 Honda Accord EX, 4 cylinder auto, with some transmission problems, hoping to figure out what the problem is before I give in and have the transmission replaced.

Back story. Car was owned by a single owner until I bought it. Maintenance done at a shop on every interval. New transmissions were installed at 60k and 120k miles by a dealership. At ~188k the transmission start to "slip". Not sure if it's actually the friction plates slipping, the torque converter slipping, or what it was. The car sat for about a year, and that's when I bought it for cheap. The car was owned by family friends, so I'm pretty sure about the history.

I changed the fluid and was able to drive it for a few thousand miles with a couple more ATF changes. Some days the car would drive perfectly, and other days it acted up quite a bit "slipping", not shifting or acting like it was in neutral. Error codes given were P0700, P0740, P0780, and P1750. Usually when acting up clearing the codes by pulling the fuse would make the problems go away and it would drive perfectly for a while.

Now about a month ago D2 and D4 ceased to function all together. Anytime it shifted up higher than first it acted as if it was in neutral. Then it stopped shifting into forward gears at all, but I could drive in reverse as much as I wanted. Pulling the fuse to clear the CEL would give me first back, but no higher gears. The day prior to this it drove perfectly for a 120 mile round trip. That's when I parked it trying to decide what to do. After a couple weeks I got in it to see if anything had changed, which it did. I now had no gears. R-D1 all acted as if it was neutral. No shifting sounds, no movement, no anything in any gear. It park it would lock up and be in park, but in R-D1 it would be free and roll.

Yesterday I decided to go and see what I could do. ATF was on par, maybe a little high. I checked the three sets of solenoids; they all OHM'ed out well and had a solid click when power was applied. I pulled the battery for an hour or so but no change. No CEL from pulling the fuse earlier. Finally after cleaning the solenoids and checking everything when I tried to drive it I had half a reverse gear. I would have to rev it to at least 3,000 RPM for it to barely move. Nothing going forward.

Any ideas, suggestions, or what I could check over would be helpful. I can't convince myself it's bad plates if I can't get it to move at all in any gear or even shift into a gear and make bad noises.

If I've missed any important info, please ask and I will fill it in.

Thanks!

MAD_MIKE

P0700. If there is a AT issue this code will be present, it is non specific.
P0740. Lock-up Control System *D4 does not light*
P0780. Mechanical Problem in Hydraulic System
P1750. Mechanical Problem in Hydraulic System

Investing in a transmission pressure gauge kit would be good to start diagnosing, but if the transmission is making whining/whirring sounds when idling/revving the engine that is most likely from the pump cavitating. That occurs when the sump pickup is clogged with material. There is no sump pan to access the filter, case needs to be opened which requires trans removal.

MEngineer

Thanks for the info. I had looked up the codes before, but it didn't really lead me anywhere with the info they had given.

In reverse and neutral there is a whining noise. I don't think it happens in any of the D gears.

If I pull that transmission to split the case and clean it, what is the likely hood that when I put it back in it will be functional? Is there anything specific I should do when I get in there?

Thanks!

MAD_MIKE

If the filter is impacted with friction material then it is most likely the cause of the non-op. However, this will not fix the root problem. These transmissions had an issue with the pressure regulator valve overshooting and blocking ATF flow below ~1200rpm. This would cause a few issues, biggest one was the torque converter clutch would drag, this would overheat the fluid and dump massive amounts of clutch material into the transmission.
Proper fix is to modify the valve body to allow correct operation of the PRV, Sonnax sells a replacement PRV for this issue.

60K miles was about par for the bad transmissions, Honda replacements were usually just rebuilt to factory specs without the PRV issue addressed so the problem would rear its head. At 188 it's due for another rebuild, this time have the PRV replaced with the Sonnax or equivalent valve to allow the trans to work properly.

MEngineer

I will look into having a used/rebuilt one dropped in then. There are local listings for functional used transmission swapped in for $600. I'll start doing some research. Can the PRV be replaced on a functional one that I have swapped in if it isn't already?

Thanks for the explanation. This is the first place I've read the actual root cause and symptoms.

MAD_MIKE

Valve body is located in the torque converter housing. Case would have to be opened and the gear set removed to gain access to the valve body... to give you an idea where the VB is on the Honda transmissions...
Honda Automotive Parts

#5 is the regulator body, it bolts to the main valve body, which if you note #3 is the Stator that the TC mounts to. PRV is located in the middle of the trans, with no easy access.

If you go that far I would replace the clutches and steels while in there.

MEngineer

I don't think this is something I'm going to try and tackle myself. I don't have easy means to accomplish this. Also for $600 to have a functional transmission dropped in, it's hard to reconcile the time and effort.

If I have a used functional transmission dropped in place, less than 50k miles, are there are precautions I can take to make sure it lasts? Without replacing the PRV?

MAD_MIKE

Nothing really. Make sure the fluid is fresh, verify the cooler is cleared out, verify the switches/solenoids are functional.
FWIW, if you get a JDM trans it will have different solenoid connections compared to the USDM. Use your old solenoids/switches on the JDM trans.

Only way to verify if 'new' trans is OK is to check for flow through the cooler. Not pressure, flow. This is one of the reasons it took a while to figure out what was wrong, there would be adequate pressure shown on the gauges at the various ports, but there was just no actual fluid flow.

Hardest part about cracking the case is removing the large nuts that retain the shafts. Once those are off the main body can be removed and access to the internals is pretty easy.

MEngineer

I'm more worries about time to pull, rebuild, and replace. I'd only have time to work on it during the weekend.

Is there a good source for rebuilt transmissions that isn't insanely expensive, or am I best having a JDM transmission or similar installed? I wouldn't mind doing the straight swap, it's the rebuild I'm worried about doing myself.

MAD_MIKE

Ask around to see if anyone does bench work for reduced cost, but you will have to do the removal/install. Check the shops, if they are organized clean good chance they do quality work. If there is crap, garbage and parts everywhere, not so much. JDM would be the next step. Used US one may be hit/miss.

MEngineer

Thanks for all the help. I'll start looking at my options.

MAD_MIKE

For S&G if you have all the paperwork on the transmission replacements under Honda warranty you may be able to get them to have them look at it for goodwill service. Worst they could say is no.

MEngineer

Unfortunately I don't have any paperwork.

laurab13

Hi, my car is either a 91,92,or 94

I myself am having tranny problems, this am as i was taking my son to school i smelled at burn oil smell through vent while at a stop sign, also while i was driving in D4 the tranny started slipping,but it wasnt shifting too hard,no wind out noise,but the green indicater light turned off than came back on
The car just had an oil change and new filter this summer (5 months ago),maybe it needs new timing belt or tran fluid idk.. i just hope its not a head gasket or tranny gone.. please help
Thank you..

user456101

Just a thought. Honda's are very finicky about the transmission fluid. Always use Honda brand ATF. If you have used something else and are having problems, a quicker, cheaper alternative to try before you pull the transmission may be to try draining (not flushing) and filling several times with Honda brand ATF.