91 Accord Trans won't shift cold

[woodmanho]

91 Accord, 120K mileage, Auto Trans. Won't shift and stay in first gear when it is cold. It is normal after warm up few minutes. Temperature is about 30F - 50F outside. Please advice, thanks.

[jeffcoslacker]

Clarify for me...it won't upshift, holds in first.... or won't stay in first either, slips to nuetral?

[woodmanho]

Thanks for your reply. It won't upshift, holds in first. The problem will go away after warm up few minutes.

[jeffcoslacker]

OK...I was checking to see if the '91 used a vacuum modulator...I don't find a part number for it but it would be worth asking a dealer. The modulator design uses a vacuum diapragm to signal for upshift...sometimes when the diapragm got holed or the vacuum hose got old and hard they would suck air when cold and leave the tranny stuck in first...you'd have to kinda deliderately overrev and let go of the gas abruptly to get them to upshift until it warmed up.

I guess you already checked the fluid level, right?

Did this happen suddenly, like when the morning temps dropped below a certain point it started doing it? Does it seem to improve a bit on warmer days?

Does this just happen first drive of the day, then fine after?

Notice anything else, like hesitiation to downshift when you need to pass or climb a hill, etc?

[woodmanho]

Thanks for your advice. I try to find the parts and order online, but not seeing any. Is it under transmission catalog? Anyway, I will check with dealer as well?

The fluid is pink and no burn.

It happens constantly first drive of the day in the morning. It will be fine if I just park the car for an hour or two and drive again. However, it will come back again after work when parking all day. Outside temperature is about 30F-50F. I think it is the same even the weather is getting warmer, but I am not sure about summer time. The problem just started this winter, and I will see few months later in the summer.

In the beginning of the problem without warm up the car, it will upshift if I step on the gas all the way down. Now, this trick doesn't work any more.

Thanks again.

[jeffcoslacker]

Originally Posted by woodmanho

In the beginning of the problem without warm up the car, it will upshift if I step on the gas all the way down. Now, this trick doesn't work any more.

This sounds like a pressure bleed when cold...what happens is a seal or o-ring deteriorates and splits or wears in such a way that it can't conform to the sealing surface when cold. The fluid blows off through this point, that's why giving it more gas (increasing the hydraulic pressure) would make it shift initially...now it has deteriorated to the point where the pressure loss is too much to overcome until it softens up. Also a sticking check valve in the valve body can behave this way also sometimes.

If it was a modulator or transhift cable issue, it would not shift when you were pressing the gas, and shift abruptly if you dropped the gas suddenly..so I don't think you need to investigate that any further...

If it was my car, I'd do a fluid change with a quart of KW Transeal or Seafoam added, both work good on old seals and sticky check valves. After a couple hundred miles if there's no improvemnt, it will most likely have to go to a tranny shop for a diagnosis...unless you want to get a good shop manual and drop the valve body and inspect...it's not that difficult, you just have to be damn sure it's right when it goes back together....

The good news is I think the more difficult parts are probably ok...it sounds like a control issue, not worn clutchpacks or something like that.

[woodmanho]

The transmission is running fine now when it is summer now. I am thinking to take the car to the shop to check seal or o-ring before next winter. Is it worthy? Can the shop just replace the seal or o-ring? Does it consider a major rebuild?

On the other hand, I have a 95 Dodge Caravan shift abruptly if I pressing the gas or dropped the gas on 1st gear. It only happens when the car is slowly moving on 1st gear such as traffic jam. Otherwise, the transmission is still very strong. It is a Jasper Transmission. I think I have this issue from Day 1 after the installation few years ago. Any advices!

Thanks in advance.