TH400 help.

[83Burban]

So.... I've searched the forum and have not found an answer to this question. maybe I'm searching wrong? Is there a process? Or do you guys just type key words into the search bar like ive been trying?

Regardless....

My trans acts like its low on fluid when its cold. Like....if I just fire the truck up wait for the choke to open and put it in gear, It wont engage unless I get the RPM up. Reverse or drive, does not matter. But....after 5-10min of "warming up" everything seems to function just fine.

Is this normal behavior? Drove it about 20mi down the interstate and then checked it fluid (running and def up to temp) and it shows full. Should I try to add a some Lucas?

Bad pump maybe? Should I be overly concerned? Was hoping to drive it to Colorado next weekend (9 hours)

 

[Vbb199]

Maybe a clogged up filter? Can you hear any whining when you try to put it in gear and it won't go?

 

[DoubleDingo]

If you replace the filter, make sure to get a new one that has the screen, not the dacron. Transmission shops should carry them. I found this out the hard way

 

[83Burban]

Maybe a clogged up filter? Can you hear any whining when you try to put it in gear and it won't go?

No.

Its silent.

Nothing seems out of the ordinary. If I put my foot on the break and gently rev it up....it will engage, and pretty gently.

 

[83Burban]

It feels just like the C6 in my Lincoln would when the oil was WAY low.

But ive checked it a bunch and its not. This truck only has a slight leak on the rear diff. Does not use or lose anything else surprisingly.

 

[Vbb199]

It feels just like the C6 in my Lincoln would when the oil was WAY low.

But ive checked it a bunch and its not. This truck only has a slight leak on the rear diff. Does not use or lose anything else surprisingly.

Dip stick at the correct length??

 

[83Burban]

Dip stick at the correct length??

It appears to be the stock tube and stick. And the tube does not seem to be loose.

 

[83Burban]

I would assume that if it was low on fluid, that it would act that way regardless of temp.

Again, it's only when its cold. Which is odd to me.
I've read that overfilling these a little is no big deal. Can anybody confirm this?

I just drove it 175mi to SE Kansas....zero issues...driving into the wind I was getting 11.5mpg at 65-69mph. Using non-ethanol 91 (timing was set with this fuel)

 

[Vbb199]

I would assume that if it was low on fluid, that it would act that way regardless of temp.

Again, it's only when its cold. Which is odd to me.
I've read that overfilling these a little is no big deal. Can anybody confirm this?

I just drove it 175mi to SE Kansas....zero issues...driving into the wind I was getting 11.5mpg at 65-69mph. Using non-ethanol 91 (timing was set with this fuel)

It should puke out what it doesnt need via the vent up top

 

[JoeR Jr]

Before I dropped the pan on it I would take a pressure check to see wht it looks like in Park and when you drop it into gear. If it's making the proper pressure and still doesn't get drive then you're taking it apart. If it's low on pressure then drop the pan to see if the filter is starving the pump, or maybe sucking air.
Joe

 

[Matt69olds]

Drop the pan, change the filter. Get a filter with a screen (some call it the Allison filter) the cloth filters are pretty restrictive and can cause the concern your having.

If there is a ton of crud in the pan, most likely the filter is partly clogged up. When the fluid is old, the trans can’t pump enough fluid thru the filter to engage the clutches/bands, causing the delayed engagement and whine. Once the engine runs a few minutes and things warm up, the fluid thins out enough that the pump can supply enough fluid.

If the pan is really full of debris, chances are the transmission is nearing the end of its life. If you change the fluid and filter and it shifts firm, and goes immediately into gear, you might have dodged a bullet. I’d run it without too much concern. For the most part, TH400 transmission don’t break, but you might wear one out. Usually the only time wearing one out damages parts is due to lack of lubrication.

 

[Ricko1966]

When you have the pan off put a drain plug in the pan.At oil changes drain the transmission pan too. Its just a few quarts but at the end of the year it's almost a full fluid exchange instead of 70,000 mile 9 year old atf. Just my opinion

 

[mmerlinn]

So.... I've searched the forum and have not found an answer to this question. maybe I'm searching wrong? Is there a process? Or do you guys just type key words into the search bar like ive been trying?

Regardless....

My trans acts like its low on fluid when its cold. Like....if I just fire the truck up wait for the choke to open and put it in gear, It wont engage unless I get the RPM up. Reverse or drive, does not matter. But....after 5-10min of "warming up" everything seems to function just fine.

Is this normal behavior? Drove it about 20mi down the interstate and then checked it fluid (running and def up to temp) and it shows full. Should I try to add a some Lucas?

Bad pump maybe? Should I be overly concerned? Was hoping to drive it to Colorado next weekend (9 hours)

Sounds like a case of morning sickness to me.

Morning sickness is caused by fluid draining out of the converter back into the transmission when sitting overnight. The next morning, the transmission will not engage until the converter has been pumped full of fluid.

Not sure of the cause, but does not seem to be a big issue IF the motor is NOT revved up IN GEAR before the converter refills.

 

[SquareRoot]

Mine used to do that. Swapped in a NV4500 and it fixed it and ....I gained 25% mpg. weird

 

[Matt69olds]

Morning sickness is a possibility, but I’m assuming the OP is having the concern after sitting overnight. It takes a lot longer than a few hours to drain the converter.