I can't figure this out. Why would an auto. transmission shift and pull fine until it warms up, then go completely away? It's a TH400. Fluid level is good. Vacuum is good. I'm a newbie and don't have a clue. All ideas appreciated.
Trans filter might be dirty and getting pluged after it runs a while had this problem with my t400............
Your going to get a lot of the same answers that you got yesterday on the other thread you did on this same subject. Save yourself the agony and just rebuild it.
Yeah, well, I don't mind getting my hands dirty and have more time than money. Somebody out there has a good suggestion. "Rebuild it" requires no thought. If I'm bothering you just skip my posts.
That's a thought. The truck had been sitting for about three years and I haven't changed the oil and filter since running her a bit since changing the oil, filter, and adding some cleaning fluid to the mix. Thanks for the suggestion.
well you wont know anything until you pull the pan. If its full of debris, time for new oil and fiilter. Might be a bad sealing ring. When things are cold, tolerances are tight. When warm, things expand.
Looks like you got the right answers yesterday. If you have lots of time, buy a book on the TH400 and rip it apart. Rebuild parts aren't too expensive
If I was bothered, I would not have given you time I did - on both of your threads asking the same question. Perhaps people are telling you to rebuild it because they have experience with what your trying to fix. Fix it right the first time so it does not leave you on the side of the road when it counts.
This is what the pump in a TH400 looks like inside. This part sits at the front of the transmission, right behind the torque converter. The torque converter hub fits thru the hole, and it has notches that the two tangs in the gear fit onto. See the bushing below the gear? that is what supports the torque converter hub. As the bushing wears, the converter's weight forces the hub down a bit. The gear also is forced down. The teeth on the inner gear are forced into the crescent, and the ends of the teeth wear. That causes a "leak" in the pump. When the fluid warms up, the viscosity decreases, and the fluid has an eaiser time "leaking" past the worn gear teeth, so it does not make as much pressure as it does when the fluid is cold. That's why the trans works ok when it's cold, but not when it warms up.
I have a tough time accepting the answers given. If it works when cold (or ANY time), the clutches, bands and all other mechanical pieces obviously work. So, the problem is obviously related to pressure. As seals (and everything else made up of molecules) EXPAND when they get hot, a worn or weak seal would get BETTER as it got hotter (to a point). The poster above me has a point that fluid gets thinner when hot, but I've never seen fluid so dirty it caused a trans to work cold and not hot. Therefore, my guess is a plugged transmission cooler, causing the fluid to overheat, or pluggage in a cooler line which is ALSO expanding when hot, starving the trans pickup.
I had an old dodge that did the same thing, I dropped the pan and put in a new filter and drove the **** out of it for years.
The "sitting for 3 years" would tend to point in the direction of hard/brittle rubber seals. BUT, they would soften, and therefore seal better when warm; the opposite of what you describe. There's a byp*** circuit that comes into play if the cooler gets plugged also. I think you're dealing with worn out clutches. Drop the pan, any particles, clumps, or heavy deposits, and it's rebuild time. Butch/56sedandelivery.
Aside from the oil and filter change (which has already been done), and fiddling with sticking valves in the gov, mod, and valve body, there isn't much that you can do without pulling the trans and getting it apart. Although we could spend a few weeks talking about it, I guess.
Thanks Squirrel. I appreciate your effort in educating me. If I have to pull it down I'll look there 1st - or 2nd I ordered a book yesterday but have never done more than change a filter and re-fill a transmission. I'm still hoping to somehow solve the problem without goin' all the way. Maybe it is a pipedream? I guess I'll find out.
I can check the cooler lines real quick - well, after I figure out the procedure. I like your reasoning. Thanks alot!
Find the mainline pressure port and install an oil pressure gauge line. Run the line up to the window (gauge is where you can read it) and note the cold pressures in R, D, 2, and 1, then drive it till it starts to slip and note the pressures again. If pressure goes down significantly then this will tell you if front pump is failing.
I dropped the pan this evening and found the filter clogged with a bunch of fine ****. I used a cleaner with the last filter change but put very few miles and little time on the motor since then. It's hard to believe the mess in the filter and the pan in such little time. I'll put a filter and fluid in her tomorrow - then cross my fingers. I appreciate you guys trin' to help me out. Kenny
Kenny , the stuff in the pan is the clutches that are worn out . All you doing is putting more money in something that need rebuilt ! So why waste your time and money and just get the trans rebuilt and be done with it . You know that trans is going to leave you stranded on a dark road one night in the damn cold pouring rain and your trusty cell phone isn't going to work ! Retro Jim
Jim - I know you're right. I'll end up takin' a wack at rebuilding it - then probably have to hire somebody to fix what I screwed up. I bought the truck about a month ago and got the motor runnin' good. I just want to be able to drive it a little. I'm like a kid with a new toy. And I want to see what else needs to be done to make a decent ride out of it. But yeah, even if it runs, it's only a matter of time. I definately won't take a ride on a cold, rainy night until I know it's right.
You are smart individual. But I would think twice about rebuilding it yourself as the turbos are a little more complicated than most people think. I have rebuilt Ford C4's but they have removable bell housings. The case is easy to get the main parts out. But the 400 trans has bell and case as one piece, therefore most of the parts come out the front. Simply remove the trans and have it rebuilt by a competent shop. Also get a new torque converter while you are at it.
myself,i would head to the boneyard and scoop up a 200r4 and be done with it,sell the 400 [needs a rebuild]and recoop a bit of dough.
Listen to REBEL 1 AND SQUIRREL,i think there dead on.There are a # of ways to go,forget auto buy bell housing,flywheel,clutch,preasure plate,3-4-5-6 speed trany,and a cool shifter.Now clutch pedals,ect,ect,ect.You will save money by listining to rebuild it.Who said that????......good luck....................YG.
It never helps anything to change the fluid & filter in a bad trans.Almost every time you have to change a dirty plugged auto trans filter. Its the clutch linings that have stopped it up. Put a stick in it. Ive never had to pour fluid in a stick shift ******. OldWolf
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