wierd TH400 activity

[magnethead]

should an automatic ever shift out of first gear at 10 MPH with 4.10 axle gears?

when i kick my truck off high idle, it idles in park at 1400, I put it in gear, and it shifts to second gear before the end of the driveway without my foot on the pedal, and when manually downshifting, it won't go into first unless i'm under 10 MPH.

Also, it seems to spool up way high (like the 2500+ range) in first gear under launch if i make it hold the gear yet it barely makes it to 15 MPH. By my math, that would have to be a ton of slippage in the convertor or a 5 something first gear (TH400).

BTW, it does have a RV shift kit.

[Prerunner1982]

This probably has nothing to do with it, what does your truck idle at normally? 1400rpm? If so, bring that bad boy down a bit. My 82 idled at 800-900 RPM in Park.

[krazymonkeys24]

Check your modulator valve. i had one do something similar once. the difference was that it wouldn't downshift at all, even with the kickdown cable. Hope this helps.

[magnethead]

when I kick it off high idle, it idles (bounces) between 12 and 1400 RPM. After it's warmed up (1/4 way on gauge) it idles in the 6 or 700s.

I checked it again by making it hold first gear, and it was 2000 RPM at 15 MPH, which actually calculates out correctly, but the engine sounded different (higher pitch) than it does idling at 2000 on high idle. Not just under load louder, more like jet car louder. Almost sounds like turbo whine.

Something i hadn't thought of before- when it shifts from second to third, it lugs along until it gets back to 1800 RPM. Sometimes i'll make it go back to second and hold it longer because it sounds like it wants to die. And going up a steep grade here, It doesn't downshift, even if i try to nake it kick down. I'll get down to 1000 RPM and keep dropping and lugging, then i'll force it to second and it'll spool up and climb up fine. In gear, it idles in the 500 RPM range. It just seems to really like third gear, and i've figured out that downshifting an automatic while moving isn't fun, nomatter how much I try to RPM match the gears.

Something else- when I shift it into gear, lately it's been lunging whenever it goes in gear, like shifting a manual with the clutch only halfway in, in both forward and reverse. It's basically a clunk sound as it falls into gear. Trans fluid is full, and i've never noticed a shock, and surely a 454 doesn't have enough torque at idle to do that? Although recently, just to see, i've had the e-brake 3/4 way down and brought the RPM up during the shift from reverse to drive, and i'll spin the right rear tires. Either my right sides aren't on the e-brake cable, or it has more torque just off idle than it does at 2800 RPM (supposed torque peak).

is that 0.48:1 difference between second and third gear really that ig of a drop to cause the motor to lug?

[MylilBowTie]

My th400 does the same type stuff. It will shift into 3rd under 20 mph sometimes. It lugs down the engine but it powers through it. 3.08 gears and 30in tires add more to the lugging. It has to barley be idling or very light throttle to get it to shift by itself into 3rd like that. Mine seems to not like 2nd gear very much. It doesn't hold second for very long, doesn't downshift to second ever, doesn't have any manual braking. But it will bang second gear with a chirp or scratch from the tire @ WOT.

I think my convertor isn't all up to what it used to be either. Doesn't seem to apply the power to the rear like it used to before. I've had problems out of it and I don't think all the fins are still intact. Its done that type of thing twice now. Both times it got really loud like a bottom end knock kind of sound. Its always fixed it self but I've had to take it real easy on it when it did that. It never has slipped at all and it goes into all the gears positively. I have gotten really lucky with it or my truck really loves me somehow. I do have another backup th400 at the ready if it does quit. I'm running an external transmission filter / cooler and transgo shift kit.

[krue]

There's an article in the Car Craft I got yesterday on the TH400, maybe some info that would apply to y'all?