I'm having quite a nuisance of a tranny problem. This all started on the highway - pulling into St. Cloud, I had what felt like a massive parasitic loss coming from the tranny. Downshifted into 2nd and everything was fine. Filled up, put it in drive, and away I went for the next 2 days of perfect shifting. 3 days later it happened again, except since then it hasn't gone away. If I go from a cold, dead stop 3rd will work for a while, then either completely drop to 2nd, or feel like I'm driving through sand until I downshift. When it's warm, it always feel's like I'm bogging through sand when in 3rd, not even a chance at engaging like it's supposed to. Any ideas? Thanks, Ilya
What have you checked so far? How does the fluid look? Level? Is the vacuum modulator line free of kinks or leaks? Take out the governor and make sure the weights and valves are free to move and not gummed up.
So tonight's progress got me thinking. The line to the modulator is metal, with two rubber connectors on each end. All the rubber is good. I pulled out the modulator and tested it - good. Couldn't get a small enough magnet to test the valve. Took the governor out - the weights and valve all move well. Fluid that came out all smelled decent and looked clean. Fluid level was low when I first checked it - took about 2 quarts to get her where she needed to be. Along with the tranny issues, it's also been running like crap. The idle is still low and lopey as ever, but I get some major popping and hesitation - it gets really bad when it's warm. Just incase, I changed the gas filter - the old one looked like new. I rebuilt this carb about 5 months ago, so all should be well. This brings me to a sad conclusion - Could the timing chain have skipped on the highway, causing a lack of vacuum for the modulator to function correctly? If so then why did it the full effects pop up, then dissappear for two days? I've got a 300 mile trip to make tommorow :ball:
If the engine is running poorly, it will affect the transmission, and how it shifts. You need to find out why the engine is not running right. Is the engine stock? When was the last time you tuned it up? How do the plugs look? Do you have a vacuum gauge? What vacuum is it pulling? Without any details, it's hard to diagnose anything. If it pops and hesitates, I would check for a vacuum leak first. The way to test a modulator is with a vacuum pump. If it holds vacuum, it's usually good. If there is any ATF on the vacuum side, it is bad.
Stock 455, rebuilt carb, new plugs, rotor, cap, points and springs 4-5 months ago. I used the advanced technique of sucking on the vacuum modulator and letting it hang off my tongue to test it - it was good. No fluid either. No vacuum gauge where I'm at, that's back home. I'll run to the store tommorow morning and get some carb cleaner to check for vacuum leaks, as well as pulling the plugs. Anything besides the carb and intake gaskets that I should check? Edit: From what I've been reading, could the coil be the culprit?
Sounds like the vacuum modulator is bad since you have constantly been putting more fluid in the box. Check modulator with vacuum pump to see if it holds vacuum. You need to find out where the fluid is going.
If checking the simple stuff doesn't turn anything up, it could also be the 2-3 accumulator, 2-3 shift valve inside the valve body, or a sticking modulator valve. It sounds like it might be a problem with a stuck or partially moving valve because of your "driving through sand" comment. But again, try the easy stuff. Use a vacuum pump to check the modulator/modulator vac line so you can watch for leakdown over time. How is reverse, by the way? Devon
Road test in 2nd gear to see if engine pulls hard if so valve timing ok, I would have to go with trans problemmaybe in the valve body .
I don't know what your problem is, but the standard "fix all" for a turb 400 is: 1. check your fluid. If it is burned you need a rebuild. If it is not: 2. Remove the governer, clean it. clean out the cavity it goes into. Remove the modulator, clean it, make sure there are no burs on it, do the same on the cavity. Reinstall, check vavcuum line. That is it, on a Turbo 400 that little procedure has worked for me every time for me as long as the fluid wasn't burned.
Reverse is just fine. The plugs look great. I'm going to pick up a vacuum guage tonight. I know a bad coil could cause stumbling, but could it also cause it to pop?
No vacuum leak, but I did figure out what it was. Pretty much the only thing I hadn't gone over so far was the coil - and when I pulled it out, it had cracked along the + post, and had lost oil. A new coil later, and I have yet to get any stumbling whatsoever. I'm pretty sure that it's good to go in the engine department. Replaced the master while I was at it. The pedal was mush and the rears would lock up, so $16 I now have my solid pedal back. I did remove and clean the governor, all moved as it was supposed to, as well as making sure no fluid was in the vacuum modulator. The fluid does not smell burnt. Which brings us back to where we started. Reverse is great, first pulls as it should, fine into 2nd, then terrible boggyness into 3rd. I'm pulling 15 psi at idle, 20 blipping the throttle.
Sounds like valve body issues now. Or slow clutch apply into 3rd. Could also be 2nd is not disengaging soon enough, don't recall how 2nd is done, think a clutch pak, which might be sluggish on release.
The strange thing is that this started when I was on the highway, cruising at 80. How would that factor into the equation?
maybe the 2-3 shift valve gummed up with metal or clutch material. have you overheated the tranny recently? when was the last time you changed the fluid and filter?:beer
That is exactly what I am afraid of. Don't know about overheating, the tranny temp sensor was supposed to go on this summer. The fluid was supposed to get changed, but plans fell through...and well - this summer. The filter was changed last summer, when I got it running after a 15 year nap.
After 15 years, the valve body probably has some gum in it and you probably have a stuck 2-3 shift valve, probably happened after driving it then slowing down and letting things cool down. The valve body contracts and the valve is probably stuck in the gum. Run some trans medic stuff through it and it might clean the valve body. Let the trans warm up really good, then take it out on the highway and see if it shifts. Do it on a warm day.:Comp:
