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No reverse, neutral goes forward, 3,2,1 barely go.. help!?
Hey everyone.
I did some searching for my particular problem, besides taking the tranny apart, was wondering if anyone had an ideas.
So finally got the 77' ready to take a test spin around the block. Car hasn't drove in 20+ years, but tranny/motor rebuilt and installed approx 10 years ago. Car has a 454 with a TH400. Rear end has clean gear oil that comes out when I unscrewed the plug.
I went through my Chilton manual on how to fill tranny, idled the car on level ground, got it warm in park, went through gears, and checked level until fluid was between the two dots on tranny dip stick.
With car on and in neutral, I'm able to roll car out of garage. Start it, put it in reverse, and it rolled back. Gave it some gas in reverse and nothing, it's like it's in neutral. Panicked, I put it in 3rd, nothing, 2nd nothing, 1st I revved and it started to ever so slowly move forward. For how much foot I put in it, it should have been moving forward much faster.
Turn car off, check trans fluid and it was fine. Start it back up, and this time I got some slight forward movement in ALL gears (N,R,3,2,1).
My trans pan has a drain plug on it. I have not tried to drain fluid and replace/take tranny apart.
I got under the car and checked the shifter linkage. The linkage is able to move between gears without issue. I really don't feel alot of movement / rpms changing when I was going through gears.
Just seeing if anyone has some insight or maybe something obvious I am overlooking before getting into something deep!
10 years is a long time for a trans to sit dry. I’d guess that the seals inside have shrunk and hardened, and no longer hold pressure. The trans won’t engage any gear if the internal seals won’t hold fluid pressure.
Agreed, engine running in park.
But also agree. 10 years is a long time to sit dry. And your WAY out of any warranty.
And Chilton manual? Seriously? Get a G.M service manual.
There is a vacuum switch/regulator, forget what it is called, that is on the pass side of the tranny. Some might call it a governor, dang, hate getting old. Could be your problem, easy and cheap to replace....
vacuum modulator. regulates shift points. has nothing to do with this issue. clutch plates could be stuck together. seals shrunk and not holding pressure. first, drop the pan and replace the filter. then new fluid with one of those trans renew additives. it is basically a mild solvent that MAY make seals swell and free up stuck clutch plates. then run it and shift back and forth. let it idle. keep trying to shift gears. it may free up. but don't get your hopes up. if you need a trans rebuild, consider going with an overdrive trans instead. 700r4, 2004r or even a later model 4l60 or 4l80 which will require an aftermarket trans controller, moving mount and shortening drive shaft. but much easier to find in the junkyard...
Last edited by derekderek; 09-19-2022 at 08:27 PM.
vacuum modulator. regulates shift points. has nothing to do with this issue. and the trans is 20 years sitting. not 10. clutch plates could be stuck together. seals shrunk and not holding pressure. first, drop the pan and replace the filter. then new fluid with one of those trans renew additives. it is basically a mild solvent that MAY make seals swell and free up stuck clutch plates. then run it and shift back and forth. let it idle. keep trying to shift gears. it may free up. but don't get your hopes up. if you need a trans rebuild, consider going with an overdrive trans instead. 700r4, 2004r or even a later model 4l60 or 4l80 which will require an aftermarket trans controller, moving mount and shortening drive shaft. but much easier to find in the junkyard...
Thanks, Will be giving this a go. I dont know if this matters, but, I don't think the trans was COMPLETELY dry all this time.
There was some trans fluid at the bottom of the stick when I got to trying to get the car started. I ended up adding approx 4.5 quarts total to get to where it needs to be on the stick. The fluid that had been in there 5-7 years had never been driven and was a nice clean red just like it was fresh out the bottle. I assume the car sitting though would probably still shrink those seals potentially?
I assume the car sitting though would probably still shrink those seals potentially?
Yes, because that fluid is going to pool the bottom of pan. Most of the functional bits (including clutches, drums and seals) will be high and dry above the fluid level. A car sitting a week, a month, several months… the fluid will drain down but parts retain a film and stay, um, moist.
A decade or two? Dry as a bone.
I think the poster with the additive suggestion is on the money. Give that a shot, you really don’t have anything to lose except a few bucks on fluid, filter and gasket.
Car has a 454 with a TH400 .. Unique to the TH400 is the cloth filter. Which will cause the exact issue you describe. Drop the pan and replace it. And don't be surprised if the trans works as it should...
Actually, Vacuum Modulator controls the Pump line pressure to the components, which does have an effect on shift points , On a running engine with the vacuum hose off of the modulator will make the pump run max pump pressure all the time
Hmmm. So, I drained and took off the pan, put new gasket and filter in...... and i collected about 12 pints (1.5 or so gallons) tranny fluid??! That seems like way too much... I added 4 Oz blue devil to the 8 pints I just filled the tranny back up with in case the seals were worn...
too much fluid ? I wonder if maybe the trans dip stick is not the correct stick? The trans pan isnt stock, it is very thick, heavy cast metal with a drain plug.
Will get her off the jack stands and see what it does..
Your standard th400 takes 12 quarts to fill from completely empty.
Pulling the drain plug might drain out about half. Because the TC doesn't drain, pump, cooler lines, and residual.
Actually taking off the radiator line and starting the car for a short period will pump it dry
Right, but just removing the pan shouldn't result in all 12 coming out?
Turned the car on, got it hot, went through p r n 3 2 1 a few times, checked the level with car in park and there was no visible fluid on my trans dip stick at all?
When I let my foot off the brake, the car wants to go forward .... even in reverse and neutral -_- 😵💫😵
Ordered some new gaskets and o-rings, seems like it may be the valve body /reverse servo stuck. Figure I'd put some new gaskets/orings on while fiddling with it. Will let yall know how things go!
Ordered some new gaskets and o-rings, seems like it may be the valve body /reverse servo stuck. Figure I'd put some new gaskets/orings on while fiddling with it. Will let yall know how things go!
If I was going to take the valve body off and this is just me, I would buy a shift kit of a lower level and install the plate
Checked all the linkage, rooster comb, down to parking pawl and all looks good there. Gasket and o-ring kit came in, so looks like I probably need to get valve body off and take a look.
Also, by chance, can any one identify what this may be? When taking off the pan and filter, found this in the bottom of my oil collect pan I drained the trans fluid into?
Looks like a piston or plug in the trans valve body may have fallen out. Many are retained by a steel pin holding which holds it in the VB. Best to get a good description of all the passages in the VB and compare with what you have.
Looks like a piston or plug in the trans valve body may have fallen out. Many are retained by a steel pin holding which holds it in the VB. Best to get a good description of all the passages in the VB and compare with what you have.
Silly me. That piece is a spacer for the bolt that holds the filter in place.
09-18-2022, 09:27 PM
No reverse, neutral goes forward, 3,2,1 barely go.. help!?
