Transmission woes

[PotvinGuy]

Sigh...another day working on my back (my wife used to say that before we married, but I never could figure it out). Now get this: the trans moves smoothly thru all 6 gears...with the pan off. I install the pan and it won't go into P. Something about the pan is interfering with the P mechanism. Guess I'll take my 400 book to bed and see what it could be. Any suggestions are most welcome.

 

[T-Test]

If you put the solenoid back in the same place, the pan should go back on if it is the same pan or the detent spring/roller is installed crooked/twisted

Refer to FIRST paragraph..

 

[PotvinGuy]

What solenoid? Pan went back on fine, but the darn trans won't go into P. The shift arm won't move to that position. Something must be blocking it. But it worked fine with the pan off. Making me crazy it is...

 

[Indycars]

Any scrap marks on the inside of the pan? Got a Borescope?

You got to wonder why it worked for so long if something is hitting the pan.

 

[Spanky]

Look real carefully at the linkage mounting points. Has anything become bent, or moved due to wear?

 

[Island Girl]

Not that you haven't gotten plenty of input already, but have you tried holding the pan in place with one hand and shifting the linkage/shift arm and feeling where the pan wants to move away from as it goes into P as a way to locate the offending clearance.?

How about gasket compression taking away the smidge of space it needs to complete the shift, would one of those thick silicone gaskets with the inner steel help?

 

[Gerry]

Come on Dude, you are more intelligent that this. Take a breather an analyse what's going on. It should be a simple thing for a guy like you to solve.

 

[iroct]

Remember if you can't fix it with a hammer it has to be electrical.

 

[T-Test]

[QUOTE="PotvinGuy,

There's a new symptom. The trans has 5 gears, right? P,R,N,D,L. Well, I just found a new one below L! It seems to be another Neutral; nothing moves.

Looking at left side of trans. Now it may be my fault. I did some small mods inside the trans years ago to make the electric shifter faster. Of course as long as it doesn't hurt anything I can just ignore it. But I'll still drop the pan sometime and see what is going on.
And there is new behavior. Now the gears seem to work, at least with the tires off the ground. It's like the trans is possessed. I'll drop it and see if the ?#*@% car moves.[/QUOTE]

Thought there was an internal solenoid moving the shift detent arm. Maybe it is on the outside with a push pull type. But either way I think you have a broken tranny and it needs to be broke open and looked at.

 

[Neshkoro]

It does seem strange that it used to fit with the pan on and now it doesn’t. Could the lever have come loose from the shaft and now is not in the correct position. Maybe that’s the reason you have another neutral past low. I think there is a correlation there. I don’t know anything about automatics, just about mechanical things in general. If it used to work, something changed.

 

[old round fart]

Did you ever find your problem?

 

[PotvinGuy]

I gave up on the Park thing. I don't use it anyway. But there are other problems. 1) Fluid is coming from the vent tube. It's sporadic, but seems to be most active when changing gears. I've rigged a catch can, but don't want to live with that! 2) And the fluid level in the pan seems all wrong. It's near empty when sitting and engine off. But then it jumps up to normal when running. And most perplexing it goes way overfull for a while after the engine is shut off. I can see all this with the sight glass I put on the pan. It doesn't make sense...does it? And yet the tranny seems to work fine, no slow shifts or odd behavior on the road. Could the vent thing be the trans pump leaking? Any ideas on the pan fluid level business? I've called 3 tranny shops, but they won't touch a hot rod. Tomorrow I'll call 2 that supposedly welcome hot rods. At this point I'm thinking I'd just like to replace it with a newly rebuilt unit. After all, I've gotten 25 years use of it and other bits inside it are surely worn. You know the feeling, right, ORF?

 

[old round fart]

I sure do! I tried to rebuild a 700 R4 and didn’t feel good about it so I took it to a trusted shop and he rebuilt it. Said I had so much wrong it would have burned up in 2 minutes. Glad I spent the money just sorry I wasted 2 weeks of a friend’s time trying! My trans rebuild career was very short!

 

[Gerry]

Does that sight glass have a hole in the top to atmosphere?.

Normally when engine is not running the level should be way up the dipstick and then drop to the correct level when running (as the pump refills the TC and system). That's why we always check levels with engine running and car in Park. All trannys will go overfill when switched off due to the above, but they normally stay at that level until the next fire up.

I often wondered how that sight glass worked. If it has a hole in the top to equalise the pressure then fluid would leak out when the engine is turned off. The usual level for fluid when running is just around the sump to case line in 99% of transmission. Normal reason for throwing fluid out of the breather is heat, due to clutched being burnt.

The level in your picture in my opinion is a little low if the engine was running.

Course having worked for 10 years with my buddy in his transmission shop, although not directly involved in rebuilds except for valve bodies and modifications, I should know by now what your problem is. I will ask tomorrow when I go in for a few hours.
Gerry

 

[PotvinGuy]

Thanks, Gerry. Yeah, the sight glass has a small hole in the top and when I shut off the motor, the fluid shoots up and out the hole. And I am using a new sight glass that is much taller:

The black mark on the glass is at the pan level and that is where the fluid is when running...the only part of all this that seems right.
So the level on shut-off is apparently way above the pan. Does that seem right? But then it drops slowly until it is barely showing on the glass! None of this makes any sense to me, but I'm not any kind of tranny expert. Ready to throw in the towel and swap in a newly rebuilt unit.

 

[choppedtop]

Level should rise as Gerry said when engine is off and TC unloads to approx half its capacity.

 

[Gerry]

Well here we go. My bud and I had a 30 minute chat about the possible causes. We enjoy this kind of problem because it gets our brains moving again.

1 get rid of the sight glass and use a dip stick or modify it like I did to the GM350 with a side fill and level plug. Thread on here somewhere about how I did it.
2. On original Ts the sight glass is well know for giving spurious and inaccurate readings.
3 Fluid being thrown out of the breather is normally due to excess heat (Converter or clutches) over full with fluid or something a little unusual; read on.
4. Slip coefficients are not a concern with this trans and the fluid that it uses, so dont worry about the fluid being wrong. Millermatic is the best you can get for this and most other transmissions up to the 8 9 and 10 speeds.

Your electronic selector? You have a problem with Park. The electronics just move the manual select valve to the positions for R N D L2 L1. OK so here's the thing; if your electronics are not engaging the manual select valve in the correct position and on your transmission this is registered inside the gearbox on it own detent, and not on the gear shifter. It would be a good idea to get this sorted out so it works correctly.

If the manual select is not registered correctly then all sorts of bypass and pressure loss can occur. In that case there is a good chance that the clutches are getting reduced pressure and slipping a small amount. You may not feel it but this slip will generate heat and that can throw fluid out of the breather.

The other scenario is if you have overfilled the trans, fluid gets to a level, when it is around the rotating parts (planets clutch drums etc.), which its not meant to be and the parts just stir up the fluid and whisks it like an egg. When its at this high level the fluid becomes air-rated, which increases its level even more and promotes clutch slip and pukes out of the breather.

In a few words use your expertise to do some basic checks and investigations. If the trans is working OK on the shifts ets then chances are is still serviceable. I hate for nay buddy of mine to spend $ when they my not need to.

Hope this helps
Gerry

 

[PotvinGuy]

Thanks for noodling on it. The gear selection thing is really odd. I can move it to P with the pan off, but it won't go there with the pan on! Now P is a bit different than the other gears, since it invokes a long rod that actuates a locking mechanism at the rear of the tranny. Somehow the pan must be interfering with this. The pan hasn't changed, so the problem must be in the tranny, but it all looks fine (and works fine with the pan off).

The spurting from the vent happens as soon as the motor is turned on, so it can't be related to any heating inside the tranny. Could it be caused by a leaking tranny pump?

I'll check the level with the dipstick (motor running and warmed up) and let you know what I see.

 

[fletcherson]

Thanks for noodling on it. The gear selection thing is really odd. I can move it to P with the pan off, but it won't go there with the pan on! Now P is a bit different than the other gears, since it invokes a long rod that actuates a locking mechanism at the rear of the tranny. Somehow the pan must be interfering with this. The pan hasn't changed, so the problem must be in the tranny, but it all looks fine (and works fine with the pan off).

The spurting from the vent happens as soon as the motor is turned on, so it can't be related to any heating inside the tranny. Could it be caused by a leaking tranny pump?

I'll check the level with the dipstick (motor running and warmed up) and let you know what I see.

Have you checked the pump pressure?

 

[PotvinGuy]

Did some testing this morning. Got the motor and tranny warmed up. Watching the sight glass and using it's drain valve, I notice that it takes quite a while to stabilize and show the true level in the pan. This is likely due to the design of the sight glass:

...there is a small passage from the pan to the sight glass. If I drain some fluid with the needle valve on the sight glass, the level in the glass drops quickly. But then when I close the valve the level rebounds and stabilizes. It's a dynamic thing.

Now to the dipstick. It is odd. The dipstick appears to read the same (right at the low end of the range) no matter how much fluid is in the pan. I have no idea what could cause that. And further, when the dipstick is in, the sight glass shows one level, and when the dipstick is removed the sight glass shows a much lower level. It's as if air pressure in the tranny pushes on the pan fluid, making it read higher than true on the sight glass. Then when the dipstick is removed the pressure is relieved and the fluid level in the glass returns to actual. But the tranny is vented, so there shouldn't be any air pressure in it at any time...right? I'm going to take several extra-strength Excedrin and digest these findings.