904 Valve Body

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bobscuda67

bobscuda67

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So I took my car out of storage today and went to the gas station for fresh fuel. Coming home I pushed it to about half throttle and let it shift itself.
The 1-2 shift was good and quick, but the 2-3 shift flared like it always has.
It's a 904 with a Trans Go TF-2 kit in it.
This thing has been the pain in my neck for the last 5 years.
I've had it in and out of the car 4 or 5 times now replacing seals and checking clearences. I've had two different valve bodies in it. Adjusted the bands many times, throttle rod too.
Would a aftermarket valve body quicken the 2-3 shift over a stock valve body with a TF-2 kit in it? Would it increase the pressure over a TF-2 kit?
I wouldn't mind spending the money on a new valve body if it would fix it.
But the way my luck is I'd spend the 250 and it won't make a difference.
 
I'm no expert but this could have many other causes than the valve body. A bad seal on the 2-3 clutch apply piston? Worn clutch plates? Worn band? Weak 2-3 solenoid?

Me thinks you'll have to tear it down to find out. You seem to have all but eliminated the valve body as the source of the problem.
 
64ValiantConv said:
I'm no expert but this could have many other causes than the valve body. A bad seal on the 2-3 clutch apply piston? Worn clutch plates? Worn band? Weak 2-3 solenoid?

Me thinks you'll have to tear it down to find out. You seem to have all but eliminated the valve body as the source of the problem.
Click to expand...

Thanks for the ideas but this trans is all brand new inside as it has been gone thru and seals replaced four times in the last five years. Thats the frustrating part.
 
During rebuild, when installing the 2-3 (or the 1-2) clutch apply piston, it's a bugger trying to get the piston into the cylinder, and very easy to maul or turn the lip on the seal. Bad seal = poor/slow clutch engagement. Just a thought.
 

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A couple of common problems I've read about are the low/reverse servo getting cocked in the bore (there's a problem solver super servo for $39 that fixes this), and cracked clutch apply pistons. Both problems are easy to overlook during a rebuild.

I believe the low/reverse servo problem can cause many different problems, the 2-3 flare being one of them. A cracked/leaking 2-3 piston can definitely cause this problem.
 
Did you install the cup plug into the correct oriface in the case? And drill the cup?

Which is part of the TF-2 kit...

If he has reverse then the rear servo is working fine.....the rear servo kit is available for about 15 dollars from sonnex..
 
64ValiantConv said:
During rebuild, when installing the 2-3 (or the 1-2) clutch apply piston, it's a bugger trying to get the piston into the cylinder, and very easy to maul or turn the lip on the seal. Bad seal = poor/slow clutch engagement. Just a thought.
Click to expand...

Last year I had the trans out again and took the direct drum apart and it had a rolled inner piston lip seal. I had that fixed, I don't have a piston compressor, at a trans shop and put it back together. It shifted better, but not like it should.
 
70aarcuda said:
Did you install the cup plug into the correct oriface in the case? And drill the cup?

Which is part of the TF-2 kit...

If he has reverse then the rear servo is working fine.....the rear servo kit is available for about 15 dollars from sonnex..
Click to expand...

Hey Tony, I did not install the cup plug that came with the kit. I thought that was for eliminating a overlap problem.
 
The odd thing about the way it shifts is that the 2-3 shift is fine at low speeds and the 2-3 and 2-3 shift at wot is perfect. But at half throttle it has a flare on the 2-3 shift, 1-2 shift is quick as it should be.

I took the valve body out last night and started checking the kit install I did.
What I'm thinking is the cam on the TV is not pushing fast enough. I have the TV fully compressed at wot but it doesn't touch it at idle. I have a Edelbrock carb and their throttle extension. Maybe the ratio for moving the TV linkage is to slow. I have another post trying to find out the length of the Miller measuring tool used to set the cam stop.
Thanks for your help guys.
 
bobscuda67 said:
Last year I had the trans out again and took the direct drum apart and it had a rolled inner piston lip seal. I had that fixed, I don't have a piston compressor, at a trans shop and put it back together. It shifted better, but not like it should.
Click to expand...

That's an interesting comment, got me thinking. If you are talking about the 'inner seal', the smaller one that goes on the inner hub (2" or so diameter), the lip on that seal is supposed to be facing downward. I can't visualize how that seal could get rolled while installing the piston unless the seal is installed backwards with the lip facing up.
 
...............The measurement for the tp is set with the gauge that comes in ur trans go kit......how many turns do u have the line pressure set at?..what r ur bands set at?......what ratio lever is in there?.........kim.........
 
64ValiantConv said:
That's an interesting comment, got me thinking. If you are talking about the 'inner seal', the smaller one that goes on the inner hub (2" or so diameter), the lip on that seal is supposed to be facing downward. I can't visualize how that seal could get rolled while installing the piston unless the seal is installed backwards with the lip facing up.
Click to expand...

When I took it apart there was a section of the seal, about 3/4's of an inch long that was fliped over. I had a trans shop install a new seal and reassemble the piston in the drum. They air tested it with the input shaft and pump, it was good to go.
I think the first shop that rebuilt it did have it flipped when they put it together.
 
oldkimmer said:
...............The measurement for the tp is set with the gauge that comes in ur trans go kit......how many turns do u have the line pressure set at?..what r ur bands set at?......what ratio lever is in there?.........kim.........
Click to expand...

Hey Kim, I did not see a gauge for the tv valve adjustment. I have it set at an 1/8 inch between the cam and the valve at rest.
Line pressure is set at two turns from flush. Front band is 1 1/2 turns and rear is 3 turns. It has a 4.2 lever, five Red Eagles in a four clutch direct drum and four in the rear drum. Clutch setting are .070 in the direct and .023 in the rear drum. Also has the accumulator blocked off and the rear servo has the Trans Go spring in it.
 
bobscuda67 said:
The odd thing about the way it shifts is that the 2-3 shift is fine at low speeds and the 2-3 and 2-3 shift at wot is perfect. But at half throttle it has a flare on the 2-3 shift, 1-2 shift is quick as it should be.

I took the valve body out last night and started checking the kit install I did.
What I'm thinking is the cam on the TV is not pushing fast enough. I have the TV fully compressed at wot but it doesn't touch it at idle. I have a Edelbrock carb and their throttle extension. Maybe the ratio for moving the TV linkage is to slow. I have another post trying to find out the length of the Miller measuring tool used to set the cam stop.
Thanks for your help guys.
Click to expand...

TP shouldn't cause a flare. Also there needs to be some clearance between the TP lever & the valve. It's unlikely its worn that much or not moving it fast enough. You would have to be constantly in & out of it all the time to wear it down that bad.
My 727 had a similar problem the 1st time I did it back in High School & we found it had a leaking kick-down servo. I learned alot more about trans overhauls since then.:banghead::violent1:
Do the shift valves (& all the valves) in the vavle body move freely in their bores?
It could still be a front clutch piston seal too. I know you had it done over before but it may have failed again. That's usually the most common cause of a flare. Also check the fit between the shaft & the drum & also the alignment of the feed holes. Any excessive clearance or misalignment will cause problems.
 
The shift valves are burr free and move freely in their bores.
The trans shifts perfectly at slow speed and wot. If the drum seals were leaking wouldn't it be worse at wot? I had the pump clamped in a soft jaw vice with the input shaft and direct drum installed in it. I poured trans fluid in the clutch drum and applied 35 psi of air to the pump and there were very few bubbles in the fluid. It's sealed tight.

I read online that someone was having the same issue as me with ther TF-2 kit, and they called the Transgo tech line. Their answer was that the tp valve in the valve body was to short. How can that be?
I'll call them Monday and see what they say.
 
So I called the TransGo tech today and he said to put a gauge on the accumulator port and with the car on jackstands, put it in drive and move the kickdown rod towards the firewall slowly. When the pressure starts to rise, mark that point somewhere on the linkage and the trans.
Thats where carb stud and the backside of the slotted kickdown adjuster go together.
The problem now is the trans kickdown stops the throttle from achiving wot.
How can I fix the linkage? Making it longer won't do it.
Thanks for any help.
 
.....................when u blocked the acc did u put a blocker under the acc between the case or between the vb and acc.........turn up ur line pressure 2 more turns.......i hope ur not confusing flare up with bind up....i have never not used the cupped plug ..kim......
 
oldkimmer said:
.....................when u blocked the acc did u put a blocker under the acc between the case or between the vb and acc.........turn up ur line pressure 2 more turns.......i hope ur not confusing flare up with bind up....i have never not used the cupped plug ..kim......
Click to expand...

Hey Kim, I do have a blocker rod in the accumulator. The TF-2 kit instructions say not to use the cupped restrictor in a 904. I think I might have to go to a cable kickdown because my throttle has to move about 3/4" before the TV valve starts to raise the pressure. The tech from TransGo told me the pressure should rise in sync with the throttle. Thanks, Kim
 
............With that much play in the linkage u will need to do something to get it out, a cable seems like a good choice.......kim......
 
Here is an update to my problrm.
I bought a Edelbrock extension for the middle linkage. It put the cam on the TV valve in the valvebody like it's supposed to. It's setup so it has a pressure increase off idle and at full throttle it's pushed all the way back.
The 1-2 shift was firmer than before, but the 2-3 shift still has a flare, it didn't dhange at all. I've tried everything and it doesn't make a difference.
I am convinced that this trans will never shift right so I'm either going to get a new 904 or start looking for a manual trans.
 
before trashing the trans it has to come out any way pull the front drum and inspect where the steel rings run in the drum and the grooves in the stator support. these trans will tolerate very little wear in these 2 places.
 
jughead said:
before trashing the trans it has to come out any way pull the front drum and inspect where the steel rings run in the drum and the grooves in the stator support. these trans will tolerate very little wear in these 2 places.
Click to expand...

Thanks for the tip. I'm going to pressure test it while I'm driving to see if anything looks odd before I pull it out.
 
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