TH200-4R Accumulators - which is the 1-2?

[jthomas]

On the TH200-4R, the accumulators are on top of each other separated by a plate. Which one is the 1-2 and which one is the 3-4?

Reason I ask:
I've been troubleshooting an intermittent second gear start. I did two things so far since they were easy to get to without pulling the valve body:

1. Replaced the TV sleeve and plunger and made sure the TV valve was set right for each position. I have the Bowler TruShift system which corrects the geometry when using a carb and the TV travel checks out fine. The most common cause of second gear starts is too much TV pressure (over 90 or so). I'm good there. I'm at 75 at idle TV. My pressure gauge and shift patterns confirm my TV is set right. Shifts are firm, no flares, no early or late shifts. Shifts into all gears, downshifts are clean and at appropriate times and I can do all of these shifts without issue: 1-2, 2-3, 3-4, 4-3, 4-2, 3-2 and 3-1, BUT, I can't always get 2-1 when I come to a stop. It usually does go to 1, but sometimes it doesn't, especially after warm-up. Bottom line, the Sonnax TV sleeve and plunge did not fix the issue and everything remained as it was with the old sleeve and plunger.

2. Next, I cleaned the Governor and pressure tested to be sure it wasn't leaking governor pressure to other circuits at the wrong time. No leaks. Didn't expect that to fix it and was right. Did not fix the issue.

I have read that after making sure the TV system is not the cause of a second gear start, the next test is to put the selector in Neutral and back to overdrive and also try 1st and back to overdrive.

• If putting it in neutral and back to OD resolves the second gear start it is likely to be a stuck 1-2 shift valve, or too much governor pressure on circuit.
• If putting it in neutral does not fix it, the try putting it in 1st gear and back to OD. If that fixes it is is likely to be an accumulator cross leak.

Mine ONLY resolves if I shift to first gear. It does NOT resolve if I shift to neutral, so the article suggested a cross leak in the accumulator is my next logical test.

Based on the above, IF the 1-2 accumulator is the one I can get to without pulling the valve body, I will get the pin and reamer kit and a new piston seal and try that next.

I may just hold off because I plan to send the tranny to Dave Husek for a full rebuild this winter. Although it's working good, I am getting thrust washer material in the filter at every change and it is increasing so its on its way to trouble, but I still have a little time to drive it yet and wanted to see if I could fix the 1-2 for now.

Thoughts on my plan...right/wrong?

 

[TexasT]

Do you have a gauge on it so you can see it when driving? I tape the gauge to the windshield. Is this second gear start after it warms up you come to a stop sign and see the pressure return to 75psi? I'm more apt to think the tv valve Is getting stuck and when you pull the shifter to 1 it pulls the trans to first. I put a small spring at the bottom of the tv valve to make it return to base as I didn't like how the valve worked on the bench. It seemed sticky so i put the spring in there.

To answer the question you will have to pull the stuff as the 1-2 is in the trans.

 

[jthomas]

Do you have a gauge on it so you can see it when driving? I tape the gauge to the windshield. Is this second gear start after it warms up you come to a stop sign and see the pressure return to 75psi? I'm more apt to think the tv valve Is getting stuck and when you pull the shifter to 1 it pulls the trans to first. I put a small spring at the bottom of the tv valve to make it return to base as I didn't like how the valve worked on the bench. It seemed sticky so i put the spring in there.

To answer the question you will have to pull the stuff as the 1-2 is in the trans.

Thanks TexasT. Yeah, I have the gauge mounted in the dash. It returns to 75 as soon as I let off the gas even when I am getting the second gear starts. In an earlier post (a few months ago) I mentioned it was sticking at 110 when that happened but it turned out my gauge line was pinched and causing erratic readings. I since put in an AN line to the gauges and now I am getting correct readings. Not saying the TV isn't the cause...you may be right, but the pressure gauge sure doesn't suggest that is the issue. I saw the thread about the TV spring lineup and I even bought one of those anti-stick conical springs used in the 700R4 and the smaller spring at the end of the TV valve, but I didn't want to try to drop the valve body from under the car to install it. I can fix just about anything but pulling the valve body scares me a bit. I'm afraid of stuff dropping out and not knowing where to put it back in...

As for the 1-2...it figures it is the one underneath.

So if I decide to pull the valve body to take a deepr look at the TV line up and the 1-2 accumulator:

• Can I do it from underneath the car without stuff falling out?
• I assume I have to replace the VB gasket?
• Are all VB gaskets the same for this tranny or are there variants?

 

[TexasT]

Stuff is gonna fall out. You will need some trans gel or vaseline to keep them in place when you put it back. I'm kinda a hack and used springs I got at my local hard ware that as closely matched or were stiffer if that is what I was after.


I was told in a post by Lonnie D to use a 2.1" spring in the tv valve. So I went to the hardware and bought some that were similar and I cut it to have it be 2.1".


You can see to the left there the size spring I used as a return . I tried several, even one of those cone ones but this one seemed to work best on the bench so that is what I used.




It isn't as hard as it seems but it is messy. Take your time. PM me if you want.

Upon looking at the notes and pix the 1-2 is the bottom with the cover. I put a white spring in and was told to space it out 1/4" so I put a nut in there. I know, redneck but hey, worked for me. Just don't try to pull the cover down with the fasteners as it will pull the threads out of the trans case.

 

[jthomas]

Wow, thanks for the check ball diagrams. It's so odd, because I took it out tonight for a long ride after posting this and not a single second gear start. Ran great. Was warm out too. Now tomorrow night if I take it for a ride it could start again. It must be something that's just on the verge of being off. I guess I should pull the valve body and see exactly what the TV lineup looks like from inside. When I had the TV sleeve and plunger out I measured the spring. It was 2.09". I know stock is 1.9". And If I recall correctly the Sonnax Spring is 2.09". But I also know some of the HP builders use 2.1" like you said. You may be right about the TV setup. The only way to know for sure is to pull the valve body and bench check the lineup like you did. Might just be sticky and not quite returning to full return position, but I would think that would show on the gauge. Baffling...

 

[INEEDAGN]

The 1-2 accumulator is the one that can be pulled without removing the valve body.

 

[jthomas]

Okay...cool. You both confirmed the 1-2 is the one I can get to without pulling the valve body. So, can anyone tell me the functions of the 1-2 accumulator? What does it do and when does it do it. It may be that the spring I have in there is stock and I need a different spring. When I pulled it this past week to clean and check it, It was not a strong spring for sure. The tranny works so well right now aside from the intermittent second gear start that I don't want to start swpping parts without being sure I am selecting the right stuff.

Could this second gear start be as simply as a small cross leak in the 1-2 accumulator or a weak 1-2 accumulator spring?

 

[jthomas]

So I've been studying the principles of operations and learned the 1-2 accumulator controls shift firmness. It doesn't affect shift points. My 1-2 upshift is right where I want it...firm at medium throttle and very firm at WOT. The 1-2 downshift is also good just like it is, except of course when it doesn't go to first occasionally on a stop.

So I don't think I want to make a spring change...its good where it is. Unless the spring has some effect on preventing the 1-2 downshift when coming to a stop...I don't think it does, right?

If the above assumptions are right, I should leave the spring alone and take steps to be sure I don't have a cross leak from accumulator pin or piston seal wear. In my mind, that means the next step would be to replace the accumulator piston and seal or use the old piston, new seal and use the Sonnax oversize pin and reamer kit to recondition it and eliminate any leaking by the pin. These steps should ensure no cross leak and should fix the intermittent second gear starts, assuming the issue isn't in the 1-2 shift valve or the TV line up. Sound right?

If the above doesn't solve the problem, then the valve body comes down and I look at the TV line-up again and verify the 1-2 valve isn't sticking.

Tell me where my thinking is right or wrong...