Trans hunting (shift busy-ness) 2-3 light throttle

[TurboBob]

I have had this issue with a couple different cars, several different transmissions, so it seems common.

At light throttle (exact throttle depends on TV adjustment) the trans will shift 2-3-2-3-2-3. Depending on the road grade, it may not stop until I press or release the throttle some.

It would seem that its a common issue, I have seen a few threads on here with this issue. (including one by me).

So far, the only suggestions by several gurus is to tighten my TV. This moves the point at which it occurs, and I can make it happen less often, but it is never fixed this way.

So, has anyone truly fixed this issue? Is it a cross-leak, sticky valve, a design flaw from Hydramatic? Do the MonteCarlo's do it? Would a 2-3 shift spring or valve fix this?

There was a suggestion to change the Governor weight or spring and tighten the TV, but I think this is just a "tune it out" solution, as opposed to a fix.

So, any other info or solutions guys?

Thanks!

Bob

 

[mikestertwo]

I have never seen this problem on a bone stock unmodified (in any way) transmission. The problem seems to arise after things have been changed like pump mods, valvebody mods, spacer plate mods, servo mods. I think what has happen is we have changed the hydraulic calibrations in the system from what was intended. I have noticed this problem really gets exaggerated when you go dual feed. Most likely what is happening is there is a momentary pressure drop on the line controlling the shift valves during the 2-3 upshift (and most likely on all the shifts but it seems the 2-3 shift valve is most affected) which causes the down shift. I don't know that there is a "fix" for this problem but changing the primary governor weight on 2 transmissions that I had did make the problem go away (so far) .

 

[TurboBob]

In someones shift kit (Big box Art Carr, or No-YoYo, I don't remember) years ago, there was a 2-3 shift valve spring change, I wonder if it was for this.

I would think creating a larger difference between the min tv 2-3 upshift speed and downshift speed would help. Perhaps a 2-3 shift valve and bushing from another application.

B

 

[TurboBob]

What are the details of the governor change.

B

 

[turbo nasty]

Does the car shift 2-3 ok at WOT??

 

[mikestertwo]

What are the details of the governor change.

B

I increased the primary weight by 2.5 gms. then adjusted the T.V. cable one "click" at a time until I found a sweet spot where it worked. My shift points at light throttle were just slightly lower (about 1-2 mph) with no noticable change at WOT.

 

[mikestertwo]

In someones shift kit (Big box Art Carr, or No-YoYo, I don't remember) years ago, there was a 2-3 shift valve spring change, I wonder if it was for this.

I would think creating a larger difference between the min tv 2-3 upshift speed and downshift speed would help. Perhaps a 2-3 shift valve and bushing from another application.

B

The different 2-3 shift valve spring was in the Art Carr kit. I remember installing one years ago but I think I took it back out in a pretty short period of time because it raised the light throttle 2-3 shift point too much.

We are on the same page with possibly changing the 2-3 shift valve and sleeve with a different model. I had thought about that but never tried it. Too many other projects.

 

[TurboDave]

I have had this issue with a couple different cars, several different transmissions, so it seems common.

At light throttle (exact throttle depends on TV adjustment) the trans will shift 2-3-2-3-2-3. Depending on the road grade, it may not stop until I press or release the throttle some.

It would seem that its a common issue, I have seen a few threads on here with this issue. (including one by me).

So far, the only suggestions by several gurus is to tighten my TV. This moves the point at which it occurs, and I can make it happen less often, but it is never fixed this way.

So, has anyone truly fixed this issue? Is it a cross-leak, sticky valve, a design flaw from Hydramatic? Do the MonteCarlo's do it? Would a 2-3 shift spring or valve fix this?

There was a suggestion to change the Governor weight or spring and tighten the TV, but I think this is just a "tune it out" solution, as opposed to a fix.

So, any other info or solutions guys?

Thanks!

Bob

Are you sure it's the 2-3 and not the 1-2? My 87 does it under very light throttle and moving pretty slowly, on occasions. But mine bounces between 1-2-1-2-1-2, letting off the throttle or pushing into it a little more will clear it up. I wish I could remember what shift kit was installed in mine.

 

[mikestertwo]

Are you sure it's the 2-3 and not the 1-2? My 87 does it under very light throttle and moving pretty slowly, on occasions. But mine bounces between 1-2-1-2-1-2, letting off the throttle or pushing into it a little more will clear it up. I wish I could remember what shift kit was installed in mine.

In my case, it's definitley the 2-3 shift. On a dual feed trans it's very noticable and can get quite violent. I made a mod to the direct clutch to get rid of the abusive 2-3 shift but that's another story.

 

[TurboDave]

In my case, it's definitley the 2-3 shift. On a dual feed trans it's very noticable and can get quite violent. I made a mod to the direct clutch to get rid of the abusive 2-3 shift but that's another story.

I could be mistaken, maybe I better dust off the 87 and take it out a few more times to make sure what gears I'm talking about.

 

[TurboBob]

I have been reading over some of the tech documentation, and wanted to post more questions, and info.

It looks like that 2-3 spring would probably raise the shift point some, and perhaps at a higher RPM the governor pressure would be more stable and the hunting would be less likely.

But it seems that the hysteresis in the shift points (difference in the upshift speed and downshift speed at min throttle) is more a function of the valve geometry that that spring.

So, who has data on the different 2-3 shift valves and springs available?

Anyone have a few lying around they can measure?

How about min throttle shift speeds for 2-3 and 3-2 for the various flavors of trans. (BR, CZ, ....) Perhaps in relation to governor calibrations.

Any other information about solving this issue? It seems more common than I thought, and a good solid fix would be good for the community as a whole.

Thanks!

Bob

 

[brian]

Bob,
After doing some poking around, and comparing a few things... I tried something using a CZ gov. The CZ governor used a spring on the large weight as well as the small one.
This seems to have squashed the issue. More to come later, once I know for sure.

Brian

 

[HellOnWheels]

I have had this issue with a couple different cars, several different transmissions, so it seems common.

At light throttle (exact throttle depends on TV adjustment) the trans will shift 2-3-2-3-2-3. Depending on the road grade, it may not stop until I press or release the throttle some.

It would seem that its a common issue, I have seen a few threads on here with this issue. (including one by me).

So far, the only suggestions by several gurus is to tighten my TV. This moves the point at which it occurs, and I can make it happen less often, but it is never fixed this way.

So, has anyone truly fixed this issue? Is it a cross-leak, sticky valve, a design flaw from Hydramatic? Do the MonteCarlo's do it? Would a 2-3 shift spring or valve fix this?

There was a suggestion to change the Governor weight or spring and tighten the TV, but I think this is just a "tune it out" solution, as opposed to a fix.

So, any other info or solutions guys?

Thanks!

Bob

Mine did the same thing, turned out the speedometer needle would "bounce" at slower speeds and that would set off the VSS which would drive the ecm nuts, along with the trans shifting....and me.

HTH

 

[TurboBob]

Bob,
After doing some poking around, and comparing a few things... I tried something using a CZ gov. The CZ governor used a spring on the large weight as well as the small one.
This seems to have squashed the issue. More to come later, once I know for sure.

Brian

Any info on this?

Bob

 

[BEATAV8]

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