904 shift points

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mbaird

mbaird

mbaird
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Trying to get my 904 to shift properly .
1-2 will change with kickdown adjustment but 2-3 seems soft and early no matter what I do.

advice ?
 
mbaird said:
Trying to get my 904 to shift properly .
1-2 will change with kickdown adjustment but 2-3 seems soft and early no matter what I do.

advice ?
Click to expand...

2-3 shifts on stock torqueflights are always a bit...mushy. If your tranny is kinda old it might simply be time for a rebuild. The seals and/or clutch discs might be going bad. What you need to do check out fluid pressure before and after the shift. If the pressure is low it's possible to up the line pressure to improve the shift. But that might only be a bandaid if its rebuild time.
 
trany was just rebuilt.
The shop that rebuilt it is owned by a guy that races a 11 sec Duster with a 904 so I assumed he knew what he was doing.... I am starting to rethink that.
 
mbaird said:
trany was just rebuilt.
The shop that rebuilt it is owned by a guy that races a 11 sec Duster with a 904 so I assumed he knew what he was doing.... I am starting to rethink that.
Click to expand...
Was a good shift kit put in?
 
Has. TF -2... Trany seemed better before he rebuilt it. Had some scoring on the drum so he recommended a rebuild... which I am sure it probably needed.
 
I also bought a 5000 rpm governor from A&A and had him install that.
 
mbaird said:
I also bought a 5000 rpm governor from A&A and had him install that.
Click to expand...

If the RPM's that it shifts at are ok and it just shifts lazy, you can drill the separator plate in the valve body to give 3rd more flow volume.
That way it would shift at the same RPM but firmer and quicker.

Then you might have to deal with a 2-3 bind until you get the front band to release faster.
It's doable, but do you happen to know if the accumulator was blocked?
 
TrailBeast said:
If the RPM's that it shifts at are ok and it just shifts lazy, you can drill the separator plate in the valve body to give 3rd more flow volume.
That way it would shift at the same RPM but firmer and quicker.

Then you might have to deal with a 2-3 bind until you get the front band to release faster.
It's doable, but do you happen to know if the accumulator was blocked?
Click to expand...

It shifts lazy and early... If I adjust the kickdown more the 1-2 shift happens too late but 2-3 shift comes in almost right away.
 
AJ/FormS said:
Have you talked to the builder?
Click to expand...
I have... he said it probably the kickdown adjustment .
After monkeying with it for a while with no success I am hoping a simple adjustment of bands etc can address the issue and I wont have to hassle with him. He seems like a nice enough guy but not very enthusiastic about getting this right.
 
You are talking automatic upshifts, so; IMO
I would drop the VB and airtest the second gear servo and the high drum. If they test Ok, then into the VB I would go. I think you need more spring on the second gear shift valve, to fight the higher line pressure. This will keep in second longer and simultaneously delay third.
Adjusting the KD will never correct a basic mis-matched shift sync.
IMO, and on the street,
if the shift-sync is gonna be mismatched,I'd rather have the 1-2 shift a lil earlier compared to the 2-3...... cuz it's just more comfortable for me around town.. If I need it to stay in first a lil longer, well, that's what the shifter is for.

What this means is if you can't find a stiffer spring for the 2-3 shift valve, then put a softer one in the 1-2....... and readjust the KD to bring them where you want them. If this makes the shift too crisp, then back off the line pressure a tad and work the KD again.
BE prepared to do this several times until you get it right for you.
To make it easier I drilled and tapped the case in line with the line-pressure adjuster, for a pipe plug. Line-pressure adjustments are now easy and fast.
While the VB is off, check the Second gear band apply lever for ratio. It should be in the 4s for performance, else you will slip the band and wreck your drum again
 
Last edited:
Good info ! I like the idea of tapping an access hole for the line pressure adjustment !
 
mbaird said:
Good info ! I like the idea of tapping an access hole for the line pressure adjustment !
Click to expand...

After I typed what I did I saw your complete description on the early 2-3 and have to agree with AJ on the 2-3 shift valve spring. (shuttle valve is the term if I remember correctly.)
You might also run this by the people you got your governor valve from, because I guarantee you they have heard it all before.
 
TrailBeast said:
After I typed what I did I saw your complete description on the early 2-3 and have to agree with AJ on the 2-3 shift valve spring. (shuttle valve is the term if I remember correctly.)
You might also run this by the people you got your governor valve from, because I guarantee you they have heard it all before.
Click to expand...

But why did it shift better before the rebuild ? The TF-2 was already installed .
 
mbaird said:
But why did it shift better before the rebuild ? The TF-2 was already installed .
Click to expand...

IMO either someone screwed up with the sealing rings for the drums or other some such thing like that, or there was a mixup about the new governor.
Unfortunately these are pretty much the two most likely things to go wrong, but even loose valve body to case bolts can cause this so I couldn't even begin to guess what someone else saw or did.

I would definitely contact the governor people before I did anything else to it.
 
The kickdown and the governor will both affect both shifts proportionately. The problem is in the valve body. Who knows what some careless person did. You can try to uncover somebody else's mistake; but it might be wiser, cheaper, and easier to just start off with a different valve body. If you feel up to a learning experience, remove the valve body and start posting pics. I'm sure several readers will spot the problem.
 
CudaFactHackJob said:
The kickdown and the governor will both affect both shifts proportionately. The problem is in the valve body. Who knows what some careless person did. You can try to uncover somebody else's mistake; but it might be wiser, cheaper, and easier to just start off with a different valve body. If you feel up to a learning experience, remove the valve body and start posting pics. I'm sure several readers will spot the problem.
Click to expand...

That is actually a good idea. I have another 904 lined up that I thought I might use as a learning tool for rebuilding.
 
There are a lot of knowledgeable people on here with every type of transmission experience. If you have the patience, you will find more help than you even need; whether you want to just repair the problem, or go thru a tf entirely.
 
I have the Tom Hand book on TFs . Finding time is the issue.... which is why I paid someone to rebuild it in the first place.
 
A lot of the work I get is on trans that have already been rebuilt recently. 9 out of 10 have been rebuilt some time in the past, and I seldom see one that anybody took the time on. Compared to what I've seen, you could slap one together and match the quality control you'll find out there. The end play is almost never addressed, and I almost never find simple upgrades performed. Most just slap a kit in it and go.
 
That sucks! Take it back to the builder and have him fix it because they missed something. With the TF 2 kit in there you should have no problems with lazy shifts.
As long as you have the correct linkage and it's adjusted properly I would guess the valve body is the source of your problems. The 904 is the BVD of automatics and hard to screw up.
 
Did this guy build it himself or did 1 of his flunkies do it? He should of been able to do it in his sleep, so to speak. Or maybe he did and that’s the problem. I would take it back to him to fix. Kim
 
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