Missing 3rd on 904 trans

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BodyBag

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Background: Did a 5.9 magnum/ 904 trans swap on my 66 valiant. Both were used and the trans never had 3rd gear. I ended up doing a garage rebuild on the transmission and the 3rd/reverse clutches were definitely toast(pic of one of the clutches included). While I had everything out I installed a B&M Z gate shifter. I'm still missing a gear. Reverse works fine but from a stop manually shifting from 1-2 does nothing and 2-D shifts to second. I thought I had the linkage off by a gear but shifting to neutral and it goes to neutral. The car has 3.55 gears in it and I was running about 4000 rpm doing 65-70 on the freeway on the way to work(same rpm's it would turn at that speed before the rebuild).

Any ideas on what to check out adjust would be greatly appreciated.

20230114_104844.jpg
 
Did all the valves move freely in the valve body?
Did you take apart the valve body?
Are all the check balls in the correct location?
 
All the valves moved freely and other than the fried clutch plates I didn't notice any damage or wear. Unfortunately since I found the clutch plates were toast, I didn't want to tempt fate and take apart the valve body and risk losing parts or putting the thing back together incorrectly.

The more I think about it the more sure I am the first time or two I drove it after the rebuild I had all 3 gears. After the this first couple drives I had to park it to deal with some other issues and just got those squared away this past weekend.
 
I was hoping it was going to be a 3rd/reverse band adjustment or linkage adjustment from the new shifter. Hopefully tomorrow I'll have a chance to jack it up and see what I can find.
 
BodyBag said:
I was hoping it was going to be a 3rd/reverse band adjustment or linkage adjustment from the new shifter. Hopefully tomorrow I'll have a chance to jack it up and see what I can find.
Click to expand...

The troubleshooting chart in the Motors.Manual or TSM is a great reference.

I hope it's simple.
 
BodyBag said:
I was hoping it was going to be a 3rd/reverse band adjustment or linkage adjustment from the new shifter. Hopefully tomorrow I'll have a chance to jack it up and see what I can find.
Click to expand...
There is no 3rd/reverse band, only manual low/reverse band.
 
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How is reverse? No bands are applied in 3rd... The front & rear clutches are applied...
The rear clutch is applied in 1st. 2nd & 3rd... So that isn't the problem...
The front cliuch is applied in 3rd & reverse.... So how is reverse?

It could be in the valve body it your lucky...
 
Reverse works as advertised. I'm heading out to the garage now so hopefully I'll have something figured out in a little bit. If it's anything more than a quick adjustment, unfortunately it'll have to wait for the weekend.
 
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Based on the steels and what you are saying I suspect the shuttle valve in the valve body.
Works like a spool valve in a hydraulic system. Travels forward and back stopping flow at some points and opening flow at others hence the shape with high and low spots.

Since it was used and not opened and cleaned internally could have debris causing it to stick.
 
Because yes that first pick is a clutch but looks like the clutch material is gone and more like a steel.
 
Broke Farmer said:
Based on the steels and what you are saying I suspect the shuttle valve in the valve body.
Works like a spool valve in a hydraulic system. Travels forward and back stopping flow at some points and opening flow at others hence the shape with high and low spots.

Since it was used and not opened and cleaned internally could have debris causing it to stick.
Click to expand...

Just went through that... Had Reverse, Neutral and Low but no upshift. Pulled the valve body, shift valve plug had some light scarring and the valve was stuck. Came out of a working transmission but it had eaten something during the rebuild.
 
I've had skid steers do the same thing. Debris get in there and gums it up and it won't slide properly on the spool and can't duplicate the problem at times. Sometimes sticks sometimes doesn't. Sometimes have to put in a new spool valve. There is usually only a couple thousandths tolerance so it can't take debris.
 
BodyBag said:
Reverse works as advertised. I'm heading out to the garage now so hopefully I'll have something figured out in a little bit. If it's anything more than a quick adjustment, unfortunately it'll have to wait for the weekend.
Click to expand...
Just take your time with the valve body. It is really important to have a very clean work bench too. Valves must move freely. Check for varnish on the valves that can cause them to stick in the bores. While it's out, get a quality shift kit installed. You'll like the better shift performance and life it can provide the trans.
 
Yup.. If reverse is fine that proves the mechanical parts are functioning... Dig into the valve body... Everything needs to be clean & everything has to move freely...
 
Update: I pulled the valve body and just as everyone guessed there was a ton of crud built up in it. Cleaned everything out and did a transgo stage 1 shift kit while I was in there. Just got it all back together and took it around the block. Reverse, neutral and 1st all work great. Unfortunately it won't shift out of first automatically or manually. I'm going to wait for it to cool down and pull the pan and valve body back off and see what I can see. Also I ordered that Tom hand torqueflite book and it'll be here Monday.

Something like this was the exact reason I was afraid to mess with the valve body when I had it apart for the clutches and I guess it became a self fulfilling prophecy. Such is life.
 
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U may need a different/used valve body. Over the years I have had about 5 or 6 valve bodies that were worn out and wouldn’t work properly. 2 even had the Trans Go TF-3 manual kit installed. Kim
 
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