First time rebuild problems-trouble upshifting

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TheCraigMachine

TheCraigMachine

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Just completed my very first 904 rebuild with a 998 low gear set and TF-2 kit and took it for a test drive last night. Forward and reverse engage fine, but would not upshift from first to second. This morning I backed off of the kickdown cable to the point of not having any tension on it and it would finally shift into second at about 25-30 mph with very little throttle pressure and never would shift into third. Backed off on kickdown cable even more with no change, still no 2-3 shift even up to 60 mph with motor wound up tight. Im thinking its going to be a throttle valve adjustment issue, but I followed the instructions with the kit on initial adjustment. My ATSG manual showed a spring on the back side of (from what I recall) the the TP valve, but I didnt have a spring that would physically fit in that spot. I did however end up with a couple of mystery springs that I couldnt find a home for in the VB upon reassembly. Where should I start when I drop the pan?
 
You have to have a spring between the throttle valve and the governor valve for things to work right. The TF-2 kit comes with a spring to replace the stock spring but if none in the kit fit you need to put the stock spring back in. Another issue I see that can cause very high upshift speeds is there's a sleeve on the throttle valve and you can install it backwards. It has an offset ridge to hole the throttle valve in it's proper position and if it's installed backwards it holds the valve a lot farther in.

By your description saying you had a couple mystery springs left over it sounds like the valve body needs gone through by someone that knows them to get it sorted out, or just buy a different valve body and start over. This time take pics so you get everything put back where it belongs.
 
Thanks Fishy. Thats exactly what I needed to know. Im really determined to get this thing right. All my clutches and bands are engaging correctly so Im on the home stretch as far as Im concerned. The second gear shift felt really good, Im just ready to know what third is gonna do!
 
When you get it back together, TV adjustment is full throttle/full travel. If you have a cable, make sure the pivot point distance at the transmission is the same distance as carb travel. I had to drill a hole inboard for mine, right in the middle of 'the step'.
 
Okay update. Went back through the valve body. I had the wrong springs in the shuttle valve and in the part throttle kickdown. Checked everything else, looked good and all springs have been accounted for. Even put an original throttle valve back in (the other one had been ground down as per TF2 instructions). Got it all back together, no change. I can wind it up in first and it wont shift into second unless I let off the throttle. Still no 2-3 shift, even if I push it into neutral and back into drive. As far as I can tell, the only thing left is the govenor itself. One of my manuals I have shows a spring in the govenor assembly, but mine had none when I disassembled it the first time. I was very careful to keep all of the governor componets together when I disassembled and reassembled during the rebuild. Possibly its just a piece of trash caught in one of the weights?
 
There's one other thing. The large check ball in the valve body must be 11/32" diameter. A 3/8" ball will fit in it but you won't have 3rd gear. A 3/8" ball is used on the shift detent and sometimes gets mixed up because their so similar in size you can't hardly tell any difference.

Did you install the spring in between the TV and gov valve that you said was missing and make sure the sleeve on the TV valve is on correctly so it lets the TV valve come out all the way?

With the issue your having using a ground down TV valve like the instructions say might work fine.

Just noticed the part about no spring in the governor. All governor assemblies have a spring or they won't work right. Were you able to drive this car before tearing into the trans?
 
I measured thecheck balls so I know those are in the right placces.

The TV spring is in the correct location, used the yellow one from the kit.

I realized that I didnt disassemble the governor weight itself so I didnt see the spring inside.

I measured pressures today, heres what I got.

Line pressure is 100 psi at 1500 rpm. Increases to 125 psi when TV in full forward position. Gauge exibits a bounce thats much more pronuced at idle.

Reverse servo gauge bounces wildly across entire gauge sweep, with an average 300 psi and gets higher and more eratic with TV forward.

Govenor pressures read about 5psi at standing stop. Increases with speed up to about 40 mph to a max pressure of around 20 psi. Gauge bounces rhythmically between 10 and 20 psi the entire time.

What in the hell is going on here? It acts as if though the regulator valve is not doing its job but I used the springs from the kit and adjusted it as per instructions.
 
Gonna sound funny, but is the fluid level between the marks in neutral? Might be some aeration in the fluid. Go thru all the gears slowly too, then back to neutral and check it.
 
TheCraigMachine said:
I measured thecheck balls so I know those are in the right placces.

The TV spring is in the correct location, used the yellow one from the kit.

I realized that I didnt disassemble the governor weight itself so I didnt see the spring inside.

I measured pressures today, heres what I got.

Line pressure is 100 psi at 1500 rpm. Increases to 125 psi when TV in full forward position. Gauge exibits a bounce thats much more pronuced at idle.

Reverse servo gauge bounces wildly across entire gauge sweep, with an average 300 psi and gets higher and more eratic with TV forward.

Govenor pressures read about 5psi at standing stop. Increases with speed up to about 40 mph to a max pressure of around 20 psi. Gauge bounces rhythmically between 10 and 20 psi the entire time.

What in the hell is going on here? It acts as if though the regulator valve is not doing its job but I used the springs from the kit and adjusted it as per instructions.
Click to expand...

I think your on to something. It sounds like the main pressure regulator may be sticking.

5 psi governor pressure at stand still is way too high. No wonder it's not shifting right. The pressure needs to be much lower (absolute max of 2 psi at idle, less is preferred) and it's possible the issue is with the main pressure regulator valve. That's where I'd start looking. Make sure it's adjusted correctly and not worn/scored and hanging up. My guess is you'll find it scored and hanging up necessitating replacement of the valve body. Aerated fluid as PoisonDart suggest can cause erratic readings and it's worth checking into before you tear everything apart but I have never seen aerated fluid cause overly high readings like yours are.
 
Im going to build another valve body. I have a couple of extras lying around.
Does anybody know what the shuttle valve does? The reason I ask is because one of my extra valve bodies doesnt have a spring behind (or in front of) the shuttle valve. What purpose does it serve?
 
TheCraigMachine said:
Im going to build another valve body. I have a couple of extras lying around.
Does anybody know what the shuttle valve does? The reason I ask is because one of my extra valve bodies doesnt have a spring behind (or in front of) the shuttle valve. What purpose does it serve?
Click to expand...

That sounds like a good idea. I have read everything I can find and can't seem to find a description of what the shuttle valve actually does in a torqueflite. If I'm not mistaken I've read that blocking it firms up the shifts but I have never blocked one and have had torqueflite's that shift as firm as you'd ever want one to shift. I know someone that may be able to shed more light on the shuttle valve. I'll PM him and see if can help
 
the shuttle valve controls kickdown shift feel by restricting how fast the fluid is released from the front clutchpack and the outside of the front servo.
 
william said:
the shuttle valve controls kickdown shift feel by restricting how fast the fluid is released from the front clutchpack and the outside of the front servo.
Click to expand...

So what effect would blocking it have? It sounds like it would make it drop down into kickdown a lot harder, but I also see the potential of a 3-2 flare by doing that also. If it were to relieve all pressure from the front clutch pack before the kickdown band had a chance.to apply it would flare like crazy.
 
TheCraigMachine said:
So what effect would blocking it have? It sounds like it would make it drop down into kickdown a lot harder, but I also see the potential of a 3-2 flare by doing that also. If it were to relieve all pressure from the front clutch pack before the kickdown band had a chance.to apply it would flare like crazy.
Click to expand...

.......I know it makes the 1-2 and 2-3 shifts firmer certain B+M kits and Direct Connection kits have been blocking the shuttle valves for many years..........kim...
 
oldkimmer said:
.......I know it makes the 1-2 and 2-3 shifts firmer certain B+M kits and Direct Connection kits have been blocking the shuttle valves for many years..........kim...
Click to expand...

I know they block the accumulator piston to firm up the the shifts but was unaware that they also block the shuttle valve .
 
Got it fixed. Pulled the pan again to swap valve bodies and found a piece of a sealing ring lying in the bottom of the pan, and I immediately knew where it came from...

When I intially assembled the unit, I had a lot of trouble fitting the govenor assembly into the output shaft support. I recall forcing it into place, which I now know NOT to do. Pulled the tailshaft housing (not easy to do on an early A) and govenor assembly, and sure enough, there was my broken ring. I figured that I would have destroyed the output shaft support, but luckily it survived with minimal damage. Slapped it all back together and tore off down the road, anddddd.... IT SHIFTS!!! And good too! Im ready to rebuild another one now, esp since I could just about do it in my sleep at this point. So happy!!!:cheers:
 
Great man! Always nice to hear a good engine. BTW: anytime you have trouble getting a sealing ring to slip in try using a thin feeler gauge to "walk" it in place. Also, not sure what lube you used but using ATF to lube things when assembling it is perfectly acceptable but a good trans assy lube/grease (or even Vaseline) works much better IMO
 
So after driving this thing around for awhile, Im not 100% happy with the shift quality.

At light/part throttle, the 1-2 shift is firm and deliberate, but not harsh. Exactly the way it should be. The part throttle 2-3 shift is very harsh and "snatchy". Kinda bangs into gear.

At heavy/full throttle, the 1-2 shift is kinda slow at first, like I can feel the kickdown band start to apply, and then the band fully applies somewhat suddenly and will chirp the tires. The 2-3 shift is absolutley perfect under full throttle.

If it makes any difference, I had to use a load controlled kickdown servo because my other one was missing a spring. I also did not block the accumulator.

Are there any tricks I can do to improve my full throttle 1-2 shift and the part throttle 2-3 shift?
 
My only guess is the problems are due to the load control servo. The front servo needs to apply quickly for a good WOT 1-2 shift and release quickly for a clean 2-3 shift. I rebuilt a 727 for a buddy several yrs. ago and used the load control servo and we experienced a lot of what you described. It's been so long I don't remember if it had all the issues yours has but I for sure remember the part throttle 2-3 shift was real harsh (overlapping) but fine wide open. I dropped the pan and swapped it out for an old style servo with 2 springs and it shifted great at every speed and throttle opening after that.

I can't guarantee the old style servo will fix it but that's where I'd start.

BTW: what ratio front band lever are you running?
 
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