No 3rd shift in 904 after rebuild..

[TrashedCharger]

This is a '72 and up unit A-904. I just finished cleaning and rebuilding everything, but I'm not getting third gear. 1-2 shifts fine, but I do have reverse.

The band and clutch apply chart show that the front clutch pack is only engaged in 3rd and reverse. I thought this may be the issue, but it's getting reverse just fine.

I drained the fluid and pulled the valve body. I double checked everything in the vlave body. Everything seems to look good to me in accordance to the factory manual I have.

I did an air pressure check. Front kickdown band, rear low/reverse band, and rear clutch seem to be operating good. the front clutch (2-3shift) seems like it resists the air pressure a bit more when I apply it, but I'm not sure if that's normal. I didn't fight anything putting the clutch rings and steels into the retainers. I did it all by hand and was able to index them all by hand with no resistance in turning them.

I used the thicker clutch rings in the front clutch assembly and the thinner ones in the rear. Is this correct?

I'm starting to think that I'm getting too much kickdown. The kickdown is only applied in 2nd gear and I didn't run it fast/ hard enough to see if it would go into third at a higher speed in fear of hurting something, but I am not getting kickdown shift when I hit WOT right after it goes into 2nd at low speed. This also makes me want to believe that I'm getting too much kickdown.

I'm going to double check my band and linkage adjustments tomorrow when I have daylight to work under, but does anyone have any experience with this problem?

I know it's not any hard parts. I soaked the clutches for at least an hour before assembling it, shifted it through all of the gears, checked and topped the fluid off in neutral. I've never quite run into this particular problem on other trans rebuilds I've done before.

Any pointers would be great. I haven't deducted that it could be something in the valve body. I didn't touch the pressure adjustment screw. Just disassembled everything and put it back how it was. All of the bearings are in order, etc.

Thanks in advance.

Dave

[peg leg]

Have you driven enough to ascertain where it shifts to second? It should shift at around 15 MPH with light throttle pressure. Sounds like the kickdown to me, too.

[70AARCuda]

what about the throttle pressure linkage...if it is misadjusted it will not allow trans to shift into 3rd gear..

disconnect and drive around block..see if trans shifts into high gear....the shifts will have fast ....

[TrashedCharger]

I haven't conducted much of a test. Come to think of it. I know I'm not getting kickdown at WOT. My speedometer reads 5mph high at all speeds. I restored my dash and haven't corrected the clock position of the needle, so it was reading 20mph when it shifted into 2nd. What you said just reminded me that the speedo is off.

I know how the kickdown is supposed to be adjusted, but I think I'm going to blueprint it from scratch and just make sure it's perfect. On this model, you use a 1/8" dowel to lock the upper pivot joint in place and make sure the lever on the trans is wired or held forward, with the carb off of fast idle to set it at zero.

I'll conduct the kickdown test after I get everything adjusted and make sure it's wired forward when testing it at low speed. I know that it should hit 3rd at low throttle/ idle at about 17-20mph.

I'll see what happens. I just hope it's nothing foul in the driveline. I'd hate to have to take this thing out to get to something, but I will if need be.

[TrashedCharger]

So, after tripple checking my kickdown band adjustments and resetting it to two turns from 72 inch pounds tight (6ftlbs) wiring the kickdown lever forward and just cruising off of idle, I have determined that it is not the kickdown causing the mis-shift.

I am getting absolutely no unneded kickdown, what so ever. I know this for a fact, now.

So that means that the problem is either something wrong with the valve body, the passage that goes to the front clutch or the front clutch itself.

And I'm starting to think that maybe there might be some gunk or some debris in either the valve body or the passage, something isn't installed correctly in the front clutch assembly, the line pressure is too low or something isn't doing what it should be doing in the valve body.

I am still getting reverse perfectly, which leads me to believe that the front clutch is working properly. It has to be engaged for reverse, but is it possible to have reverse if it isn't engaged? I don't think it is, because usually when the front clutch pack wears out in these, you lose third and reverse, but you lose third before reverse.

I remember hearing somewhere that the reverse circuit has a higher operating pressure, which is why I was thinking it might be low pressure.

I really don't think that the clutch is improperly assembled. This seems like some issue with the line pressure to the front clutch operating piston not being up to what it should, for whatever reason.

It shifts from 1-2 fine at idle/low throttle at about 15mph. It tries to go into third gear, but it just hits like a false neutral or first. So I think the governor is doing what it should and it seems to me like the valve body is doing what it should, but something is just not engaging those clutches enough in 3rd circuit.

Has anyone had this problem before?

[John Kunkel]

First thing to do is pull the VB and air check the front clutch. If there is no/minimal leakage in the clutch circuit it could be the VB.

No 3rd gear right after a rebuild can be caused by the absence of a check ball in the VB; in the main casting there are steel balls sitting in "canoes", all of the canoes take a 1/4" ball excerpt for one that takes a larger 11/32" ball. If the large ball is left out there will be Reverse but no 3rd.

While the VB is apart check the 2-3 shift valve components for freedom of movement in their bores.

[TrashedCharger]

I'll do that John. Thank you so much for the info on the front clutch.

I did an air pressure check when I had the VB out a day ago after the initial test drive. The front clutch resisted air pressure more than the other orifices that lead to the bands and the rear clutch. It had no air leakage.

Will reverse work without the front clutch engaged? I don't think it will, and I have reverse, so I think the clutches are fine. I put the thicker clutches up front and had absolutely no problems putting them together by hand. The gap checked out fine and I was able to index the clutch rings by hand with a screwdriver to get them assembled in sync with the drive shell and pump, etc.

It went together without any trouble.

Do you know if there are different fluid pressures in that front clutch circuit from the VB in reverse and third?

My friend said that he had a 904 done and it wouldn't go into third, took it back to the shop and they found some piece of gunk in it.

I'm starting to think that this is a VB problem, because reverse is perfect. I really hope it is, because I don't want to drop the exhaust and everything else again to drop this thing and have to buy another pump housing seal, etc.

I'll double check the VB and bearings in the valleys. I pulled the 1-2 and 2-3 piston spring stop plate from the VB to inspect the piston and blockers to inspect them. Is the schuttle valve symetrical? I guess I'll have to look.

The Service manual I have is for my '68 Dodge Charger and the VB looks almost the same with the exception of one part that attaches in place of the plate where those blockers on the 1-2 and 2-3 valves go. I'm not quite sure what that does, but I would imagine it has some sort of control over the schuttle valve? not sure.

anyway, I have another VB in another 904 that hasn't been apart that came out of a numbers matching '73 Charger. The 904 that I'm working on is in a '73 Scamp. It's probably identical. It has the 4 gear planetaries. Maybe I'll take that one out of that trans and blueprint this one to it. Maybe something hidden got lodged in the VB. I didn't take it apart last time, with the exception of the shift valves to inspect them with the same thought you had.

I'll check it again with a fine toothed comb this time, because I have reverse and those clutches are brand new.

[pcrmike]

The governer on the output shaft is what controls the 2-3 shift, and a grain of metal or dirt in it will cause it to either not shift there at all or go all the way to redline to get it to shift. My moolah is on the governor. :-) PCRmike

[TrashedCharger]

Doesn't it control the 1-2 shift as well? That isn't too difficult to get to either, I suppose.

I can check it's alignment, etc as well. Maybe I'll do that before pulling the valve body again. Get a jack and a board under it, drop that driveshaft and take a peek at it.

[pcrmike]

John Kunkel likely knows the answer to this one with his eyes shut, but seems I recall the governor being used on the 2-3 only. I have a Caravan that uses it on both upshifts, but outside of the valve body, that was the first thing that popped to mind. :-) PCRMike

[John Kunkel]

Originally Posted by pcrmike

The governer on the output shaft is what controls the 2-3 shift, and a grain of metal or dirt in it will cause it to either not shift there at all or go all the way to redline to get it to shift. My moolah is on the governor. :-) PCRmike

It appears that the governor is working correctly sinced Trashed stated "It tries to go into third gear, but it just hits like a false neutral or first."

This tells me the 2-3 shift valve has opened and the the kickdown band has released but the front clutch isn't engaging; if the KD band releases and the clutch doesn't engage the trans is basically back in first gear.

The line pressure in Reverse increases by a factor of about three so a weak clutch can work OK in Reverse but not in 3rd; if major leakage was the problem it would show up on an air test.

It's looking more like a VB problem.

BTW, the casting that takes place of one of the steel cover plates on the VB is the Part Throttle Kickdown (PTK) module. It is used on /6 904's and pretty near everything from '71-on.

[pcrmike]

I had missed that part, John. Also, could a notch or nick in the seal that leaks allow it too, if it ups the pressure in reverse? Enough to hold it, but at the reduced pressure, leaks off too fast? :-) PCRMike

[TrashedCharger]

I didn't notice any leakdown in the front clutch when I did an air pressure test. In fact, it felt like it resisted the air pressure more than any of the other orifices that went to the bands and the rear clutch pack.

The clutches and steels are raybestos parts. they were soaked for an hour before installed and don't have any more than three miles on them, with, appearantly, no use, other than going into reverse.

That is exactly what it does, though. It shifts into 2nd at 15mph with zero throttle kickdown and when it reaches shift point to go into third, it goes into first.

I'll drop the oil tomorrow and pull the valve body to see if I misplaced a bearing or if it's got anything in it that shouldn't be. I may just take it to a friends shop and have it put in a parts washer before reassembly. I cleaned it out really well in a can of laquer thinner, but maybe I'll go over it again with my air compressor and blueprint it to the other valve body that I have that I know is right.

I mean, this trans slipped before, but it had third and reverse with the clutch steels that were worn down to the steel when I pulled them. I changed the trans fluid religiously because of the problem and put a magnet in the corner of the pan, so by the time I dropped the fluid to rebuild it, the fluid that came out wasn't gross. I still cleaned quite a bit of aluminum sludge from the valve body and in the servos, though.

I wonder how many times I can take a cork gasket off and reuse it? hahaha...

I have two other gaskets that I can use from the other rebuilds that I used the 727 pan gaskets for. Man... I hate transmission fluid... I don't wanna... hahaha...

[MOPEkid]

Hey, BTW, where can you find good gaskets (cork or otherwise)? I just put in a new rubber gasket on my 904 and it still leaks like heck (especially when it's been sitting for more than 12 hours or so).

[pcrmike]

TC, it resisted air, but did it engage? Did youhear the "thunk, whoosh, thunk whoosh" of air engaging, and let off of it as it worked, or was it quiet? :-) PCRMike

[John Kunkel]

Originally Posted by MOPEkid

Hey, BTW, where can you find good gaskets (cork or otherwise)? I just put in a new rubber gasket on my 904 and it still leaks like heck (especially when it's been sitting for more than 12 hours or so).

If it leaks more aggressively after sitting it's probably not the pan gasket, converter drainback causes the fluid level to rise when sitting.

Leaks that originate above the pan will often run down to the protruding pan gasket before dripping off. Get some spray brake clean and thoroughly clean the case, then look for fresh fluid.

Common leak points above the pan are the dipstick tube, shift shaft seal, NSS, speedo cable, cooler line/fittings, rear band anchor pin. The last part is hard to see and will often simulate a pan gasket leak; the end of the shaft is at the rear of the case just above the pan rail.

A mirror and strong light are needed to find most leaks.

[pishta]

Originally Posted by John Kunkel

.....
Leaks that originate above the pan will often run down to the protruding pan gasket before dripping off. Get some spray brake clean and thoroughly clean the case, then look for fresh fluid.

Common leak points above the pan are the dipstick tube, shift shaft seal, NSS, speedo cable, cooler line/fittings, rear band anchor pin. The last part is hard to see and will often simulate a pan gasket leak; the end of the shaft is at the rear of the case just above the pan rail.

...

Ooh, that was where mine was leaking, the rear band anchor pin. I thought it was a fluke, but apperently not! Slap some MIGHTY PUTTY on it, good to go!

[TrashedCharger]

It was a bit quieter than the other clutch pack, but I could see and hear it engage. I put air pressure on it and when it was under pressure, it would resist moving more than when it had no air pressure.

I thought maybe something was jamming in the piston too, but if that were the case, I don't think I would have reverse.

I'm going to drain the fluid here in a little bit once it cools down outside and see what I can see in the valve body. If that doesn't prove anything, the only other thing that I could possibly think of would be that without knowing it, I'd have put the thicker clutch steels in the wrong pack.

And the only reason I don't think that is the case, is because the steels themselves are the same thickness, front and rear, it's just that one set has more material on them than the other. And when I pulled the old clutch packs apart, the front one was down to the steel on one ring and they were all very thin and I still had third, albeit did slip and would slip into reverse as well when cold before I went through this thing.

Start with the easiest and go to the most difficult thing to do (pull the trans and pull the clutch packs)... hahaha... oh well... we'll see what comes of it!

Thanks again for the input, Mike.

As far as the pan gasket goes, from my experience with this transmission and others, what I noticed, is after the converter drain back, it would actually leak from the dipstick tube.

Whatever you do, don't overtighten that pan gasket. What I usually do is refill the trans when the car is still up, hold the rear brake, shift it through all of the gears, then set the E-brake and top it off while running in neutral, then shut it off.

Then I crawl under it and look to see if there is any weeping around the bolts and tighten the ones I notice weeping if any, go around the entire gasket and check them all again. You should only need about as much torque as it takes to tighten a valve cover. like 15 ft lbs. a standard 3/8 drive ratchet with an extension and socket with one hand should suffice.

I'd put money on your dipstick tube O ring being the leak culprite. You'll lose about one and a half to two quarts of oil and it will stop leaking any more than that if that's the cause.

That O ring in the base of the dipstick tube that pushes down into the trans case is probably shot. You have to take out the bolt that holds the bellhousing to the block, that sandwitches the dipstick tube brace. Then just wiggle it and pull it out.

If you do this, be sure to put a catch pan under the tube openning to catch the oil, because the oil level is above that junction. You won't have to pull the pan to drain it again and ruin your gasket, just be sure you have the car a bit nose down so when the oil level above that tube drains out, it doesnt want to run back across all over the transmission case and make a mess. You want it to drain forward and if anything, a bit off to the passengers side.

Before you pull the dipstick tube, blast it with degreaser like John said, so no rocks or grease get down into the tube openning and into your pan. It may also pay to stuff a clean paper towel or rag in the hole while it's out. When the tube goes back in with the new o-ring, dip it in some trans fluid first so it goes in without fighting it.

Just go to Napa or Car Quest and get the O ring you need, or spend about $7 and get the pack of multiple size O rings that Checker or AutoZone has. They are handy to have around and the right size should be in there. There are two alike in that kit, it's the slightly smaller of the two if you go that route. Just be precise with the thickness and diameter when you select the O ring and you should be fine.

[MOPEkid]

Ah, thanks, I'll check the o-ring and the other things John Kunkel mentioned when I go to get my alignment done. Sorry to interrupt!

edit: I went out and looked at the transmission just now and there seems to be a decent amount of fluid leaking from the front of the transmission, possibly from the part where the engine connects to the bellhousing. It may also have leakage in other places, as the transmission is "damp" (the layer of grime looks wet) above the pan.

[TrashedCharger]

You probably have a combination of a rear main seal leaking, along with that o-ring. It could also be a front seal on the trans. Best to start with the easiest and cheapest thing first.

As far as this 904 goes...

I pulled the valve body just a few hours ago.

I also pulled the valve body from the other '73 904 from the garage and used it as a map to disassemble and reassemble mine.

I blew the small passages out with my air compressor. I didn't notice anything in them and all of the valves moved freely as I reassembled it to match the other valve body.

I had/ have all of the valve bodies bearings in place where they should be and all of the springs are exactly where they should go.

The one difference that I noticed between the two valve bodies is that the one that came out of the Charger that was in my garage, seemed to have a tighter throttle pressure screw adjustment. along with a tighter stop screw adjustment. The valves are identical from one to the other, I would only assume that maybe this is because it came out of a heavier car and possibly calls for a higher throttle pressure?

I left the one for the 904 that is in the Scamp where it was at.

Also, I wouldn't think that throttle pressure would have anything to do with this issue, seeing as how I had the kickdown wired completely off.

I did a test drive around the block under low throttle or idle and I'm still getting the exact same problem.

It's shifting from 1st into 2nd at around 12mph and from 2nd into false 1st/should be 3rd at about 18mph.

If this were an issue with the governor, wouldn't it simply hold it in 2nd, or would it keep the pressure down too low to engage the 3rd/reverse clutch pack?

I'm still getting reverse without any hesitation off of idle at about 550-600rpm. I know this clutch pack is engaging fully in reverse, but there is definitely some kind of low pressure issue in the 3rd engage circuit.

The only other thing I could think of would be to do go to the hardware store and cook up some stuff to do a hydraulic pressure test or see if I can't rent or buy a gauge and the fittings to do it myself. It doesn't seem too difficult of a proceedure.

I'm starting to wonder if this front clutch pack is just not sealing or has a weak piston, for some reason?

Is there any way to adjust line pressure? I know you can adjust the throttle pressure, but would that have any effect under zero kickdown?

I'm really leaning towards pulling the transmission out at this point.

[TrashedCharger]

So... I'm digging this thread up just to post my findings.

I went through the governor valve and discovered a slight burr in the 2-3 shift valve bore that I corrected, but that didn't help much, although it needed corrected. I think it may have happened when I was trying to install the e clip on the retainer rod that goes through the entire assembly, but it does it's job now.

I ended up pulling the transmission apart and replaced the front clutch piston seals that didn't come with the kit (and was supposed to)...

When I pulled the spring out and then the piston, the seal came out in about five pieces. The inside of the seal was completely separated from the outside and I'm sure that was the problem. The inner piston seal looked good, but I replaced it with a new one anyway.

I got the transmission back in and everything works perfectly now.

So, in conclusion, after dropping the fluid five times and test driving it at least that many times after refilling it when you buy a rebuild kit, make sure that even if you have no leftover parts, that you go through the checklist first. It may save you an extra trip or five under the car... ugh...

[pcrmike]

So it WAS teh piston seal. Give me a little gold star. No,really, I am just glad it is working again for ya. Congrats. :-) PCRmike

[John Kunkel]

I'm surprised that a torn seal didn't show up as a blowing leak on the air test.

[TrashedCharger]

I think I figured out why it didn't show on the air test, John. What Mike said about the engagement got me thinking...


I may have had the pressure of the air up higher than 3rd gear engages in. Although air pressure and fluid pressure are very different, for whatever reason it was above the required pressure for 3rd. Now I know what a blown seal feels and sounds like. I think if I had the pressure lower, it may have bled off. I thought it would bleed off more with higher pressure, but who knows what the hell that mutilated seal was doing under different pressures.

See, I was reluctant to replace that seal, because it was getting reverse just fine, but I looked into the pressure charts and it looks like reverse gets almost twice the fluid psi that 3rd gets in that clutch pack.

So, for instance, say that piston got 40psi applied in 3rd and 80psi in reverse. That means the piston requires at least 40psi to engage the clutches. Even though it should have more pressure for higher torque in reverse, I was getting something.

So, say if that piston seal were leaking 20psi. That would drop the 3rd gear circuit down to 20psi and the reverse circuit down from 80psi to 60psi. So now reverse is still getting the minimum required pressure to engage the clutches at all, but 3rd gear is not.

I'm sure it's not an exact science, because like I said, who knows what that rotten seal was doing under different pressures, but I'm pretty sure that this was what was happening, more or less.

Oh well. I know the thing inside and out now and have the bolt hex sizes memorized for everything. I also know that any pan gasket, rubber, cork or paper will re-seal four times under low use. hahaha...

I think I can get a transmission pulled and installed inside of six hours in an A body with hand tools, laying on the ground, now. hahaha.

[TrashedCharger]

The best part was after I finished the transmission and gave the car back over to Lauren to get her to school, I forgot to reconnect the fuse for the stereo deck and when she got it home, the ignition coil went out. ahhahaa..

Easy fix, but it's just murphy's law. hahaha...

[John Kunkel]

Originally Posted by TrashedCharger

So, say if that piston seal were leaking 20psi. That would drop the 3rd gear circuit down to 20psi and the reverse circuit down from 80psi to 60psi. So now reverse is still getting the minimum required pressure to engage the clutches at all, but 3rd gear is not.

The Reverse boost raises the line pressure by a factor of at least three, on the later models the boost is set at 260 psi; that's why good Reverse operation isn't always a sign of a good front clutch. The air test usually sorts it out.

Add to that the fact that cars aren't usually throttled high in Reverse (except in the movies).