904 2-3 shift flare

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Wheel Chock

Wheel Chock

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I'm about to start on the rehab of my Duster and 1 of the many things that I have to deal with is rebuilding the wide ratio 904. This trans was built about 12 years ago by a friend/tech at a local Dodge dealership. After installation it had several problems that I can't recall any more, that led to me removing it and disassembling it a few times. Eventually all of the issues were fixed, except 1, RPM flares during the 2-3 shift, when the shift is made with the lever in D. This only occurs at full throttle. In normal driving or when shifted manually, it shifts okay.
My question is, when I tear into it, what should I be looking for, specifically?
I'm probably going to switch to a manual valve body, but I want to make sure that the problem is fixed, not just band-aided.
I will be doing the work on the trans myself.
 
No the KD isn't the issue, the adjustment has been verified several times and the kick-down functions normally.
I've been driving this thing off and on for over 10 years. It was my daily driver until the mighty 318 finally wore out.
 
I believe that I have eliminated any possible external causes and the trans needs to be torn down regardless, I'm just wondering if anyone has any insight into specific areas that I should look for during the inspection.
 
The timing of the front band and the actuation of the front clutch are the main areas of concern. What's happening is that your front band is releasing before the clutch is applying. Maybe the band is worn out out of adjustment. This is a freebie to try and tighten it, so if it doesn't fix it, there's no harm done. Usually there isn't much that stops or slows down the actuation of the front clutch except for throttle pressure. Possibly but doubtful a sticking valve. In that case I'd go with Trans-X
This adjustment right here.
LinePressureAdj.jpg


Or, it may simply be a dirty filter.
My personal advise is that if you don't intend to do a full rebuild, you should reuse the old fluid as opposed to using new fluid. That statement should bring the boys out of the woodwork, but I'll defend it to the bitter end.
 
Leadfoot said:
The timing of the front band and the actuation of the front clutch are the main areas of concern. What's happening is that your front band is releasing before the clutch is applying. Maybe the band is worn out out of adjustment. This is a freebie to try and tighten it, so if it doesn't fix it, there's no harm done. Usually there isn't much that stops or slows down the actuation of the front clutch except for throttle pressure. Possibly but doubtful a sticking valve. In that case I'd go with Trans-X
This adjustment right here.
LinePressureAdj.jpg


Or, it may simply be a dirty filter.
My personal advise is that if you don't intend to do a full rebuild, you should reuse the old fluid as opposed to using new fluid. That statement should bring the boys out of the woodwork, but I'll defend it to the bitter end.
Click to expand...
 
Thanks Leadfoot, I will look closely at the valve body when I remove it. I don't think the filter could be the problem because, even after 10+ years of use, there aren't a ton of miles on it and problem has been there from the beginning.
I will do a full overhaul any way, because the old 318 is getting replaced by a 408.
 
I had the same timing problem in my 904 for 3 years and it was fixed by removing the inner spring on the front servo.
 
It's been so long since I had this trans apart that I can't remember if that's has been done or not, I'll have to check it.
 
I reuse fluids. Got containers marked in quarts just for that. Dont allow the bottom of the pan to drain however. Thats got the muck.
 
If the tranny is installed, I highly recommend a full pressure test.
The same oil circuit that engages 3rd, also disengages 2nd.So either the Hi-drum is slow to engage, or the 2nd is releasing too early. Or friction surfaces are slipping.Possibly due to a lack of oil pressure, or mechanical issues.So if the tranny is out, I personally would tear into it and figure it out.
 
I agree with A/J. If it's still in the car pressure test it first. That way you'll know more when and if you do tear into it. One thing I'll tell you that I've ran into on some 904's that cause shift flare up (can cause 1-2 or 2-3) is a warped front pump. I've had 2 that were warped and not producing the pressure needed. A pressure test will give you an idea if that's a possibility, although it's not the only part that can cause low pressure. The main pressure relief valve in the valve body also can cause low pressure. Do you know if a shift improver kit was installed?

BTW: if your rebuilding it to handle a 408 want yrs of trouble free service I'd recommend that you make sure it has steel planetaries. I've seen aluminum planets give out from all the torque a stroker produces. When I built my 904 to stand up to my 408 I got all the needed goodies from www.wittrans.com at great prices.
 
Also, be advised that the wide-ratio planetaries must be matched to an output shaft designed to receive them. What I mean is that the wide-ratio stuff is different from the regular stuff. The spline counts are the same, but the shape of them is different. I found this out the hard way;Ziiiing!
Oh yeah I eyeballed those wide ratio parts for a very long time and could not see any difference, to the regular stuff. So I went and got me another core, and still could not see a difference.So I pulled a regular 904 apart, and could not see the difference. So I researched it, and discovered the shape difference, and I could not see it. So I got out my magnifier, and could not see a difference. So I stripped out a slanty lockup tranny with the wide ratio stuff, and put the matched shaft and planetaries, into my teener case and problem was solved. Then I put the teener wide ratio shaft back into the wide-ratio slanty case , buttoned it up and threw it back into the shed. The stripped out rear aluminum planetary of course was junk.Then I reassembled each of those other cases, each with it's own matched sets. What a pile of work, phew!
 
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Leadfoot said:
I get beat up a lot for telling people that I do that. I only do it with transmission fluid. Sometimes antifreeze if it's new.
Click to expand...
I'll do that with the oil out of my blown 470" hemi. on alcohol. See,if for some reason I cant let it warm up completely,the oil gets polluted with alky. Put the oil in a big pot and over a outdoor fire pit. Monitor the temp and boil the alky out. At14 quarts an oil change it can get costly.
 
Leadfoot said:
Careful! The Revenooer Man might confiscate your still.
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Thats good! I've actually thought about doing that as I have about 30 gallons thats milky with water. Sat to long. Distill the alky out of the water. You know that stuff isnt disposed of easily. Been told to burn it. That would take a while.
 
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