Rebuilt A-904 Sluggish Response

Moparmann · May 11, 2021

The 904 in my 70 Charger 500 was rebuilt during previous ownership. The problem is, once the car has been sitting a while, the transmission has to "pump up" before the car will move. I've also experienced this w/ other rebuilt Torqueflites as well. This is annoying and dangerous especially when entering traffic from a driveway. The transmission in my other Mopar is original and no matter how long it has been parked, it IMMEDIATELY responds to the accelerator. Is there an easy resolution to this problem?? I had (but misplaced) a magazine article about this problem. Any help/advice would be appreciated!!

493 Mike · May 11, 2021

Certainly not normal.
Mike

74gtx · May 11, 2021

It sounds like the converter is draining back into the transmission. I usually put my car in neutral for five or ten seconds after I start it on it drops into gear solid.
Good luck! Mike.

bandit67 · May 11, 2021

Torque converter leak down is what it sounds to me also...why, but I don't know how tqs are made in that some do , and some don t. Maybe some tranny rebuilders can tell us, is it the way the tq is made or is it the tranny itself that lets the fluid flow back.

Moparmann · May 11, 2021

@ Mike: It goes into gear solid, but stepping on the accelerator produces high rpm for a few seconds before there is movement.

Moparmann · May 11, 2021

@ Bandit: According to the lost article that I had, when rebuilding, there is something that can be done to prevent this happening, but most rebuilders don't know how, or just don't do it IIRC. *SIGH*

Purepony · May 11, 2021

Yeah that doesn’t sound like something any trans should do.
All my old school trans have always moved when o press the accelerator even if there’s a slight second delay but probably no more than that

OKDart · May 11, 2021

The shop that rebuilt a 727 for me long ago showed me a print out of a TSB with a corrective action for torque converter drain back. They said they accomplished the TSB. It still had the drain back issue.

Just put it in neutral for a few seconds before going into drive for the first start of the day.

Curiousyellow71 · May 11, 2021

Possiblity some rings broke w the installed the pump into the front drum. It's the first place I would look. Usually causes it to leak internally and struggles to build pressure till you rev it up. If its worse cold that would also be a sign.

Dave6T4 · May 11, 2021

Nowadays, we drive our old 727-equipped cars infrequently, allowing the torque converter to drain back between uses. When the cars were new and being used daily, the converter did not have a chance to do this. As others have stated, the trick is to start the car in neutral and let it idle for a few seconds before pulling into gear. The converter will not refill while in park. Years ago, I bought a kit that contained an " upgraded" manual valve that was supposed to cure this drain back condition. After I installed it, I saw no improvement.

493 Mike · May 12, 2021

Transgo makes a kit called the "Noyoyo" solution that does allow the converter to fill in Park. I have installed many of them with good results. A lot of converter drain back is caused by a loose hub to pump bushing fit. Transgo has a fix involving the use of a different pump bushing. I have found in, especially 904s, the rear clutch does not engage due to leakage in it's hydraulic circuit. Could be seal rings, piston seals, VB issues, or case porosity of some sort.
Mike

Moparmann · May 12, 2021

Thanks for all the replies! I will give the idle in neutral a try! :thankyou:

74gtx · May 13, 2021

Good luck. Let us know if it works.

Rebuilt A-904 Sluggish Response

Moparmann

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493 Mike

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74gtx

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bandit67

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Moparmann

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Moparmann

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Purepony

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OKDart

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Curiousyellow71

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Dave6T4

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493 Mike

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Moparmann

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74gtx

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