904 rebuild problems

[Jkat]

Hi I just had my tranny rebuilt,with a few performance mods,ie. more clutches and higher line pressure, band adjustment, stage 2 shift kit . But i've noticed a few problems. If you don't gear the car manually or flat stick it in drive, it will shift from 1st straight to 3rd. Also i've noticed that when gearing down, at realtively low speeds, it makes a pretty loud 'bang'from the tranny, but it doesn't happen all the time. Apart from that it drives good under manual grearing.

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[ChristianCuda]

It sounds like your kickdown linkage or kickdown band is out of adjustment. If there is not enough pressure on the kickdown band it will shift right from first into third.

Christian

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Http://ThunderRacing.Knudstrup.net/

68 'Cuda 383 Best of 13.249@103 with a 1.916 60ft (now 13.20@105 but 2.03 60ft with 3.91 gears and tire slip)
(Formula S recreation not original but making like they should have at the factory) Working on adding EFI
69 'Cuda Race Parts Car
76 Duster 273 recent transplant
95 Neon 2.0 SOHC best of 16.96
84 Dodge Ram D50 transplanting 360

[rather]

I will side with cuda on this one. When my backlash removing spring on my kickdown linkage broke the second gear started slipping and within 10 minutes the second gear failed completely and is still gone after replaceing the spring and readjustin gthe linkage. Don't take chances with it.

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1987 Dodge D100, 2wd, 3.7 Slant Six, California Certified, Automatic A904, 2.9something rear gear, K&N Filter Charger, Jacobs Electronics Pro-Street Ultra Team Ignition sytem, Autolite Plugs #25, Basic Timing Set To 14 degrees. Chevron supreme Gasoline, Castro Synthetic 10w-30 Motor Oil, Valvoline Synthetic Rear End Oil,
American Racing Wheels AR-767 15x7, Fully Loaded Clifford Alarm System, and now at 121,250 miles

[Jkat]

The car drives and shifts fine on WOT and on manual gearing, and yes on wot the kick down linkage is fully enganged. But in drive with little throttle is where the problems are.The oil level is slightly above the idle hot HI line. I also noticed some other weird behaviour from the tranny yesterday morning when it was cold,it held first a little to long in drive then 'popped' 'banged'loudly once and then went straight to 3rd, and latter that day again cold, while driving of from standstill it seemed to go in neutral for a split second then jolted back into gear again? Apart from that it drives shifts fine.
Thanks for your help guys, down here in Aus there isn't much expertiece with the 904 TF

[Jkat]

I have also noted since driving it again today that I have no partial throttle kickdown. I did some research, and looked at some valve body diagrams, and most things that I read point to the 2-3 shift valve ,mainly the spring or the throttle pressure plug at the end of that valve. I'm thinking that if the spring is missing or broken, the valve will slam from one side to other when you upshift or downshift abruptly, which is what I have heard as a pop bang.I think the governer works ok because on wot in drive it changes 1-2-3 at 5500, perfect.
What do people think, is this legitimate, so I can start unbolting the pan and valve body?

[ChristianCuda]

I still say to adjust the kickdown linkage more because I of the fact that at WOT it shifts normal and no kickdown means that the lever is not being pushed back far enough to activate it. At Idle the lever should be pushed back about 1/2 inch. At half throttle it should be pushed back a little over halfway and full throttle all the way back. What is happeneng to you is that the kickdown is not being pushed back to over the halfway point at half throttle most likely it is really only 1/2 inch back at that point. Adjust it properly and I bet everything will feel better. Now you may have already messed up some items by driving it this way.

Christian

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Http://ThunderRacing.Knudstrup.net/

68 'Cuda 383 Best of 13.249@103 with a 1.916 60ft (now 13.20@105 but 2.03 60ft with 3.91 gears and tire slip)
(Formula S recreation not original but making like they should have at the factory) Working on adding EFI
69 'Cuda Race Parts Car
76 Duster 273 recent transplant
95 Neon 2.0 SOHC best of 16.96
84 Dodge Ram D50 transplanting 360

[Jkat]

Sorry I forgot to mention it kicks down by pedal normally, and holds the gears until 5500rpm, but the way I have kickdown is @ idle throttle lever full forward, @1/2throttle lever 1/2 back, and @ wot lever full back.

[Tim_K]

I'll mention a few problems I've had with my new 904 I rebuilt, see if any of this applies to you.
As part of the shift kit installation, one of the modifications was to put in a heavier spring on the torque converter control valve. The kit says the stock spring can let the converter aerate under some driving conditions because it loses its pressure charge. This equals an inefficient converter while it happens. Well, it sounded good enough, but the only problem now is that with the converter getting more high pressure oil, stall speed has fallen from 1850 to 1700 in my /6 '71 Valiant. Even with the wide ratio low gear, off the line acceleration is down. It needs a high stall converter now more than ever.
Second problem. The kickdown performance has changed. When I put the 904 back in, I used the original kickdown lever down at the trans., and it just wasn't enough. I had to adjust the kickdown so it would be all the way back when there was a 1/2" more throttle travel left. I changed to a kickdown lever off a 727 (360-2 truck trans.), and that helped some with the 3/8" longer center to center measurement between the pivot and lever holes in the arm, but it needs even more to be right. I'll have to cut and weld together 2 kickdown arms to get it long enough. The K.D. will need to be about halfway back at idle, then all the way back at full throttle. As it is now, to get it to kickdown in traffic sometimes it needs to have the throttle pressed down most of the way, then of course it kicks down hard, the engine screams, then you let off and it shifts back up before you want it to. Although I did a good thing with putting in 4 disc clutches and the rebuild in general, I'm starting to think the shift kit was a bad idea, unless a high stall converter is added at the same time.

[Jkat]

Yes ,the kickdown needs more travel than before, it only kick down at wot. I think the partial throttle kickdown wich is factory doesn't work any more. The stall converter pressure sounds interesting, I wonder if you could manualy control this valve and reduce the oil pressure on take off and then increase it again, ie. a cheap high stall and effeciency at wot as well.

[Dennis Jokela]

I WOULD SUGGEST THAT YOU REMOVE THE VALVEBODY, AND REPLACE IT WITH A STOCK ON. ADJUST THE BANDS SO THEY HAVE ABOUT I/4 IN. OF SIDEWAS MOVEMENT. IF YOU NEED A {SHIFT KIT} I WOULD RECOMMEND THAT YOU BUY A CHEETAH MANUAL OR PERFORMANCE VALVE BODY. I HAV RUN A MANUAL VALVE BODY ON THE STREET FOR YEARS, AND HAVE HAD NO PROBLEMS AT ALL. IT IS ALSO FUN TO DRIVE, AND THE SHIFT QUALITY IS UNREAL.

GOOD LUCK:

[Morris Brown]

On these transmissions I have had problems with these before. The most common problem was grit in the governor causing it to stick. This will give it some weird behavior. Want to know something scary? Many moon ago pontiac had a transmission called the slim jim. It had no torque converter. When the governor stuck on it, it would not down shift into low when you pull up to a red light. Like forgeting to push the clutch down on a straight shift. But try cleaning out the governor and check it for freeability. This is usually the fix. If not you have spring trouble in your one to two shift valve.

[Jkat]

Thanks for the replys guys, iv'e taken the valve body off and found no obvious faults, springs ok, shift valves move ok. I haven't cleaned the governer yet, but what makes me think it's not that, is when at wot the tranny shifts gears at 5500 rpm consistently in 1 and 2, so it seems to work fine. What I have to find is the cause of that popping sound.