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| hard jerk into reverse https://slantsix.org/forum/viewtopic.php?t=57328 |
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| Author: | kielbasa [ Fri Mar 20, 2015 10:35 am ] |
| Post subject: | hard jerk into reverse |
65 valiant 225 904 trans. When cold and choke is on, when going into reverse transmission shifts so hard it jerks the entire car and a loud thump. If I go into any forward drive gear it shifts smoothly at any idle rpm when cold. What's that mean? |
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| Author: | SlantSixDan [ Fri Mar 20, 2015 10:40 am ] |
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It's normal. Reverse is always going to be a harder engagement than Drive, 2, or 1. Check and make sure your choke and fast idle adjustments are set correctly to spec. Also, don't engage a gear until after you've kicked the gas pedal to reduce the idle speed from "fastest" to "faster". |
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| Author: | bcschief [ Fri Mar 20, 2015 4:24 pm ] |
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Check your motor mounts and transmission mount to make sure they are not broken or worn out. Brian |
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| Author: | SageRad [ Wed Mar 25, 2015 5:25 pm ] |
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Hey, i would say you should take off your transmission pan, check for debris on the magnet and in the pan, change the fluid and filter since you've got it open, and then check and adjust the low-reverse band adjust screw. That is what controls the spacing on the band that shifts the tran into reverse (as well as manual low which is engine-braking forward mode). That's my half educated guess. Anyone else think this is a good idea? I have a heavy reverse clunk right now on my old A904 tran and i'm going to adjust the rear band tomorrow as soon as the rain stops. In my pan i had a lot of very fine debris, and maybe one little splinter of steel and a few flecks of steel -- and pretty browned out but not too burnt smelling fluid. So it's been a heck of a long time since this fluid's been changed so the brown is pretty normal but time for fresh fluid, and time for the band tension check. So before you adjust it, it would be worth noting the position it was at -- in other words, to hold the square adjust bolt steady while you raise the lock nut, and then to count how many turns it takes to get it snug with a short wrench (technically 6 foot-lbs). . . . this is so you can compare to the factory spec which is to snug it to 6 foot-lbs and then back it off 4 turns. (Torqueflite A904) (A-904) (A904) Hint, not related to the reverse shifting, but another easy adjust if you have forward slippage is the throttle valve rod length adjust which is right near the shift linkage, and it's subtle so a little 1/8" change will make a difference. Take out the slack from the line and add 1/8" at a time and test, it's easy external adjustment that tells the tran where the throttle is at and therefore how much power is wanted. If it's disconnected there will be total forward slippage past 15 or 20 mph. |
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| Author: | SageRad [ Thu Mar 26, 2015 5:09 am ] |
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In terms of tools for these bands, have a magic marker for marking the adjust nut, to draw a little arrow so you can count the turns. for the low-reverse band (rear band clutch, inside the transmission): For the outside locknut, it's 9/16" crescent, and the adjust bolt is a hex head 1/4" so make sure you have 6" sturdy 1/4" wrench on hand) for the kickdown band (front band clutch, adjustable from outside the transmission near the throttle valve): For the outside lock nut i found a 3/4" to work. Deep socket and also crescent. For the adjust nut, it's a 5/16" short wrench. They say 72 in-lbs which is 6 foot-lbs, which is really if you want to get technical, "snug with a short wrench" ... that's goodenough. |
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| Author: | SageRad [ Fri Mar 27, 2015 10:41 am ] |
| Post subject: | |
Well i did the adjustment and i still have a hard jerk into reverse... |
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| Author: | SageRad [ Thu Apr 02, 2015 8:33 am ] |
| Post subject: | |
Does anyone else have ideas how to solve the hard jerk into reverse? It's making me feel like a jerk. My truck now takes its time to even shift into reverse and i have to rev the RPMs to get it to engage, and then because it's revved, it's a really hard jerk and i'm afraid it's going to destroy the band clutch or something. Any ideas? kinda desperate. It's not safe to drive when i can't guarantee that i can get into reverse when i need. |
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| Author: | SlantSixDan [ Thu Apr 02, 2015 11:54 am ] |
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Quote: My truck now takes its time to even shift into reverse and i have to rev the RPMs to get it to engage
Clogged transmission fluid filter or cooler, restricted trans fluid cooler line(s), or worn-out transmission.
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| Author: | SageRad [ Fri Apr 03, 2015 2:02 am ] |
| Post subject: | |
Thank you, Dan. I appreciate the leads. I will check this out. I just changed the fluid and the filter last week. As soon as i started driving it again, the fluid went from that nice red to a brown again. Not as bad as last time but still brown. Guess that is what happens when you don't flush. It could also be a worn-out transmission as you said, but it had reverse until yesterday morning. And it still does. It is nearly impossible to get it to engage, but once it does, it's solid. I'm going to hope that it's a clogged line. Here is some advice i found about checking the fluid flow. It is on pages 9 and 8 of this document. Quote: OIL COOLERS AND TUBES FLUSHlNG
So i disconnected the inlet to the oil cooler (on the bottom of my radiator, passenger side) the line that should be sending fluid from the transmission to the cooler. I added extra trans fluid and i idled it in neutral for 20 seconds, and got a good amount of fluid, about a quart. When a transmission or lock—up clutch failure has contaminated the fluid, the oil cooler(s) should be reverse flushed to insure that metal particles or sludged oil are not later transferred back into the reconditioned transmission. (1) Disconnect both cooler lines at radiator. (2) Dislodge any foreign material at the inlet side of the cooler with a small screwdriver. (3,) Reverse flush the cooler with a combination of mineral spirits and pulsating air under pressure (shopair). (4) Treat the cooler lines separately and insure they are clear by flowing mineral spirits or automatic transmission fluid through them. (5) Remove leftover mineral spirits from cooler and cooler lines by flowing automatic transmission fluid through them. (6) Cooler flow should now be checked by connecting the cooler tubes and placing the rear cooler tube into a 1 quart container. Overfill the transmission by 1 quart. Watching a clock, start engine (run at curb idle) and run in neutral for exactly 20 seconds. If cooler flow is less than 1 quart in 20 seconds, replace the radiator or have the radiator bottom cooler professionally reconditioned. Then i reconnected that and disconnected the line that comes out of the oil cooler (driver side) and did the same test. I got about a quart again. That tells me the oil cooler is not clogged. Then i reconnected that, and disconnected the return line at the back of the trans, and i got full flow there as well. So it's not the oil cooler or the lines. Hmm.... i really hope this trans will still work, because i'm broke. I learned how to check out this situation, though. That's a plus. Thanks, Dan. I'm gonna open up the trans and look inside again. If the band seems ok then i'll adjust it one turn to the right though i doubt that'll help. |
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| Author: | SageRad [ Fri Apr 03, 2015 6:14 am ] |
| Post subject: | |
Well i dropped the tran pan and everything looks fine in there. The fluid is fine, there's no trash of any kind in the pan, and the rear band looks and feels totally ok to me. No sign of any breakage or any heat damage. I could see the band by the servo and i could peek around the other side, too, and i squeeze the band with my hand and i see it all tighten. no sign that i can tell that it would be broke. The filter is fine and pretty clean still. So the tran was shifting into reverse a couple days ago, pretty well just a little clunk and took a little rev, and now it's totally stopped shifting into reverse, and i have no clue. I've checked the flow through the oil cooler and it's good. I'm stumped. I've been looking at all kinds of pictures from when a rear band has damage, and i can't see anything like that. Is the servo failed? Is there any seal or o-rings i could be checking? Anything else at all i can do without dropping the whole tran? Any help appreciated, because my truck is useless right now without reverse. Can't drive in a city without reverse. Should i try tighten the band a half turn or one whole turn and put it back together and see? One test i should have done is see if the engine brakes in gear 1 forward, to tell if the low-reverse band is engaging even in forward. Sage |
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| Author: | SlantSixDan [ Fri Apr 03, 2015 11:36 am ] |
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Quote: I just changed the fluid and the filter last week. As soon as i started driving it again, the fluid went from that nice red to a brown again. Not as bad as last time but still brown. Guess that is what happens when you don't flush.
That's what happens when the transmission is dead, I'm afraid. The brown is the remains of clutch, band, and seal material.Quote: It could also be a worn-out transmission as you said, but it had reverse until yesterday morning.
Well...yeah! Stuff works til it fails. :-\
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| Author: | SageRad [ Fri Apr 03, 2015 9:07 pm ] |
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Thank you Dan, for all your help. You know what? I may have lost a transmission, but i gained a lot of knowledge, and maybe even a little wisdom. That's the tuition for the school of hard knocks. My alma mater. |
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