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| Continued from Social page: Sluggish Gear Engagement https://slantsix.org/forum/viewtopic.php?t=38568 |
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| Author: | wjajr [ Sat Jan 09, 2010 11:48 am ] |
| Post subject: | Continued from Social page: Sluggish Gear Engagement |
It has been well over four weeks, perhaps six, since the last time I started this car. Today I performed a preliminary start-up in preparation for a trip tomorow of 90 miles to new heated storage. I have never started her in cold weather (20*) before, and she did not disappoint. Equipped as follows: 1977 A 904, new automatic/manual valve body, new 2600 stall torque converter, new filter, fluid, seals, and band adjustment. When car is used several days a week there is no noticeable engagement problem, and never any slipping in any gear. Me from the Social Page: [quote]Anyway back to the start up. Very slow to engage reverse, just sat there until pumped up to pressure I guess. I had noticed this lack of action earlier this fall after the car had sat for a stretch of time. This time I checked the transmission dipstick before starting the engine, and found the fluid to be way high. I’m going to repost this transmission segment over on the Transmission & Rearend page.[/quote] I had this bad boy (904) out of the car this spring, say 2000 miles ago, installed a new Valve Body, adjusted the bands, new filter and pan gasket, new torque converter & seal. No external leaks. After reading the FM Transmission Service Diagnosis page heading, “Delayed Engagementâ€, I have ruled out the following: Low fluid level, reads full when warmed up Incorrect gearshift linkage, as no delay when car is driven several times a week on cold start. What has to be examined is: Valve Body leakage. Faulty oil pump. Questions: Accumulator apart 2000 miles ago, new valve body with shift kit called for spring removal, and there were no rings installed on accumulator piston when I opened her up. Should I have installed new rings? After car is at operating temperature there has always been a slight fluttering, or shuddering under acceleration. Could this be a result of the accumulator passing fluid due to missing rings? Someone suggested that this was caused by the 2600 stall converter, sounds fishy to me. No fluttering when fluid is cold. No hydraulic pressure tests have been performed, could the shuddering be a result of too low pressure? Dose the oil pump have a foot valve that prevents drain-back when car is not running? The high fluid level must be caused by the torque converter draining back to the pan after extended down time. I’m not clear as to how the internal fluid flow is controlled when car is off. |
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| Author: | Joshie225 [ Sat Jan 09, 2010 12:33 pm ] |
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Yes, you are suffering from torque converter drain back. The hydraulics are working fine, but you don't get any power transfer until the torque converter fills up. Some shift kits give you lubrication oil flow and torque converter fill in park, but not all and none from the factory. This is why you are instructed to check the fluid level in neutral. The only way to fix the drain-back is a new front pump bushing and seal. Even then it might not last long if the transmission isn't well aligned with the crankshaft. I can't comment on the shuddering other than to say you should have sealing rings on the accumulator. Bummer it was put back together without them, twice. |
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| Author: | SlantSixDan [ Sat Jan 09, 2010 1:49 pm ] |
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This is just an annoyance, not a problem that will cause damage to the transmission. You can put off doing anything about this non-critical situation for a long time (at least until the weather's warm) by shifting out of Park and into Neutral before you start up the car first thing in the morning. By the time you've fastened your seat belt, turned on the radio, adjusted the mirror and all that, the torque converter will have filled up and Reverse engagement should be much more immediate. Be sure your handbrake works or get into the habit of putting your foot firmly on the brake pedal if you do it this way. You may want to install a TransGo #SK-TFSC kit, which will not radically alter the shifting but will permit torque converter flow in Park and make a few other improvements. |
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| Author: | wjajr [ Sat Jan 09, 2010 5:40 pm ] |
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Thanks guy for a quick response. Josh: [quote]The only way to fix the drain-back is a new front pump bushing and seal. Even then it might not last long if the transmission isn't well aligned with the crankshaft.[/quote] I did replace the front pump seal, if that is the one that the nose of the torque converter impales on the bell housing side of the input shaft. The old converter that was removed was a flopping mess. So that bushing may be beat. I suspect the front pump bushing, or is it called the “Input Shaft Pilot Bushing†will require disassembly of the transmission, or can it be removed from the bell housing side on the bench? How dose one know if the transmission is properly aligned? When I installed the transmission it lined up easly, and the flexplate bolts started without any problem. As for the accumulator rings, I was not able to locate just the rings for that device. If I can find just the sealing rings I wouldn’t mind dropping the pan this spring for a little fixen, and toss in Dan’s TransGo #Sk-TFSC kit at the same time. Dan: [quote] You can put off doing anything about this non-critical situation for a long time (at least until the weather's warm) [/quote] LOL After tomorrow’s trip, a high of 16* predicted, this car ain’t moving until the end of mud season…That is when all snow, salt, and melt water have gone from all road surfaces which will be around mid April here in Maine. I'm happy that this drain down condition is not catastrophic. |
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| Author: | Joshie225 [ Sat Jan 09, 2010 7:42 pm ] |
| Post subject: | |
The front pump bushing requires removing the pump from the case and then (if memory serves) splitting the pump to drive the bushing out. If you can get someone to sell you a used accumulator you might be able to get it with the rings on it. Ask a trans shop where they buy hard parts around there if you don't already know. |
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| Author: | Terry Geer [ Sun Jan 10, 2010 8:45 pm ] |
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I am still a little concerned about the fluttering or shuddering. The trans has a planetary gearset, which requires one of the three pieces to be driven, and one to be held. If the drive/forward clutch is slipping. the rpm should flare, clutch material and burnt fluid should be in the pan. The holding device is a sprag (similar to a ratchet; locks one way, free-wheels the other). I don't think fluid temp should really effect a worn sprag. And a sprag should make lots of ugly noise. There is also a sprag/overrun cluth in the torque converter for vortex vs rotary flow/ accelerate vs cruise. Again, a bad one should make noise. A worn pump bushing may contribute to low line psi and loss of clamping force, which I guess could be most effected by fluid temp. If you are brave, I would go for a stall test (power brake): with the engine idling, parking brake on. foot brake on, bury the loud pedal. ONLY FOR A FEW/ MAYBE FIVE SECS! Watch the tach. If rpm flares higher than stall, you have slippage inside the trans. If there are ugly ratcheting sounds, you have a bad sprag. We can do this in D range, L1 range, and R. DO NOT DO THIS IN THE GARAGE IN FRONT OF MAMA'S DRYER! Does the shudder occur in both D and L1-L2? Check that on a road test. In L1-L2 an extra band is used to help the sprag hold. Good luck, TG. |
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| Author: | wjajr [ Fri Jan 15, 2010 6:50 pm ] |
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Terry Geer: Quote: If you are brave, I would go for a stall test (power brake): with the engine idling, parking brake on. foot brake on, bury the loud pedal. ONLY FOR A FEW/ MAYBE FIVE SECS! Watch the tach. If rpm flares higher than stall, you have slippage inside the trans. If there are ugly ratcheting sounds, you have a bad sprag. We can do this in D range, L1 range, and R. DO NOT DO THIS IN THE GARAGE IN FRONT OF MAMA'S DRYER! Does the shudder occur in both D and L1-L2? Check that on a road test. In L1-L2 an extra band is used to help the sprag hold. Good luck, TG.
The shuttering is most noticeable after a 1-2 shift under light to moderate acceleration if memory serves. I don’t recall any shuttering during power braking, or tac jumping during power braking. The last time I drove the car was last week to move her to the new house, ambient temperature was 15 degrees, and the temperature gage hardly made it off of the first mark in the warm zone… I didn’t recall any shuddering during the trip, and I suspect the transmission never really warmed up to full operating temperature as I have a cooler, and finned deep pan. This shuddering condition is more pronounced during warm weather when put-putting around town. The car is mothballed until mid April when the roads become dry & salt free. |
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