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727 Torqueflite issue #3090614
10/31/22 08:25 AM
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Hoping to get some direction from some members with more experience with this than I. I recently acquired a '78 D150 with a mild 360 that I have been sorting out. When I got it, it had a Summit 650 with a totally mis-adjusted TV linkage. I don't believe it was run long this way, but it now has a TQ with properly set-up linkage. Fluid checks fine. It runs well and the trans shifts very well and at the right points, however.... Primarily when warm, I am getting a "bang" or "klunk" coming off idle such as when pulling away from a light. This does not occur all of the time, but enough to be concerned. The truck will start to move, and then the noise. It almost feels like it is slipping before engaging. I have been thru the driveline and all u-joints and rear are play free. It almost seems pressure related. I haven't touched the bands because it seems to shift and work so well otherwise. Any ideas where to look?

Re: 727 Torqueflite issue [Re: koak] #3090619
10/31/22 08:48 AM
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Does it also do this in manual low? If so I don't believe it's in the trans. When working at the Chevy dealer thiis was a common issue with pick-ups. The driveshaft slip yoke would stick on the trans output splines. It could be cured by cleaning the splines if dirty/rusty and lubing them.
Doug

Re: 727 Torqueflite issue [Re: dvw] #3090628
10/31/22 09:32 AM
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Thanks. I really don't believe it's there. I have experienced that in 4x's and have cleaned/ lubed them. This is a 2x and splines are clean free and no rust. Has a different feel too. They snap as you move. This moves then snaps or klunks. I'm not a trans expert, but I am wondering if a servo piston is losing pressure at idle or if there is something in the trans that could cause this. Doesn't feel/ sound like loose converter bolts either. I will have to try manual low and see if the symptoms change. I think the band applications are different in that case.

Last edited by koak; 10/31/22 09:35 AM.
Re: 727 Torqueflite issue [Re: koak] #3090674
10/31/22 12:05 PM
10/31/22 12:05 PM
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One piece driveshaft or two?

If two, check the center bearing for the same spline issue.

Only thing “on” in drive, standing still, shifter in D is then rear clutch and ORC.

The rear clutch may be partially on, then as you open the throttle the rise in line psi further applies the rear clutch.

That may be apparent with the ever popular but really used pressure test.

The ORC - possible something going on there but that could be eliminated by testing in manual low.

Last edited by Transman; 10/31/22 12:06 PM.
Re: 727 Torqueflite issue [Re: A727Tflite] #3090679
10/31/22 12:14 PM
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Thanks. Single piece driveshaft. There really is no spline, u joint or rear issue that I can find and I have looked. It really feels like something inside the trans engages as I apply throttle. The harder I apply throttle, the more pronounced the issue, but again it does not occur all of the time. More often when warmed up. Truck will start to roll, but doesn't feel positive until the dreaded klunk. I've become accustomed to feathering it off throttle, but have not tried manual low. I'll do that and will do whatever kind of test is needed to troubleshoot, just don't know where to begin Again, the trans works very well otherwise. So, starting in low will eliminate the ORC as an issue? I have read these can be damaged by abuse? I don't think the PO was kind to this rig in the short time he had it as evidenced by the rubber inside the wheel well...


Last edited by koak; 10/31/22 12:16 PM.
Re: 727 Torqueflite issue [Re: koak] #3090740
10/31/22 02:52 PM
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Originally Posted by koak
Thanks. Single piece driveshaft. There really is no spline, u joint or rear issue that I can find and I have looked. It really feels like something inside the trans engages as I apply throttle. The harder I apply throttle, the more pronounced the issue, but again it does not occur all of the time. More often when warmed up. Truck will start to roll, but doesn't feel positive until the dreaded klunk. I've become accustomed to feathering it off throttle, but have not tried manual low. I'll do that and will do whatever kind of test is needed to troubleshoot, just don't know where to begin Again, the trans works very well otherwise. So, starting in low will eliminate the ORC as an issue? I have read these can be damaged by abuse? I don't think the PO was kind to this rig in the short time he had it as evidenced by the rubber inside the wheel well...



Manual low application will lock the rear drum, just as the ORC does. So if that fixes it, that’s a possibility.

Other quick test that may help, lock the the throttle pressure lever all the way back. That will raise line. If that helps, then sounds like a leak in rear clutch apply.

Re: 727 Torqueflite issue [Re: A727Tflite] #3090750
10/31/22 03:10 PM
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ok. Thanks. Will try those. It did take me a bit to get the TV adjusted right. In fact right now the lever is just off the fwd stop to get full rearward motion at wot. I did have some flare on 2-3 at very light throttle and early shift points with that lever just a bit further fwd.

Re: 727 Torqueflite issue [Re: koak] #3090769
10/31/22 04:05 PM
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Originally Posted by koak
ok. Thanks. Will try those. It did take me a bit to get the TV adjusted right. In fact right now the lever is just off the fwd stop to get full rearward motion at wot. I did have some flare on 2-3 at very light throttle and early shift points with that lever just a bit further fwd.


You don’t have to “adjust” it, just use something to hold it back all the way, like a rubber band or some thing. Just a test.

Last edited by Transman; 10/31/22 04:05 PM.
Re: 727 Torqueflite issue [Re: A727Tflite] #3090770
10/31/22 04:21 PM
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Yes, I understand that. Was just saying how sensitive that adjustment seemed to be, but its been a while since I had to play with one. Don't recall how normal that was.

Re: 727 Torqueflite issue [Re: koak] #3091466
11/03/22 06:29 PM
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Ok, Had a chance to do those couple tests. The results were not what I expected. I can report:

1.) This condition does not happen until the truck is fully warmed up, like 10 min.
2.) Starting in Low or first had no effect. Still had the "slippage" and klunk
3.) Reverse does not show this problem
4.) Rigging TV lever fully back had no effect other than raising my idle speed a bit.
5.) It is more pronounced when starting up an incline. It seems to always do it then.

Any further ideas? Maybe at this point gotta drop the pan. Maybe I'll see something then. Again, aside from this, it operates as it should. The fluid looks and smells fine although it was maybe a full quart and a half low in addition to the misadjusted TV when I got it. The PO really didn't do it any favors. Thanks for your help.

Re: 727 Torqueflite issue [Re: koak] #3091478
11/03/22 08:02 PM
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If it’s in the trans my best guess is hard parts related to the rear clutch. Could still be an ORC issue but can’t say I have ever seen this before the way you describe it.

Re: 727 Torqueflite issue [Re: A727Tflite] #3091488
11/03/22 08:56 PM
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So, you are thinking hard parts as opposed to a seal? Trying to think of how I could further troubleshoot this. Maybe I'll pull the shaft and look at the rear backlash independently, but I just don't see it. It definitely comes with heat (time). No rear noise or trans pump whine either. Is it true you can check the sprag by turning the rear yolk in both directions and it should be tougher to turn in one direction? Would a clogged filter act this way at all? Maybe I'm grasping here, but pulling the trans is not something in my immediate plans unless absolutely necessary. Thanks.

Re: 727 Torqueflite issue [Re: koak] #3091491
11/03/22 09:14 PM
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Originally Posted by koak
So, you are thinking hard parts as opposed to a seal? Trying to think of how I could further troubleshoot this. Maybe I'll pull the shaft and look at the rear backlash independently, but I just don't see it. It definitely comes with heat (time). No rear noise or trans pump whine either. Is it true you can check the sprag by turning the rear yolk in both directions and it should be tougher to turn in one direction? Would a clogged filter act this way at all? Maybe I'm grasping here, but pulling the trans is not something in my immediate plans unless absolutely necessary. Thanks.


If you had a gauge on it the line pressure should have risen when you brought the TV lever back. That “should” have helped things if the rear clutch seal was at fault but you never know. If a seal was bad I would expect some slip or chatter even when warmed up. Dropping the valve body and doing an air pressure test may reveal something.

Last edited by Transman; 11/03/22 09:15 PM.
Re: 727 Torqueflite issue [Re: A727Tflite] #3091519
11/03/22 10:50 PM
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I was waiting for your results before posting this but I had a bad converter do this.

Re: 727 Torqueflite issue [Re: B1MAXX] #3091555
11/04/22 08:22 AM
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Originally Posted by B1MAXX
I was waiting for your results before posting this but I had a bad converter do this.


If it was in the converter, wouldn't it do it in reverse as well? And your converter did this only when warm?

Re: 727 Torqueflite issue [Re: koak] #3091556
11/04/22 08:37 AM
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Originally Posted by koak
ok. It did take me a bit to get the TV adjusted right. In fact right now the lever is just off the fwd stop to get full rearward motion at wot. I did have some flare on 2-3 at very light throttle and early shift points with that lever just a bit further fwd.


Just seeing this you don't have the TV adjusted correctly if it is like this , but this misadjustment isn't the cause of your problem.


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Re: 727 Torqueflite issue [Re: koak] #3091557
11/04/22 08:42 AM
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Originally Posted by koak
Hoping to get some direction from some members with more experience with this than I. I recently acquired a '78 D150 with a mild 360 that I have been sorting out. When I got it, it had a Summit 650 with a totally mis-adjusted TV linkage. I don't believe it was run long this way, but it now has a TQ with properly set-up linkage. Fluid checks fine. It runs well and the trans shifts very well and at the right points, however.... Primarily when warm, I am getting a "bang" or "klunk" coming off idle such as when pulling away from a light. This does not occur all of the time, but enough to be concerned. The truck will start to move, and then the noise. It almost feels like it is slipping before engaging. I have been thru the driveline and all u-joints and rear are play free. It almost seems pressure related. I haven't touched the bands because it seems to shift and work so well otherwise. Any ideas where to look?


This too ...
What do you mean by the rear being "play free " , that's impossible , there is backlash between the ring and pinion , if you truly have no backlash then something is not right with your rear axle. I had an 86 ramcharger and an 89 d150 and both had clunky rears but it mostly happened when first putting them in gear , it was the rear backlash opening up .

Transman is on to something when he says it sounds like HARD PARTS , I see a trans removal in your future .


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Re: 727 Torqueflite issue [Re: JohnRR] #3091558
11/04/22 08:46 AM
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That is the best can adjust the TV. Having the lever just off the fwd stop (probably no morethan .25) is the only way I could get full travel rearward at WOT. And that last adjustment to obtain full travel made a big difference in shift points and kd. All factory parts, but not sure if the levers are matched, or if there were different ratios.
And yes, there is a small amount of lash at the rear, but nothing that would account for this condition.

Last edited by koak; 11/04/22 08:49 AM.
Re: 727 Torqueflite issue [Re: koak] #3091562
11/04/22 08:54 AM
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What I recall was after "it" happened the truck was still driveable but the converter felt tighter but not efficient. It did it the first time pulling out from a stop on hill. And as I recall it was bad at all conditions hot cold ,front/backwards. It wasn't like that long. I replaced it that week after getting home. The initial clunk wasn't a slight clunk either. My main reason for putting this post out here was when I read your situation the first thing I though off was that converter failure I had. But these guys responding know more than me. That's why I waited until their diagnosis was complete.

Just add, if it isn't tranny, converter, then it would have to be driveline or chassis.

Last edited by B1MAXX; 11/04/22 08:56 AM.
Re: 727 Torqueflite issue [Re: koak] #3091563
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Originally Posted by koak
That is the best can adjust the TV. Having the lever just off the fwd stop (probably no morethan .25) is the only way I could get full travel rearward at WOT. And that last adjustment to obtain full travel made a big difference in shift points and kd. All factory parts, but not sure if the levers are matched, or if there were different ratios.
And yes, there is a small amount of lash at the rear, but nothing that would account for this condition.


Then you don't have the right TV parts, .25 is a 1/4 " that's actually off a lot and the fact that when you put it to wide open and it raised you idle tells me it's not adjusted properly .

Can you post a picture of the linkage at the carb at idle ?


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