Clunk noise when shifting upwards

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Skeeter007

Skeeter007

Skeeter007
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I'm having the same problem and this thread talks about it and yet no solution is found. I have quoted his problem and mine.

1971 Scamp /6

Quote from : http://www.forabodiesonly.com/mopar/showthread.php?p=424584

" Just to give some more details, it acts fine when putting into gear and never misses a shift or slips. The shifts are also pretty firm and quick at WOT. The only issue I have with this transmission is that when accelerating slowly and then gradually letting off the gas(forgot to add that part), for example when driving through a full parking lot with a stop at the end, it will most of the time "clunk" into second gear as I start to coast. If I am accelerating at a constant rate, no matter how slowly, it usually won't "clunk" like that."

My build and discussion: http://www.forabodiesonly.com/mopar/showthread.php?t=273991

Any thoughts? I will check the U joint tomorrow weather permitting.
 
In my own oppinion this is caused by line pressure being higher from an open throttle, and then when you back off the throttle the trans suddenly reacts and it shifts. (Bam)
As far a I ever new it was an unfortunate side effect of design, and there is nothing you can do about it without making the trans work terrible in other ways.

I do have some history in the field, so it's not just a random guess.
 
when all else checked pull the rearend open it will tell you a story
 

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Absolutely normal, as a matter of fact I normally pull mine in manual low in slow stop and go traffic or parking lots just to keep it from having the harsh back-out upshift.Every one I've ever driven does it.
 
Well I guess after I run through all the checks and if it remains the same I'll have a manual automatic transmission. Lol. Just don't want to hurt it as I need the summer with it and maybe a little into next season before I slip the other toys under her.

Posted via Topify using iPhone/iPad
 
Does your car have a shift improver kit installed? A lot of shift improver kits cause it because they raise the line pressure. It won't hurt much. Little hard on U-joints but that's about it. What's happening is when you let off the gas the 1-2 shift hits taking up the slack in the drivetrain. If you back off the throttle pressure linkage adjustment a little it should help some. The only drawback to that is you may lose kickdown at highway speeds.
 
I wouldn't even know where to look at this point. This car is a learning curve for me. I'm tackling the problems head on and hopefully by the fall I can start to sort out and plan the conversion 440/727/8.75 but until then I'd like to keep driving it reliably possibly into next summer if I'm hit with delays. I sure do get a lot of comments though on the street.

Posted via Topify using iPhone/iPad
 
The clunking noise you are experiencing is from a bad u-joint or joints or rear end slop is excessive.
They didn't do this when new, so why now?
Your question will be answered when you check both out compared to factory specs.
I'll bet it's a bit of both.
 
TrailBeast said:
Dartnut said:
They didn't do this when new, so why now?
QUOTE]
Yes they did as matter of fact.

You may be misunderstanding the symtoms described.
Click to expand...

What i was eluding to was to look at the FSM and set the car up to specs, eliminating the obvious.
It might be a line pressure problem in the trans, but my best bet is on the u-joints or slop in the rear end gears.
And NO they didn't make clunking sounds like this when new especially under these circumstances........
Click to expand...
 
Dartnut said:
TrailBeast said:
What i was eluding to was to look at the FSM and set the car up to specs, eliminating the obvious.
It might be a line pressure problem in the trans, but my best bet is on the u-joints or slop in the rear end gears.
And NO they didn't make clunking sounds like this when new especially under these circumstances........
Click to expand...

Ok
Click to expand...
 
Dartnut said:
The clunking noise you are experiencing is from a bad u-joint or joints or rear end slop is excessive.
They didn't do this when new, so why now?
Your question will be answered when you check both out compared to factory specs.
I'll bet it's a bit of both.
Click to expand...

You might be correct on something being worn but I have seen a few do it right from the factory when things were tight. One I remember real well is back in the early 80's a buddy of mine had a 78 Diplomat that did it. It also engaged into reverse hard. My only guesses are the pressure regulator got cranked up too high, and/or the accumulator spring was broken or left out. Something else that I already mentioned is if it has a shift improver kit installed a clunk like that can happen because even a tight drivetrain has a little slop in it. If the trans shifts real firm into 2nd and it happens right when he lets off the gas that little bit of slop can sure make a heck of a clunk. The OP doesn't seem to know if it has a shift kit or not by what I read.

Just my .02
 
Its an upshift with no throttle pressure. The clunk is not the trans, its most likely a ujoint or slop in the rearend.
 
I pulled the wheels and took a look at the brakes and they are solid with even wear and seem to have been done recently. When I had the car up and this may mean nothing as I'm not familiar with this rear end, but when rotating the axle left to right there seems to be play before the drive shaft would begin to spin. Maybe nothing but worth mentioning. I'll be back at it tomorrow and will definitely inspect the u joints a little closer.

Posted via Topify using iPhone/iPad
 
PoisonDart74 said:
Let r' clunk!
Click to expand...

Crank that pressure up so it barks the tires instead of clunking. :toothy7:

Oh by the way Dartnut, I think I misunderstood not you.
They all have a definite thump under certain throttle openings and zero load sudden upshifts, but the clunk maybe not so much depending on what "clunk" means to each person.

You could have been and very possibly are right about clearances in gears.

Now if the OP would have said "clang" then I'd say ujoints.
 
Skeeter007 said:
I pulled the wheels and took a look at the brakes and they are solid with even wear and seem to have been done recently. When I had the car up and this may mean nothing as I'm not familiar with this rear end, but when rotating the axle left to right there seems to be play before the drive shaft would begin to spin. Maybe nothing but worth mentioning. I'll be back at it tomorrow and will definitely inspect the u joints a little closer.

Posted via Topify using iPhone/iPad
Click to expand...

There's backlash (clearance) between the ring and pinion that is normal. It shouldn't be much (.006"~.010") but if it's at the top end of the scale you can easily see the play your describing. It's possible it's excessive. To know for sure you have to put a dial indicator on it and measure it.
 
I'm having the same problem. Getting the clunk/ bang Doesn't do it when I'm shifting at high rpm but defiantly when just cruising.

I noticed that I can grab my drive shaft when the cars in neutral and rotate the drive shaft about a half inch in either direction.
Not trying to high jack this thread but thought I'd chime in.
 
It doesn't sound too serious. Probably more of an annoyance than anything. If it doesn't turn out to be something simple and obvious (ie U-joints), then just let it ride. I'm sure it will hold together unti you are ready to do the drivetrain swap.

But, that being said, I am very interested in finding out what is causing the clunking sound. Hopefully you are at least able to diagnose it, if not repair it.

Good luck Brandon and keep us updated!
 
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