clunk into reverse or drive

[flyboy1100]

No piles of metal chunks or mud puddles in the bottom of the pan? Not even a small mud puddle, like about the size of a quarter?

And you're sure this whining is actually whining and not more of howeling? Can you tell yet where it's coming from. Front of the truck or rear?

You know somtimes when I get a weird noise going on in my truck, I try to get on the freeway and get close to the center divider wall. You like being in a construction zone? Notice how the noises are more profound and you can actually get an idea of where they're at as far as front or rear.

So many times I hear people complain about front brake squeal and quite often it's actually the rear brakes and nothing more than excessive brake dust. Take the damn drum off, tap tap on the concrete with the drum, spray brake clean on the shoes and springs with a piece of cardboard underneath to catch the drips, install drum, noise gone.

There was some "mud", mostly on the magnet. But who knows the last time the fluid was changed, could of been 10-15yrs ago! Truck sat for at least 5, maybe 6 years before my cousin bought it last year. He only had it for 8 months before I bought it, he just drove it.....

No idea of the rear end other than 3.42 gearing. Without pulling the cover, is there any way to tell?

1U joint on the front is shot for sure, I dont have tall enough Jack stands to get the rear wheels off the ground to check the rear joints. My guess is they are due.

Will be installing a tach soon, can I use that to help with shift points? It is for sure too soft now, because even trying to get it to kickdown wasn't working. But with the cable a few clicks back on my first test drive today it shifted really hard 1-2, hard enough to squak the tires...



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[flyboy1100]

There was some "mud", mostly on the magnet. But who knows the last time the fluid was changed, could of been 10-15yrs ago! Truck sat for at least 5, maybe 6 years before my cousin bought it last year. He only had it for 8 months before I bought it, he just drove it.....

No idea of the rear end other than 3.42 gearing. Without pulling the cover, is there any way to tell?

1U joint on the front is shot for sure, I dont have tall enough Jack stands to get the rear wheels off the ground to check the rear joints. My guess is they are due. Also needs tires, but the whine stops when throttle is reduced and i can still hear the noise. I think it is coming from under the cab or in front, I dont think I hear it from the rear.

Will be installing a tach soon, can I use that to help with shift points? It is for sure too soft now, because even trying to get it to kickdown wasn't working. But with the cable a few clicks back on my first test drive today it shifted really hard 1-2, hard enough to squak the tires...



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[350runner]

You just want a nice firm shift not like a brick. So if you have that now with no flash in rpms between gears that sounds good. Thing you really don't want is the trans shifting really quick. If your first shift is @15 mph then the second should be@ 35 or approx. It's this what you are experiencing?

Sent from the dust in front of you!

 

[HotRodPC]

I did forget about the magnet on a 700r4, usually on a Th350 there is a spot where you get a pile of mud about the size of quarter, and there would be too on a 700r4 if it didn't move to the magnet which is perfectly normal. That's just the normal wear as long as it's a small amount and most people go into a panic attack thinking their transmission is trash.

 

[flyboy1100]

I did forget about the magnet on a 700r4, usually on a Th350 there is a spot where you get a pile of mud about the size of quarter, and there would be too on a 700r4 if it didn't move to the magnet which is perfectly normal. That's just the normal wear as long as it's a small amount and most people go into a panic attack thinking their transmission is trash.

Ya, nothing large, just normal amounts of wear imho.

I'm not sure what transmission is on my dad's 98 1500 w/ 350, but his drive shaft only moves 1/8-1/4 of a turn when putting it in gear. No obvious clunk either. So it makes me kinda wonder what is causing it on mine



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[flyboy1100]

Does my 700r4 have an electronic pressure control? Kinda sounds like my problem.
http://m.blazerforum.com/forum/showthread.php?t=53410&styleid=5

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[HotRodPC]

If you know for a fact a U joint is bad, that's all it takes to get a clunk. Don't forget, a driveshaft is like a large hollow echo chamber so any noise attached to it is going to be amplified. Then of course you have this 1/4 to 1/2 turn of play. I think I may have mentioned it already, depending if you have an open diff, or what locker or LSD unit you may have, this could be normal. If you know it's an open differential, then it's to much for sure and is with MOST LSD units also. Detroit Locker and I'd imagine Yukon Locker since they're very similar are the only ones I know that allow that much play. And it's really not play. It's the amount of play between both axles and the play within the ring and pinion, but it will FEEL like alot and APPEAR to be alot more gear lash than it really is.

Another question, is this play your talking about, is this with the trans in Park and the wheels off the ground? Or wheels up or what? Explain that as to how you're doing this play test. Something we all may be overlooking is your transfer case. I'm wondering if you might have excessive chain slop that can be causing your clunk?

 

[HotRodPC]

Does my 700r4 have an electronic pressure control? Kinda sounds like my problem.
http://m.blazerforum.com/forum/showthread.php?t=53410&styleid=5

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The only thing you will have that is electronic is your Converter Lock Up. If it's a 90-92 (or is it 89 or 91, **** I forget now) model then you'd have an electronic speedo too. But that's it. Even on an 87 up with a TBI ECM, the manual cable driven speedo uses a converter from the speedo to send signal to the ECM. So this is NOT likely your problem.

That's a pretty informative link by the way. Even though it pertains much more to 4L60-E IMO.

 

[HotRodPC]

Something else I just noticed and thought of, yours is an 86 right? You know in 87 up there were several changes made to the 700r4, as there was every single year. But 87 was the biggest change by adding the auxillary valve body. This did things like added an abuse valve, for quicker shifts from D to R, R to D and D to R as if to be rocking a vehicle when it was stuck. Another improvement was to make smoother, what they call "Garage Shifts". As in going from P to R, or R to D at slow speeds and get rid of the occasional harshness and clunk. So again, you might have this issue and it's just normal for your transmission being it's an 86 model wo the auxiliary valve body. Again, if you have a stiffer shift from P to R or D, or R to D, D to R or whatever, and you have an ailing U Joint, excessive ring and pinion lash or sloppy Tcase chain, this is going to be made more profound by the harsher garage shifts. I think I'd really consider replacing the U Joints, at least the one you know is bad, and take it from there.

 

[flyboy1100]

If you know for a fact a U joint is bad, that's all it takes to get a clunk. Don't forget, a driveshaft is like a large hollow echo chamber so any noise attached to it is going to be amplified. Then of course you have this 1/4 to 1/2 turn of play. I think I may have mentioned it already, depending if you have an open diff, or what locker or LSD unit you may have, this could be normal. If you know it's an open differential, then it's to much for sure and is with MOST LSD units also. Detroit Locker and I'd imagine Yukon Locker since they're very similar are the only ones I know that allow that much play. And it's really not play. It's the amount of play between both axles and the play within the ring and pinion, but it will FEEL like alot and APPEAR to be alot more gear lash than it really is.

Another question, is this play your talking about, is this with the trans in Park and the wheels off the ground? Or wheels up or what? Explain that as to how you're doing this play test. Something we all may be overlooking is your transfer case. I'm wondering if you might have excessive chain slop that can be causing your clunk?

Wheels on the ground, I might try lifting the rear end and see what the wheels do.

Is there any way to tell what I have in the rear end w/o pulling the cover? Not a bad idea to change the fluid, but not on my list quite yet. Will do the u joints first.

There is also a hose that comes off the rear end it looks plugged, what is that for?



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[HotRodPC]

The plugged hose is the case vent. Should be bolted to the bottom of the bed keeping it up high as possible so you don't get water in it.

There are some tell tale signs of what's in an axle housing but it's not fool proof. We can figure out what gear ratio you have. We can also know if it's a locker or some LSD units by the way the wheels spin. With both wheels off the ground, if they both spin the same direction it can be a spool (highly unlikely) locker or some LSD units. If it the spin opposite it's probably an open peg legger differential, but could be some locking or LSD units also.

Wheel on the ground, with the transmission in Park or N?

 

[flyboy1100]

The plugged hose is the case vent. Should be bolted to the bottom of the bed keeping it up high as possible so you don't get water in it.

There are some tell tale signs of what's in an axle housing but it's not fool proof. We can figure out what gear ratio you have. We can also know if it's a locker or some LSD units by the way the wheels spin. With both wheels off the ground, if they both spin the same direction it can be a spool (highly unlikely) locker or some LSD units. If it the spin opposite it's probably an open peg legger differential, but could be some locking or LSD units also.

Wheel on the ground, with the transmission in Park or N?

Should be 3.42 unless both diffs were changed from the rpo codes.

I will try to get the back jacked up tomorrow night or Monday afternoon. And report back.

Brw, the worn/stretched chain in the np208 seems likely for this clunk? I will lock the hubs and try 4h and see if there is a difference in the clunk, not sure if it will tell anything, but it's worth a try.

Clunk happens from P or N, or going from R to OD (really any forward gear) but once in gear there is no additional clunk from OD down to 1 or vice versa.all tests with wheels on ground

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[MadOgre]

NOPE your TV cable is not adjusted correct if you get that hard shift from 1-2.

I just got mine adjusted correctly today after 2 weeks of messing with the adjustment.

Adjust it from the carburetor, at WOT the cable should be taught. Mine was relatively taught so I was thinking what the hell is going on ? But the guys at GM say it should be very taught so I took the cable out of the bracket with out moving the adjustment on it and I counted how many ratchet grooves were exposed and I moved the slider in one notch the equivalent of 1mm. It took a while and I was glad I counted the notches first otherwise I would a been screwed trying to get it right. Damn thing shifts beautiful. Every gear shifts EXACTLY the same. Each shift is quick and pronounced but not harsh at all. And it has the least amount of clunking into gear that I have ever had. It also accelerates better in first gear than it ever has.

I also had the harsh 1-2 shift but not bad in the rest. Now I don't.

 

[flyboy1100]

NOPE your TV cable is not adjusted correct if you get that hard shift from 1-2.

I just got mine adjusted correctly today after 2 weeks of messing with the adjustment.

Adjust it from the carburetor, at WOT the cable should be taught. Mine was relatively taught so I was thinking what the hell is going on ? But the guys at GM say it should be very taught so I took the cable out of the bracket with out moving the adjustment on it and I counted how many ratchet grooves were exposed and I moved the slider in one notch the equivalent of 1mm. It took a while and I was glad I counted the notches first otherwise I would a been screwed trying to get it right. Damn thing shifts beautiful. Every gear shifts EXACTLY the same. Each shift is quick and pronounced but not harsh at all. And it has the least amount of clunking into gear that I have ever had. It also accelerates better in first gear than it ever has.

I also had the harsh 1-2 shift but not bad in the rest. Now I don't.

Good to know, I will play with that some more. I know I will be different, but how many clicks are you at? Mine is around 5iirc

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[MadOgre]

I counted 12 but moved it to 11 but im using a stock GM cable and a TCI bracket for qaudrajets.

Its crazy that 1mm would have that much of an impact. Just goes to show the need to have these cables adjusted correctly.