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Transmission problem, I think

I have a 72 Chev with a 350 engine, 350 trans. I bought it at least 10 yrs ago. When I accelerate hard from a stop, I feel this scary shuddering coming from somewhere. I have replaced the motor and trans mounts that weren't too good. No difference. I replaced a noisy u-joint and center bearing. No difference. I decided to just drive the thing until it tells me what is wrong by other symptoms or a failure. Not too smart you might think but it seemed logical at the time. 10 years later, it is still doing the same thing and yet it keeps working otherwise. Well it's time to replace the motor and I wonder if I should also do something about the shuddering. Is this a symptom of a known transmission problem? Am I headed for a trans failure? Anything a backyard guy can check or replace to figure this out? I am not much of a transmission guy but as fast learner. I was thinking if this old TH350 needs replaced, I would rather convert to an overdrive type instead, just to save on gas. The present 8-10 mpg at $2.00 per gallon makes me want to be driving a toyota except this old chev and me have been a team for too many years. Any trans guys out there that can help out an old, sentimental fool? Thanks in advance

Reply to
William G.
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William...you need to elaborate more about what kind of vehicle it is. Put yourself in our shoes trying to detrmine what kind of 72 Chev your'e talking about........see what I'm saying?

Reply to
Mad Dog

Check the flywheel for cracks (might as well replace it for the price of a magnaflux these days), and replace the harmonic balancer for starts..............Also, if it's a posi rear, pop the cover and see if the clutches are worn out. I'd say it might be your clutches or frictions in the transmission but after ten years it would have puked it's guts out if that was it. Regardless, drain the pan, replace the filter and refill with new ATF and see if that helps.

Doc

Reply to
"Doc"
72 Chevy 1/2 ton Fleetside 2WD, Custom Deluxe, rear leaf springs, power steering, no power brakes, no A/C, as far as I know a stock 350 4bbl, 3:73 gears. What else can I tell ya that might help?
Reply to
William G.

Thanks for the comments guys. I sent more info but here is some more: no posi rearend. Would harmonic balancer only do this from stop on hard acceleration? Thanks again. Bill

Reply to
William G.

Reply to
William G.

Another comment if it helps. I am pretty easy on the old girl. Goes back and forth to work daily but no serious hauling, maybe a trip to the landfill now and again, and no towing. The hard acceleration I am talking about is not the way I normally drive. Once in a while I need to step on it to pull out in busy traffic but, heck this is Idaho and there isn't much traffic, unless you live in Boise, which I don't. Just wondering if I could have nursed along a potential failure by just not demanding much performance. Would the clutches or other parts survive much longer than you might expect if I am a gentle driver? Or are they gonna puke no matter what? Bill

Reply to
William G.

Not usually, but if the balancer is only marginally shot, you'll feel the effects at high RPM only.

Doc

Reply to
"Doc"

If a clutch or friction was going out on the AT 10 years ago, no matter how nice you drove it, it would have puked by now. One possibility is that the fluid is shot and the clutches are slipping on hard acceleration. I'd drain the pan, change the filter and add one bottle of Lucas Transmission Fix (great stuff!) when you refill. The Lucas is thicker than snot, so I'd recommend adding it directly to the pan before you put it back on.

If you're cruising at 55-60 mph in 3rd and you mash it, getting it to kick down into second and popping the RPM's way up there, do you get the same shudder?

Doc

Doc

Reply to
"Doc"

Thanx william, the u-joints may be out of phase now and before you disassembled the driveshaft. But it sounds more like the crankshaft is bouncing around in the main journals due to some worn out bearings, It would cause some shuddering on hard acceleration but run fairly smooth in cruise mode. Do an oil change and listen to the motor on restart before oil pressure builds in the new filter....every sound tells a story.

Reply to
Mad Dog

Damn, Doc, where you been hiding? I haven't seen ya around here in a while.

Cheers, Kyle

Reply to
KB

Interesting analysis but adds to my dilemma. I plan on installing the new motor and if the shudder is main bearings, the problem will be fixed. On the other hand, I will have the transmission in a position to have it fixed or replaced. If I plop in the new motor and it still shudders, I need to do more work to take out the trans. Since I am a lazy bastard, and don't want to do more work than I have to......what to do, what to do...??? Maybe I should bite the bullet and take it to a trans shop to have it checked out anyway as long as it can easily be put on the ground. That would give me a better shot at reliable transportation, motor and trans, but will definitely cut into my beer money. Thanks for the suggestions. I shows you gave it some thought and I appreciate it. Bill

Reply to
William G.

He he he, been busy at work and home man, haven't had much time to keep up with the ng. Things are lightening up a bit now so I should be around a bit more.......................

Doc

Reply to
"Doc"

Had an old 67 long bed that did the same thing. Same set-up, 350 / 350. Thought it was the crappy two piece drive shaft, but problem still existed after rebuilding and balancing shaft. Turned out to be the torque convertor. Ran fine until you stood on it. Would rattle the doors. Replaced convertor with a cheapie rebuilt unit, and problem vanished.

Reply to
Bill W

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