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Old 10-08-2010, 06:51 AM
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New cam..same transmission problems

I had posted a few months ago,in the engine forum, looking advice to correct a badly mismatched SBC 350 combination.A 327/350hp cam had been installed in a 7.5:1cr engine.Followed the advice given and now have installed a rv cam(Melling MTC-1).The engine runs great now,smooth idle,pulls the old truck quite well.

Now I am questioning my stock TH350 transmission.My complaints before was that you couldn't pull the trans into gear w/o it stalling unless the idle was up around 950,then drop to 650 or 700 causing BS driving conditions.Wicked clunk on the rear end/ujoints putting it into gear.And having to drive with both feet!Everyone seemed to have the same opinion that the lopey cam was the culprit with a stock converter.

So,new cam,engine idles nice but still same drive issues..do I have converter/transmission problems after all?It acts like the converter is at or near stall speed at an idle.It does whine a bit,but goes down the road fine upshifting/downshifting.
Any suggestions as to where I look next?

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Old 10-08-2010, 09:19 PM
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trans prob

Sounds like the t converter won't unlock at idle, the trans shouldn't whine though, so I would look at replacing the trans and converter. Go with a bit of stall on the converter about 2500 is a good stall for normal street use.
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Old 10-08-2010, 10:06 PM
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I dont think he has a TH350C Trans, so no Lockup Clutch.
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Old 10-08-2010, 10:12 PM
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All auto trans unlock or slip a bit at idle, a normal converter locks up just off idle, the main thing it also whines so the trans definetily has a prob.
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Old 10-08-2010, 10:51 PM
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You are talking about Stall Speed, not Lockup. Yes, they do start to Multiply Torque as rpm increases and Couple at higher rpm but, unless they have a TCC/TorqueConverterClutch they don't Lockup at 1 to 1 ratio. Like a Th350C, 2004R, 700R4 Trans etc..
He has installed an mild RV Cam which shouldn't cause a problem with creeping in gear or stalling the engine. May need a little more Initial timing advance, Idle speed & Idle mixture adjustment etc..
I agree the wining is either a TC or Pump problem. Maybe the TC has a Stator problem causing a very low rpm stall condition.
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Old 10-09-2010, 04:50 AM
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I'm not too hung up on the whine.It's not loud, constant at idle or increases with rpms.More of a gear or tire whine that increases with speed and drops back at shifts,then increases again.But the creeping/stalling has me confused.

As far as the tune I feel its pretty good.Timed at 14deg initial,36 total w/vac adv hooked to full manifold vac.Runs good,real clean idle..doesn't burn your eyes,or smell like gas running out the pipes.Tried increasing initial,no change other than the fact it wouldn't crank.

I was hoping some of you might have run into this before and save me a trip to trans shop.The only thing I can think of is if GM used different converters over the years and someone has installed the wrong converter. I'm sure this trans/converter has been changed because the speedometer is off by 10mph.
If not the converter causing this could an improperly installed shift kit or transmission problem cause full fluid pressure at idle and make it act this way?
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Old 10-09-2010, 06:45 AM
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The whine from the trans indicates a problem.. high pressure, clogged filter , wrong gear clearance setup in the pump.

high pressure will not cause a converter to stall an engine. If the converter is ballooned from high pressure, that can cause problems internally on the converter operation. A ballooned converter can cause damage to the engine crank shaft and the trans pump

GM built many different converter stall ratings for the trans. A proper setup converter will not stall the engine with a mild camshaft you say is in the engine now.

You indicate the engine setup - tune is fine, so the problem in my view is the converter. It sounds like the trans needs attention too.
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Old 10-09-2010, 07:11 AM
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Have you tried ported vacuum to the dist. instead of full manifold?
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Old 10-09-2010, 08:43 AM
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I had tried the ported vac option just to see if the drop in idle/vac might be changing timing causing this.Not much diff.
I think I'll just spend a couple hours and drop in a new converter to see what happens.If I end up having to r&r the transmission at least I'll already have a new converter.
Thanks for the help
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