Guest Posted August 28, 2006 Share Posted August 28, 2006 I put a new small block in my 72 MC over the weekend with sportsman II heads and .460 lift cam with a .232 duration, based on the cam specs I decided to put a 2500 stall converter in it. I got it running this weekend, filled the transmission (TH350) warm in park to full on the dipstick, drove the car around the block it seemed to be slipping a little in third and it had a clunking or vibrating when acclerating and shifting (it did this with the other motor), I got under there saw a bad transmission mount and replaced that. checked the fluid and it was low so I filled it up. Now the car is slipping really bad in all three gears. 1. Did I over fill the transmission? 2. Could it be a bad converter? 3. I am going to change the filter and fluid, how much fluid should it take to refill? Quote Link to comment Share on other sites More sharing options...
Guest Posted August 28, 2006 Share Posted August 28, 2006 Smyth, double check the vacum line to your trans. check for cracks kinks etc. etc. Quote Link to comment Share on other sites More sharing options...
Guest Posted August 30, 2006 Share Posted August 30, 2006 What is your axle ratio? and how many high stall converters have you owned in the past? Quote Link to comment Share on other sites More sharing options...
Guest Posted August 30, 2006 Share Posted August 30, 2006 Axle ratio is 3.55. I have a drag racing cars for the past 5 years and wouldn't call a 2500 stall high, my 65 Dart with a 440 has .600 lift cam with 4800 stall in it now that I would call high. As for knowing how a stall converter works yes I do, there is significant difference between slipping and stall Quote Link to comment Share on other sites More sharing options...
Guest Posted August 30, 2006 Share Posted August 30, 2006 Smyth, double check the vacum line to your trans. check for cracks kinks etc. etc. Smyth, did you check these items??????? Quote Link to comment Share on other sites More sharing options...
Paul Bell Posted August 31, 2006 Share Posted August 31, 2006 This transmission problem started when you swapped to the higher stall converter? Did you do any other transmission mods? How's that hose and while you're at it, as well as the vacuum modulator? A bud of mine with a blown '66 got a converter tagged wrong. The tag was what he wanted but the unit was not. Quote Link to comment Share on other sites More sharing options...
wallaby Posted August 31, 2006 Share Posted August 31, 2006 As for the over-full question, your dipstick should be a good indicator . Too much fluid can be as bad/worse than low fluid. If the level is high enough it gets up into the moving parts of the trans and they whip the fluid into a froth. Once there is air in the fluid, it won't work for hydraulics...just like air in your brake lines. Your fluid should look clear and clean. If it looks pink or milky at all I'd replace it. Reading through your question it sounds as if it was working ok until you topped off the fluid level? Maybe one of the guys here can give you a measurement on the correct dipstick length just so you know yours is right. I know the TH350 also has a kickdown cable to the carb, maybe that is in the wrong position? Quote Link to comment Share on other sites More sharing options...
Guest Posted August 31, 2006 Share Posted August 31, 2006 Yeah the problem started when I swapped converters, I didn't pull the transmission, I was swapping motors so thats when I put the converter in. I did get a series of clunks when I took off hard or between shifts before I swaped the converter. I got the new motor in added fluid drove it around the block and the transmission did not slip, but did clunk or shake really bad. I climbed under saw a bad tranny mount and replaced it, I then checked the fluid running in gear and it was about 1 quart low, so I added the fluid. I tried to drive it around the block and all it would do is slip, in all 3 gears. I checked the vacuum line and that is fine, last night I changed the fluid and filter and there was some black gunk in there but no metal shavings or anything of concern. After a fresh fluid and filter change, I tried it and it is still slipping. I am not sure if the converter was not fully engaged (I did hear 2 clunks when I put it in) and it bolted up fine. At this point I am going to pull the tranny and swap it out for another I found, unless someone else has something else to try. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted August 31, 2006 Share Posted August 31, 2006 If you were able to move the converter after the engine was bolted up, it should have been seated correctly. Did you bolt the engine up first, or the converter? this may sound retarded, but are you 100% sure that it was trans fluid that went in there and not some other fluid that may have changed the clutches ability to grip? It's just strange that all of the sudden it is slipping. I'd normally attribute that to inadequate line pressure, or valving issues. I don't think your modulator would give you those problems, even if it was bad. I've run with no hose on mine before and it doesn't cause slippage, just not shifting in the right spots. Plus, when you floor it, your manifold vaccum is the lowest and you shouldn't get slippage then, so I think modulator is out. If the new trans is moving at all, the converter should be engaging the pump fine, otherwise it wouldn't do anyting at all. Did the clunking go away with the new mount? could it just be that it's worn out finally? Quote Link to comment Share on other sites More sharing options...
Guest Posted August 31, 2006 Share Posted August 31, 2006 Thanks for the reply. I put Dexron III right from the plastic container. I bolted the motor and trans then the converter. The converter spun freely with no problems prior to bolting the transmission and flexplate together. It seems odd to me to that it would just quit working. When I drained the fluid it was dark and had a fair amount of black sludge. I found another tranmission I am going to put in for now, then over the winter I plan on having a Th400 built for it. Quote Link to comment Share on other sites More sharing options...
Heckeng Posted August 31, 2006 Share Posted August 31, 2006 I agree, the whole thing sounds wierd! You'll have to keep us posted on what you find. As a side note, I normally use the B&M rebuild kits, and they always recommend Type F fluid. Be sure you check what fluid your rebuild kit prefers. The black sludge doesn't sound good. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted September 1, 2006 Share Posted September 1, 2006 btw.. if the vacum line to the modulator is off the trans will shift VERY late, or not at all.. and will shift VERY VERY hard. if the kickdown cable is too tight, you can't get to WOT.. if it's too lose, the trans will shift very early, but should not effect shift quality. (I drove my monte for almost a year w/o a kick down cable cuz I had the wrong carb and no way to connect the cable) just had to manually shift it if I wanted to boogie sounds to me like the front pump is going, or the converter is slipping way more then it should. I'd get a pressure gauge on that trans right away.. any book on servicing a TH350 will show you where to hook up.. but u need a hydraullic pressure gauge capable of 300-400psi. Quote Link to comment Share on other sites More sharing options...
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