School me on trans basics

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JoeSBP

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gents, looking for some help with my 904.

I'm running a 3500 stall converter and manual 904 from hughes.
Now that it's nice and toasty in NC, I started to notice a slight vibration right at 2950-3100 rpm. I can ease right in/out of it while cruising under very light throttle.
I have been tinkering with the cruise timing (vacuum advance) on the Fitech, and at first thought I was throwing too much timing at it. Then she started leaking intermittenly, but only when it was pretty hot outside, and I had cruised on the highway 20+min. I've got 3.23 out back and that puts me right under 3k rpm when cruising. Ran her a few nights ago, and on the way home, the torque converter bolts started intermittenly contacting the dust cover. PO also installed a pair of tube/fin style coolers under the car, impressive. Fluid is still clear and doesn't smell burned, level was spot on, but it did have some aeration on the stick..

So I think what I have is a very warm and angry converter/trans.
Plan is to:
1. Install a TruCool M7B in front of the radiator
2. Install a cast deep sump pan with x2 bungs for drain and temp sender(any suggestions?)
3. re-gear to 4.10

any other suggestions on things I should be looking at?
 
I think you found your problem, but are looking elsewhere. Remove the converter cover, and check that bolts are tight, then i would get under there while it's running, and see if the converter is running true.
 
all bolts are tight and uniformly scuffed. with the inspection cover off at idle, no percieved wobble or vibrations. My first thought was I had a bolt backing out, but i'm thinking it just swelled a little..
 
so I have read that cruising below stall will build up excessive heat, but I have also read that under light throttle, its not really slipping that much. 4.10's will put me right at stall, but i sure would like to spin it slower if I can..
 
I run a 904 with a converter that stalls right at 4000 and 3:23 gears with 28" tires so even at 70 mph it's only spinning 3k. According to my temp gauge it doesn't get over 150 when cruising on an 85* day. Almost every weekend we hit a cruise and we live in the middle of nowhere so nearly all cruises are 40 miles away. A loose race converter might slip enough to generate too much heat but a decent street/strip converter made nowadays usually doesn't. Hughes converters from my experience are decent converters and don't usually slip much under light throttle
 
What is the suggested inner diameter for cooler lines? Plan on using push locks fittings and flexible hose.
 
I've wanted to install a temperature gauge on my transmission cooler lines and I think this would help you tell the story here. I do have my heat gun and try and take inventory from time to time with that and everything is been good I haven't seen anything over 135 yet but I sure would like to really know.
 
after reading around, I think I'm going to put my sender in the oil pin. Reason is not all the fluid makes its way through the cooler. Some empties directly back into the pan. So you could have different temps in the to cooler line, from cooler line, and in the pan. I'm thinking I'll go off the temp of fluid in the pan the trans will be drawing in..now I have zero actual experience with this, so I'm open to any and all suggestions..
 
Not sure it really matters. The oil is constantly getting "mixed" on return from the pan
 
thats why I want to pull from the pan. "hot" fluid is going to either drain back to pan, or be routed to the cooler, "cooled" fluid will be routed back to pan, so taking your measurment at the pan is the average temp. Now I can see value in pulling from the out going line to the cooler. Allow you to see temp spikes etc. I can also see value in pulling from the return line from the cooler. Allow you to see just how efficient your cooler is performing. But since I'm only going with one gauge and one sender, I think in the pan will give me a good view on the over all function.
 
What is the suggested inner diameter for cooler lines? Plan on using push locks fittings and flexible hose.
The factory lines were 5/16" tube which has an I.D. of about 1/4" but the adapter fittings that screw into the trans are 1/8" pipe so unless you change them also there's really no need to go larger than 1/4" i.d.
 
Any trans gurus know why the factory adapters are only 1/8"?

Maybe to intentionally reduce flow to cooler and put more back in the pan until fluid is warmer?

I don't want to mod on assumptions and causes headaches later.
 
Any trans gurus know why the factory adapters are only 1/8"?

Maybe to intentionally reduce flow to cooler and put more back in the pan until fluid is warmer?

I don't want to mod on assumptions and causes headaches later.

Because under normal conditions that is all they needed to be.
Those 1/8 fittings can be drilled out some for more flow if you would like, but it won't make much difference.
Also don't forget that they are 1/8 at the radiator as well.
You will also not adversely affect anything to increase the cooler system flow as far as the trans function goes.
 
Between a external cooler and a deep pan, you should be fine.
I'm not sold on the "swell" aspect of it all.
 
ran it today just to recreate/validate the issue. When its cold, no contact/no vibration. after 25-30min steady cruising 2500-3500rpm( I'm on all open range roads to work) I start to feel a light vibration right at 3000rpm. Once rpm get down back to idle with no load, I get converter bolt contact to the dust cover uniformly on all bolts
 
not sure, I'll have to go through reciepts and take a look once I get home and get it up on some jack stands
 
I didn't see any cracks on it with just the inspection cover removed. can it be cracked/shifted at the crank?
 
I'll get it up in the air this evening and have some touchy feely time with it
 
I didn't see any cracks on it with just the inspection cover removed. can it be cracked/shifted at the crank?

They can crack right around or even directly from one to the next bolt hole at the crank as well as from the center out, like you might see with the cover off.
The big problem is if it gets bad enough to take out the trans pump before it gets caught, and an off balance problem like you described with heat changes and (sometimes) contacting the block could very well indicate that this is exactly what is happening.

flexplate_out_2.jpg


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ran it today just to recreate/validate the issue. When its cold, no contact/no vibration. after 25-30min steady cruising 2500-3500rpm( I'm on all open range roads to work) I start to feel a light vibration right at 3000rpm. Once rpm get down back to idle with no load, I get converter bolt contact to the dust cover uniformly on all bolts
Do you have the correct flexplate bolts in it? They should have a real thin head. A standard bolt head is much thicker and will make contact with the flexplate access cover
 
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