With great difficulty- by myself today I hossed my turbo 350 into my 65 with 455. I bought the Coan max performance converter everyone says is bulletproof..... After getting it all close I got 4 bolts in and tightened them 95% of the way in between block and tranny housing. When I went back under the car I then discovered the bolt holes were not aligned between the flex plate and converter - so I tried to spin the converter to align it and it wont budge-AT ALL! I tried everything - it wont spin...it also wont move forward or backward at all .......The snout of the converter is in the end of the crankshaft and I have 1/8 to 1/16th betwen the converter mount pads and the flex plate. Any suggestions ? After 8 1/2 hrs on my back I am tremendously frustrated and out of ideas..... Someone mentioned the T350 shaft needed to be ground down on their T350 tranny when using the Coan max performance converter ? Anyone else have this problem with T350 and the Coan Max performance ? Any suggestions please ? UPDATE: 7-8-07 One helpfull member on here claims he had to grind down the "tapered" part of his turbo 350 pumpshaft in order to get the Coan Max performance converter to fit. He said not all turbo 350's have a tapered shaft ? Is this true ? I have emailed Coan to see what they have to say about this. Thanks J.
The converter is not all the way in and seated. Sorry to tell you this, but the trans will have to come out. When you get it out. pull the converter off. Pour a quart of trans fluid into the converter. Line up the 2 pump slots on the converter hub with the tabs in the transmission. Then push the converter on. Spin the converter and push, spin and push. There are several sets of splines that have to engage. You will know when everything lines up, there will be over 1" between the converter bolt pads and the bell housing mounting surface. Your converter is not fully seated and it is binding. That is why you can't turn it.
Thanks Larry one member claims turbo 350's have two pump shaft types one has a tapered shaft and one a flat shaft...he claims Coan told him to grind the taper off the pump shaft . He did and it fit then.....I will try what you say and I have also shot an email to Coan. Have you ever done a Turbo 350 to Coan MAx performance install yourself ? Thanks for all yor help. J.
I wouldn't grind anything until you talk to Coan. I can tell you this, the tolerances in a quality converter are tight, and sometimes it takes some time and effort to get the converter seated. Just be patient. Like I said, getting the pump slots lined up first makes it easier.
J, pull the tranny back out. Check that you do have the converter seated all the way in first like Larry said. I thought this was my problem at first too, but I did have mine seated all the way. In order to grind the shaft properly you'll need the tranny out anyway. When checking to see if your converter is seated all the way, take a straight edge across your bellhousing, then measure in to the mounting pad on the converter, you should have 1-1/16".
Larry heres a pic showing the converter registration and how close it is to the flex plate-crank bolts...do you still think its not on properly ? J
Thanks Jim ..I will get under there later today and take that measurement- thanks for you and Larrys help ! J.
Larry, this is exactly what I had to do with mine. Believe me, I wasn't impressed having to grind the snout of the input shaft. But Art assured me this does happin from time to time. Mine's been in for over 2 years now and everythings been good. The 1/8 to 3/16" taper on the end of the th350 snout is what I needed for proper clearance.
Jim, so you just grind down the taper portion only ? Approximately how much material is that ? What tool / grit did you use ? Depending on what Art says Monday and or I find today I may be headed the grinding route. I cant see it now but I am 99% sure mine is tapered as yours was . Larry I just went out and crawled under...... the converter on the tranny side isnt bottomed out against orange pump seal ? Its really close though -should it be ? My gut tells me its all seated right.....I have things to do today so maybe this afternoon I can take another crack at it all - no matter what it looks like I have to take it all out again - what an absolute pain in the xxx. Thanks for the help.
Jim, so you just grind down the taper portion only ? Approximately how much material is that ? What tool / grit did you use ? Depending on what Art says Monday and or I find today I may be headed the grinding route. I cant see it now but I am 99% sure mine is tapered as yours was . J, I'd first check the converter to make sure it is seated, then go from there. You need to take approx 1/8 to 3/16 off the end. In your pic are the flex plate bolts making contact with the converter?? I so, that's no good. I didn't have any issue with that. All I needed was the little bit of clearance for the mounting pads. Did you get my PM.
No they are not touching....my gut is telling me it is seated properly- I was pretty aware of that ...its got to come out for sure to get to the bottom of this all. Here are the converter pads to bellhousing face measurements you spoke of earlier for posterity-sake-others to refer to .....I will update tomorrow ...I just cant believe I have to pull this thing again ...If I would have known this potential grinding bit I wouldnt have bought that particular Coan. Just checked - did get your pm .....Thanks for the help .... GM Turbo-Hydramatic 350 1 1/8" from Bell Housing to Pads GM Turbo-Hydramatic 400 / 4L80E / 700R4 1 3/16" from Bell Housing to Pads GM Powerglide 1 1/8" from Bell Housing to Pads *Distance may vary either way .050".
If it is seated in the pump, and not touching the flexplate yet, but won't easily spin, it may be in a bind where the converter indexes to the crank. You should NOT have to grind the input shaft on the transmission to make a converter fit. Send it back to Coan and tell them to exchange it or refund. You took a converter off that input shaft and it fit, so a new converter with proper clearances should fit it. In other words you have a known good shaft and converter and the only item changed is the converter, if it doesn't fit, it isn't the input shaft. Aftermarket converters do sometimes fit tighter, but this is usually due to the hub and pump bushing fit, particularly on a fresh rebuilt trans. Coan makes a good product but don't start grinding on known good parts to fit their converter. If you are grinding a taper, you are just making it easier to force it into the converter stator, that a BS way to make it work. Some aftermarket converters have an adjustable snout. It is threaded and you can screw the snout further out to index deeper into the crank. Be sure it doesn't have this and it is screwed out too far.
Ok all I got under again tonight and moved the tranny ,,,I measured and voila I did have the required 1 inch measurement from bellhousing face to COAN converter mounting pad people here and Coan told me to measure. This supposedly indicates the converter is seated properly. I also scraped the paint off the snout of the converter and made sure nothing was in the end of my crank. I mated it all back up together and ended up with a 1/16th space between the flex plate and converter wings / pads.....this time however the converter will rotate but you cant spin it freely or move it back and forth. Is this correct ? If I bolt it up I dont know if it will pull the converter snug 1/8th up to the flex plate or not. Is it ok to run 3 1/8th thick washers on each converter pad and just snug it all up or is something still wrong here ? H E L P .....J
The converter must have some play between the flexplate and mounting pads, and you need to pull it out 1/8" or so to the flexplate so that it isn't applying pressure to the pump gears, or they will live a short life. It sounds as if your converter snout is very snug in the crankshaft pilot area. Take some sandpaper and sand the paint off the converter in this area, be sure the crank doesn't have a burr or other obstruction, remove any pilot bushings if they are in the way, and use some light oil on the inside of the crank so it will slide easier.
I scraped off the paint on the snout last night before reinserting..I also put a light coat of oil on both the snout and pilot recess. Someone suggested putting a light pry bar in there and seeing if it will move forward the 1/16th -1/8 th towards the flex plate ...sound like a good idea ? Are you saying the crank may have some sort of removeable bushing inside of it ? How free should that converter spin ? Right now I grab it ,rotate it with one hand and it stops maybe going another inch or so in rotation after I let my hand off of it. Thanks J.
I would go ahead and start all three bolts finger tight, and then wrench them about 1-2 threads at a time each, rotating the motor/flexplate/converter 120 degrees each time to do all three bolts evenly. (I know it's a paint to keep getting out and turn the motor--unless you have a flywheel wrench, which makes it much easier.) I bet it will smoothly snug up and push the nose into the crank. Just watch to see that the flax plate is not flexing, and stop if the bolts get hard to turn before it snugs up.
A friend of mine who has built around 20 cars tells me he doesnt advise me using this converter as it wont move forward or backward. He says he toasted a crank thrust bearing in a 454 Chevy this same way. After teardown on the 454 and discovering the problem he had to have the snout of the converter machined down. He says you need the crank and converter to be able to float a few thousandths back and forth or this very thing will happen. Any input or ideas here would be great . I have a question : When you are tightening the 1/8 th gap up between the converter whos nose is buried in the crank and the flex plate what moves ? Is the converter being pulled further into the crank recess as you tighten or is the flex plate flexing towards the converter and filling the gap that way ? Im thinking of sending this converter back to Coan as this shouldnt be this hard. It should just be a bolt on. Ps the converters snout measured 1/2" long last night.
