Calling all -Turbo 350/455/Coan Max performance converter installs

Guys as you may have seen from my other thread I had the day from hell under my 65 yesterday- 8hrs trying to get my turbo 350 and Coan max performance converter installed behind my 455. I was wondering if anybody else has done this exact install (TURBO350-Coan MAx performance converter) and if it installed with no problems encountered or you had problems also. J.


FYI -One knowledgeable member tells me I may have to grind my tapered turbo 350 pump shaft down in order to make it fit as Coan told him to grind his down. Another very knowledgeable member has told me I simply dont have it seated properly on the shaft and thats why it wont move forward or backward and why it wont rotate....I need to reseat the converter..J. .

 

a coan convertor is really tight on the splines of the shafts it just needs
some finesse to seat it othewise you will damage trans pump
take your time
maybe wire wheel the shaft but dont grind on it
i would do either but i have installed many transmissins and so i
can kind of guess if its not bottomed

 

I will be doing this exact same deal hopefully later in the week.

 

WOW! I put one of these in last year and thought I'd lost my touch with converters. The first "clunk" was easy as usual but getting it to the second "clunk" (seated position) was a bear. I bet I had to do the lift, spin, push thing about 40 times to get it to seat. Comparing the hubs from my old Dynamic against the Coan and wow what a difference. The Coan had some very square edges and the surface finish was nicer. Those square edges for the pump slots may be a bit tight for you pump though. I agree I'd hate to file/grind on it but I doubt it will hurt anything as long as you keep the dust out of the converter guts. You shouldn't need to do much just a few thousandths and I bet you'll be golden.

let us know how it goes.

 

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

 

dont use washers , try a pry bar to bring it forward but the not spining thing makes me wonder something is not right .
keep trying to get it to spin

 

Andy ....It will rotate but it doesnt like freewheel spin..should I be able to grab it spin it and it spin freely ? J

 

it will be a little tight but it shouldnt take much to get it to move
spin it a full turn and see if it has a tight spot or any odd feeling or noises
if you can get a full spin out of it and all seems good go ahead an bolt it down ,fill it up and start
that will tell anything else you need to know
did you fill convertorbefore install,if not just let it idle to fill convertor
try gears see if all is good

 

My transmission rebuilder friend mentioned something that he liked about using Coan converters. Most companies cut a converter open on a lathe, rebuild the guts then weld it back together. You just lost about an 1/8 inch of converter due to the kerf of the lathe cut. If you get a converter thats been built a couple of times the tolerances go out the door and you might end up having to us washers between the flexplate and the mounting tabs. This is exactly what happend with a cheap converter I used about 10 years ago. According to him Coan actually maintains the correct hight (not sure how) when they build a converter. You need to have a bit of front to back motion in the converter to allow for expansion and a bit of swelling in the converter under heavy loads, otherwise you're thrust bearing for the crank will feel the pain. If all you have is an 1/8 of an inch front to rear play and it moves by hand I'd bolt it together and see what happens. Depening on which flexplate you are using you may hit a counter weight.

Re-read your post mid-reply and it seems to me..

1. It would not rotate
2. You pulled it out, cleaned the paint off the snout of the converter
3. Now it rotates but take a bit of effort.

That just sound like you may have a crank with a small side of tolerance hole and a converter with a large end of the tolerance size hub and you are getting just a bit of drag.

Given what you've said I still think I (personaly) would bolt it together and see how it runs.

regards

 

Thanks to all for the help / advice ....I believe it is resolved now...

" I Pulled the tranny again , measured the crank hole and the convereter snout ...I took multipe measurements....the snout- without paint -diameter measured 1.706 my crank hole measured 1.700 ! Add a little paint thickness variance to that and its worse. So aware of this measured mismatch I then took the converter to my bench and wire wheeled all the remaining paint off the converter snout where you could see it was stopping....I also wire wheeled it for quite awhile to "possibly" take material off the snout. Even though there wasnt a thing in the end of my crank I went ahead and scotch brighted it anyway and greased it liberally. My Turbo 350 shaft did have a taper on the end of it about 1/8th long. Coan said GM ran with this shaft for ~2-3 years. Resolving myself to not taking this tranny out again I took Gusszgs advice and ground down my 1/8th taper on the very end of the trans pump shaft. Hes been running for 2 years with no problems after doing this mod- so thats good enough for me. I put it all back together and bolted it up. I can now move the converter 1/8th back and forth and it rotates. Looking back I think it was a combo of the paint on the snout, "possible" slight oversize on the converter snout (from what I measured) and that extra 1/8th tapered pump shaft length. Its in..thanks for everyones help and lets see if it lasts down the road. J

Side bar - I just so happened to have a brand new "Pro Torque ss model" converter laying around and their snout measured considerably smaller diameter at like ~1.6 something. I have that measurement at home - might update later with that exact number - also fitted it to my crank (much easier than Coan went right in) BUT the extremely wide mounting ears on that converter hit my balancer weights that are close to the mounting holes so it was unlevel and unuseable in my eyes in my application. The Coans nice small pads/ ears fit no problem.

 

Just put a Coan Max Performance 10" tonite. 1.5 hours, no issues at all o No: . It went click, clack, clunk, with the clunk being the one that pinched my fingers :rant: . My 350 input shaft is tapered, too. Took it out for a quick test, and the engine gets right into the power band. :eek2:

 

How is that Coan on the light throttle, or highway slipping alot on light load?

 

Bob, which converter did you order? They make a 258 and a 265mm of the "Max perf" ones. Was it one of these?

 

Before I give a "review" of the converter, I want to drive the car some more.

 

I guess I don't know. o No: It's round and black.

It may be a COA-20320, but it was definitely $665. I can check my paperwork when I get home. I ordered it through AM&P.

 

:laugh: OK then........how about a part # then.

 

Here are pricing and p/ns for the Coans from their website ....

"COA-20320 10" MAXIMUM PERFORMANCE CONVERTER $665.00
COA-20320-2 10" (258mm) MAXIMUM PERFORMANCE CONVERTER $877.50"

J.

 

There's also another one COA-20320-3 265mm for $877.50. Not sure the difference.

http://www.coanracing.com/Catalog.asp?CatClass=02CO

Scroll down to Max Performance.

 

Bob, the reason I asked about the converter is I'm wondering about this 258 and 265mm difference. Why the two different sizes, and what for?? Also over a $200 increase in coin. Could this be allowance for the different input shafts as previously discussed? Just curious.....as they never offered this when I bought mine 3 yrs ago. I got the 258 mm, and had the grinder out.
Kinda funny...7mm is approx. 3/16" and that's about how much I had to grind off.

 

Jim, the part number on my converter from AM&P is 20320-B. I don't see that one on Coan's website. I don't think it is a 258mm one, because when Mike P. was describing the choices, he said some thing to the effect "and then there's the 258 mm that's hot right now" and went on to explain that the reason for $200+ more is because the internals were beefier. My choices were $434, 665 and 877, and he explained the differences to me that I have since forgotten most of.

Like I said, he was VERY adamant about no grinding. Although you would hope someone offering help on the phone of a very reputable co. (Coan) would know what they are talking about, I sometimes cringe when I hear my wife try to help me at my shop by offering advice that makes no sense whatsoever.

On the other hand, Jim, how long has your combo been together with no ill effects? It's been a while probably, but do you remember a click, clack, and clunk? Sometimes you have to pull the converter off the "landing" of one of the steps just a bit in order to be able to push it on to the next one. I also always look at the clearance between the back side of the converter and the transmission. When the converter is seated correctly, there is very little room, and you will pinch your fingers. I have replaced over 100 auto transmissions and don't ever recall having the problems described above.