converter clearance

[det0326 179]

Need some help from some of you guys that has done the AOD conversion. I have a 1991 351w and AOD tranny from a Bronco. When I put the converter in the tranny I had read that if you put a straight edge across the face of the bell and it cleared the hub that goes in the rear bore of the crank it is in as for as it will go. So that is what I did and when I coupled the engine and tranny together the studs in the converter had to be lined up with the holes in the flex plate which I didn't think to much about it at the time but now I wonder if that was normal. Should the converter go farther back so that it can spin to line up after the engine and tranny is put together. I know the FMX converter had bolts instead of studs so I am not sure how the studs are suppose to work. Anyway fast forward to where I am now it's all in the car and ready to start actually and I decided to check the thrust clearance  on the crank ( I know should have done this long ago ) sometimes I just forget. I did not build the bottom end but was built by a local engine builder that actually builds engines for the local racers so I assume he should know what he is doing. Anyway I wish I had checked it at that point but I didn't  so now my dilemma after trying to check it in the car I cannot get the crank to move forward or backward. I had read that if the converter is not seated then that can cause this problem so i loosened the converter bolts and tried to move the converter back but will not move any but it will rotate a little back and forth because of a little clearance in the holes which is normal but this tells me that the converter hub is not binding in the crank.  So the big question is do you guys think the converter is where it needs to be are should it slide back for enough for the studs to clear the flex plate? Thanks for any and all help. BTW everything is stock. The crank is OEM but is not original to the engine it is a regrind.

 

Dave

[prayers1 153]

Dave,
I've attached installation instructions below that might be of some help. This is what was pasted onto me from the guy who rebuilt mine.

IIRC, I had a hard time installing the TC to the flexplate, I had to round out the holes in the flexplate for the TC to fit, but once it was installed I couldn't move it back as one would expect. When I pulled my motor and tranny out last week I loosen the TC nuts and tried to push the TC back to get it off the flexplate, still it wouldn't bunge but would rock side to side in the flexplate bolt holes. I eventually had to loosen the tranny bolts and pry a little to get it to loosen up then it slid off. During the time the motor and tranny where running I didn't experience any problems.

 

The important part the tranny guy stressed was to make sure I heard the 3 clunks of the TC siding onto the input shaft of the trans.  I had to do it a couple of times because I didn't hear 3 clunks, but found I was right even w/o hearing the clunks.

 

I know your past this point but I hope you can find some info in the instruction sheet to help with whatever.

 

TRANSMISSION RR GUIDE rev2.doc

[RPM 1,190]

Just fyi, all 3 of my FMX TC's had studs.

[det0326 179]

Thanks John for the info.  From what your saying it sounds like what I have so that makes me feel confident that the converter is where it needs to be. If the converter had not made the last clunk into the pump I don't think it would have went together as easily as it did. I actually pushed it together by hand after lining the studs up with the holes in the flex plate. 

 

Bob thanks for the info also, the one FMX I had with converter had bolts, could have been an aftermarket converter I don't know.

 

Thanks again guys

 

Dave

[prayers1 153]

Curious, what gears in the rear and stall do you have?

[det0326 179]

Curious, what gears in the rear and stall do you have?

 

John I have a modified 8.8 from an explorer, the gears are 3.73: 1 and the converter is a 2600 stall

 

Dave

[MikeStang 247]

Do yourself a favor and Don't start the motor yet.

The 351W Stock cranks were not ever cut deep enough in the pilot area to accommodate what is known as a long Snout converter until after a certain year if I recall from my readings.

I burnt out a thrust bearing and my trans went together with the block pretty much as your describing.

Will post more in a bit have a meeting.

Don't fire it up yet

[MikeStang 247]

Measure the pilot hole depth in the crank, then go measure the Pilot Hub length on the converter.

If the hole in crank is not at least .010-.015 deeper than the length of the converter pilot hub I wouldn't run that converter personally.

The stock converters for AOD/AODE/4R70W usually all have short studs on them instead of bolt holes.

 

When you think you have the converter seated all the way in the transmission you should not be able to stick your hand into the area between the converter and bell housing at the top, that is ONE Indication you got it all the way in.

Now take a straight edge and lay across the bell housing and measure from the mounting pads on the converter to the bottom of straight edge...for an AOD it should be 1" or a little more. AODE 1.030" but distances can vary up to .050 plus or minus and you are good.

If you do indeed have it seated, go ahead and install trans and converter on to the motor being sure the trans is seated all the way before tightening up the bolts, don't use the bolts to pull the trans up.

If your converter has studs be sure they are lined up with the holes in the flex plate because they may or may not go into the holes.

Now once its bolted up be sure the converter is seated into the trans still by rotating and pushing it backwards as long as the studs didn't go into the bolt holes. If they did go in slightly that is okay.

Now get a set of feeler gauges and measure the distance between the flex-plate and the mounting pads on converter.

If the Gap is between .060-.185 your good to slide converter forward and bolt the converter up.

If however the converter mounting pads are already in contact with the flex plate, your converter is either slid out and not seated OR you will need another converter....

You should always have some converter pull out...

The converter exerts a forward pushing FORCE on the rear of the crank, and I am not talking about converter ballooning either, its got something to do with hydraulic pressure created by the trans and transferred into the converter that pushes it out, and that is where the flex plate is supposed to absorb some of it and FLEX, hence the name Flex plate.

Now if you have no pull out on the converter you have eliminated the air gap and effectively removed a large margin of the flex plates Flex thus pushing it past what it is designed to handle and THAT is when it gets transferred into pushing on the thrust bearing to excessive amounts.

 

So you see it could be Several factors that can cause Thrust failure.

1. converter not seated.

2. Converter Pilot hub bottoming out in crank pilot

3. No pull out on the converter.

 

Essentially if the hole in crank isn't deep enough and you bolt it up its already a no win situation.

The hole should be deeper and there should be converter pull out because as the flex plate flexes forward, the converter pilot hub moves forward, and if it bottoms out in the pilot hole before the flex plate can do its job, you just killed a thrust bearing.... Now Ask me how I know all this wonderful information LOL

[Cruzzar 22]

I helped a friend put an AOD behind a 351W and with the converter seated into the trans it still made contact with the flexplate. After a long discussion with the trans shop that supplied the flexplate and the rebuilt trans they said to bring the flexplate back and exchange it for another that had less offset than the one we had been given. Evidently they made more than one flexplate with different offsets. After replacing with the new one we has a small clearance between the torque converter mounting studs and the flexplate after bolting up the trans to the engine. Probably not what you wanted to hear. This may not be your problem but something to consider.

[MikeStang 247]

Yep there are a few different offsets for the flex plates as well.

[det0326 179]

well Mikestang unfortunately after John said he had the same setup and described his as being similar I started the engine up I ran it long enough to bring up to operating temp. I did this a few days before you posted the first time. So good are bad it has been run and don't know if it hurt anything or not.After more research on the issue it may be the flex plate at fault .  Here's the set up that I have it is a 351w from a 1991 bronco that I thought original had an AOD but turned out that the person I got it from said it had a E40D .  So what I have in the car now is the original E40D flex plate with a 1991 AOD behind it. My question at this point is there a different between an AOD and E40D flex plate? Personally I do not know and can't seem to find any information to confirm either way. Any body know the answer to this question I would be much appreciative.

 

BTW everything sounded good the converter is in the pump and working because the fluid level went down and had to top off. The tranny does go in gear forward and reverse.  I sure hope i didn't hurt anything. 

 

Dave 

[MikeStang 247]

My car ran perfectly fine for several thousand miles, and even when I found I had a thrust problem the motor ran fine, it just felt down on power a little bit.

I know NOTHING about an E40D transmission.

long as you had some pull out room on the converter you should be okay.

[det0326 179]

I helped a friend put an AOD behind a 351W and with the converter seated into the trans it still made contact with the flexplate. After a long discussion with the trans shop that supplied the flexplate and the rebuilt trans they said to bring the flexplate back and exchange it for another that had less offset than the one we had been given. Evidently they made more than one flexplate with different offsets. After replacing with the new one we has a small clearance between the torque converter mounting studs and the flexplate after bolting up the trans to the engine. Probably not what you wanted to hear. This may not be your problem but something to consider.

Thanks Cruzzar  for the info I think you maybe right about the flex plate.  The one you and your friend worked on did it contact the flex plate enough to prevent it from going together?  Mine actually slide together by hand but there is no back and forth movement at all that I can tell, however it will rotate on its axis as far as the clearance will allow in the stud holes.

 

Thanks again

 

Dave

[det0326 179]

best i can tell offset on flex plate that on the car is about .100 difference than the AOD flex plate that came with the tranny but it is for a 302 with 50 oz imbalance .  What car do I need to look for the correct flex plate for 351w 28 oz imbalance, I know some 302's or the 5.0 one had 28 oz didn't they.

 

Dave

[Cruzzar 22]

As I recall the trans would make contact with the engine block without forcing it but there was no clearance between the flex plate and the converter. I don't remember if the studs could be rotated in their respective holes when the trans was buttoned up to the engine. Would this small amount have caused problems I can't say but after changing the flexplate we has a small amount of clearance to pull the converter up against the flexplate after the trans was attached to the block.  I suspect that if you take the flexplate to a good transmission shop that they would be able to identify it and locate another with more offset.

[MikeStang 247]

If I recall the FRA-205 Flex plate from Auto Zone should work... its 28oz imbalance with 164 Teeth.

[MikeStang 247]

88 Crown Vic with 351/AOD is what you can have them look up

[MikeStang 247]

Ford part number of E0AZ-6375-A for a late 80's to early 90's Crown Vic w/5.8 and AOD.

[det0326 179]

thanks Mike 

 

Yes I found some info on them over the week end and have it on order. Another one that will work too is a 164 tooth C4 up to 1980. 

The tranny is on the floor and it appears that the flex plate that was on the car has a .100 longer offset and that was my problem.

Thanks again Mike and Cruzzar for all the good info. I'll dance at you guys next wedding just let me know. LOL

 

Dave

[det0326 179]

Got flexplate today and installed it got the proper clearance now. I used a Hays 12-030 very nice piece great quality and USA made.

Thanks all

 

Dave