One of the most common questions we get is about converter spacing/clearance, not well understood and can be confusing. I wanted to try and explain why we want 1/8” spacing and hope that will help you guys understand it better when you are installing a converter.

When installing any converter, measuring and setting the proper converter clearance is critical for proper operation of the converter and transmission. It can get a little confusing and reading on the internet all you see is you want an 1/8” clearance. What does this mean and why does it matter? The goal is to have 1/8” space between the converter hub and the transmission stator support once you pull the converter forward and bolt it up. You do not want to bottom the converter out or even worse, have negative clearance forcing it into the stator support or pump gears on start up, that will damage your converter and transmission. The converter does move in and out of the transmission, which is why the 1/8” is there to ensure the converter can move some and not bottom out in the transmission. But you do not want to have too much spacing where the converter might pull out of the pump gears and cause a major failure. I am sure you have read a thread about a 4L60 pump rotor breaking costing lots of money. Probably happened because spacing was over the 1/8” and the converter pulled out of the rotor. This is why you might need shims if the spacing is over an 1/8”, to move the converter a little closer to the trans for proper pump gear engagement. Another interesting factoid - That is why the flexplate is called a flexplate, it will flex absorbing the thrust from the converter moving in and out of the transmission.

Chris

 

Adding to that, I suggest keeping on eye on the converter to flexplate spacing (gap) as you bolt the trans bellhousing to the engine. I suggest not going more than finger tight on the bolts before you confirm that the converter spacing is good.

If the bellhousing is flush with the engine block and you have a gap between the converter and flexplate, you can be sure the converter is fully seated. If instead you find that the converter is tight against the flexplate, this indicates that the converter is not fully seated and you will need to remove the trans and try again.

The easiest way to test the gap is with drill bits. The largest one you can slide between the converter mount pad and the flexplate is the gap.

Other experts say that a gap of between 1/16" and 3/16" is fine, with 1/8" being optimal.

 

Good suggestions mrvedit. Also a good idea to measure the converter pad to bellhousing before installing the unit in the vehicle. You should see just over an inch. You can measure the OE converter before you remove it for a baseline number.

Chris

 

I'm thinking that this should be a very consistent gap. what can cause the gap to be too big? how often does this happen?

 

Flexplates vary some...as do converters. I have seen OE flexplates vary by .050. Converters obviously vary by different manufactures. Take the 4L60 LS for example. OE converter is typically around 6.500-6.550, but we have seem them as short as 6.450 from some manufacturers. Take that with a shorter flexplate and you have a major clearance problem. Our target height is 6.525-6.575, that seems to eliminate shims for the most part. But we always suggest to check it.

Chris

 

Thanks for the info guys, just about to put my motor and trans back in
so this post is very helpful and timely.

 

Many a thread containing a tale of woe has been posted here due to failing on this. So much so that I was freaky about it during my two converter installs. But I was working with experienced techs at my buddy's shop.

Another confidence builder is getting the three "clicks" as the converter mounts on the input shaft. But nothing substitutes for the right measurement.

 

Here are some pics to better describe the "Why" on converter spacing with some close up pics of converter hub installed in a pump rotor. - 4L60 LS setup. First is a converter hub seated all the way, zero clearance. Second is with the correct .125" spacing. Gives it room to move in and out of the trans some, but with good engagement. Third is with .200 spacing, looks like it can come out with some movement - not good. Hope this gives you a better idea of how important this is.

Chris

 

Good thread.

 

Pics are really helpful, thanks Chris!

 

Them pix put it all in perspective! Seeing is believing!

 

Good timing with finding this thread since I'm installing my Yank SS4600 in the 4L60!

 

On my way, right or wrong?

http://finnshark.com/forum/showthrea...=11565&page=41
# 405

 

Are those calipers in CM? Looks like about 38mm?

Chris

 

I think you meant 3.8 mm = 0.15" which is within the .065 (1/16") to .195 (3/16") range.
So yes, looks great, no need for washers.

 

Missed the dot...sorry about that. And yes assuming that is correct, then the spacing is fine.

Chris

 

Thank you guys! Car is ready for driving. Now we are only waiting the summer and driving season. I hope that pics will help others too.

 

This is an older thread but I'm redoing my transmission right now and I'd like to know how to set the spacing on a C5 Corvette. Things are a little different on the Vette.

 

Same concept and clearance targets. Only real difference is you will be working in the back of the car.

-Brian

 

Thanks Brian. I have the Corvette Service Manual by Chevrolet and it refers to the flexplate in front of the torque converter and the flywheel behind the engine which is confusing. Does the C5 have two flexplates or is the flywheel referred to in the manual actually a flywheel and not another flexplate. (Automatic Transmission - 4L60E/4L65E Pages 732 - 735) I ask because I was considering replacing the flexplate while redoing the trans and I'm not sure which part or maybe both should be replaced. A little clarity on this point would be appreciated.