quick tranny question
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Joined: Aug 2010
Posts: 7,322
Likes: 528
From: Ann Arbor, MI
A similar question came up in another forum that I tried to answer:
http://www.nastyz28.com/forum/showthread.php?t=271704
Since I wasn't sure if a spacer was needed or not, I contacted Chris from Circle-D and he gave me this detailed reply:
=====================================
Consider the distances in the area of the flexplate:
Standard Crank Offset from Crank - .315
LS Flexplate - .575
Spacer Height - .410
Flat Flexplate - .200
So the distance from the block to the flexplate is ~.900 either for the dished 4L60 flexplate or the 4L80 flat flexplate with the spacer. That will give you the proper distance for the starter ring gear and converter spacing. So what you need to watch out for is the converter bolt pattern and pilot engagement, The standard GM converter, including the 4L80/TH350/TH400/PG, pilot extends .~200 from the converter pad. The LS 4L60 or 6L80 converter has an extended pilot, about .500 from the pads. This allows it to reach the normal LS crank without any adapter or spacer. When you want to put a stock 4L80 converter on a LS block you have to use something to extend the pilot to reach the crank. The factory way is to use the spacer with the flat flexplate, good choice because it bolts in place. The aftermarket uses sleeve that installs on the converter pilot. You also need to make sure you have the right bolt pattern on the flexplate.
If you are using a custom built converter, it is typical to use a LS style billet front on the 4L80 so you can simply use the 4L60 flexplate setup. No extenders or spacers necessary.
One more element to add is the extended crank early LQ4. It essentially has the spacer built into the crank. So it will simply use the flat flexplate and a stander GM pilot setup. It can not use a LS style converter because it will bottom out in the crank before the converter pads hit the flexplate. - not good.
=====================================
In short, you probably will need a spacer with a stock converter, but no spacer if you order an LS-compatible converter from e.g. Circle-D.
http://www.nastyz28.com/forum/showthread.php?t=271704
Since I wasn't sure if a spacer was needed or not, I contacted Chris from Circle-D and he gave me this detailed reply:
=====================================
Consider the distances in the area of the flexplate:
Standard Crank Offset from Crank - .315
LS Flexplate - .575
Spacer Height - .410
Flat Flexplate - .200
So the distance from the block to the flexplate is ~.900 either for the dished 4L60 flexplate or the 4L80 flat flexplate with the spacer. That will give you the proper distance for the starter ring gear and converter spacing. So what you need to watch out for is the converter bolt pattern and pilot engagement, The standard GM converter, including the 4L80/TH350/TH400/PG, pilot extends .~200 from the converter pad. The LS 4L60 or 6L80 converter has an extended pilot, about .500 from the pads. This allows it to reach the normal LS crank without any adapter or spacer. When you want to put a stock 4L80 converter on a LS block you have to use something to extend the pilot to reach the crank. The factory way is to use the spacer with the flat flexplate, good choice because it bolts in place. The aftermarket uses sleeve that installs on the converter pilot. You also need to make sure you have the right bolt pattern on the flexplate.
If you are using a custom built converter, it is typical to use a LS style billet front on the 4L80 so you can simply use the 4L60 flexplate setup. No extenders or spacers necessary.
One more element to add is the extended crank early LQ4. It essentially has the spacer built into the crank. So it will simply use the flat flexplate and a stander GM pilot setup. It can not use a LS style converter because it will bottom out in the crank before the converter pads hit the flexplate. - not good.
=====================================
In short, you probably will need a spacer with a stock converter, but no spacer if you order an LS-compatible converter from e.g. Circle-D.