LS swapped c20, replace th350 with 4l60e

[cjdock]

Little bit of an odd question...
So I have a '76 c20 that was already ls 5.3 swapped when I bought it (from 02 silverado). It was mated to a turbo 350. All works great but I want overdrive to off set the 3.73 gear rear. I picked up an '02 silverado 4l60e trans and converter.
Will the flex plate in my current setup work for the swap? I think I read some spacer plate had to be used to swap the 5.3 to the turbo 350 but not really sure. I'm just trying to be prepped for the swap when I go to do it. I'm sure once I take it apart I'll have my answers but I rather be prepared and have other parts on hand if they will be needed.
Thanks for any info you guys can provide!
FYI, I did one ls swap with trans in my '85 c10, but I had the complete motor and trans from the salvaged truck so I didn't have to do anything odd.

 

[Ricko1966]

Is it carbureated or injected,what if any computer are you running?

 

[cjdock]

Stock pcm. I can tune it using tunerpro. Stock 5.3 with stock fuel injection.

 

[Ricko1966]

If it was me,I'd buy a flexplate and torque converter hardware for a 2001 Silverado just in case,and swap my 01 4l60e onto my 2001 5.3 and set my shift points in my computer. We can tell you the flex plate will work,but what if it doesn't? We didn't build it and no one knows for sure what P.O. did.

 

[cjdock]

If it was me,I'd buy a flexplate and torque converter hardware for a 2001 Silverado just in case,and swap my 01 4l60e onto my 2001 5.3 and set my shift points in my computer. We can tell you the flex plate will work,but what if it doesn't? We didn't build it and no one knows for sure what P.O. did.

Good points for sure. Thx!

 

[TotalyHucked]

Yeah IIRC you have to change the flexplate to adapt to the TH350 plus a spacer I think. So like Rick said, I'd just go ahead and buy a fresh '02 flexplate and new bolts and call it good. Might have to swap the starter too depending on tooth count. I'm not sure on that one, I've only ever swapped the LS with the 4L60 or 80 already with it as well

 

[cjdock]

Yeah IIRC you have to change the flexplate to adapt to the TH350 plus a spacer I think. So like Rick said, I'd just go ahead and buy a fresh '02 flexplate and new bolts and call it good. Might have to swap the starter too depending on tooth count. I'm not sure on that one, I've only ever swapped the LS with the 4L60 or 80 already with it as well

Thanks, that is what I will do for sure. Trans mount is the only other consideration. On my '85 swap I did do the trans mount just to make dual exhaust easier. ( two humps in the new trans mount versus one in the stock one. ) Though on the '76 the trans mount already has the 2 humps in it. I'm guessing I might be able to just move it on the frame rails to line it up to the new trans.

 

[TotalyHucked]

Probably so. I used a Tejas Steelworks trans crossmember on my '85 for exhaust clearance. There's several styles of original xmembers in the '73-80 trucks, especially if you have the one with the big humps, I wouldn't change it either.