Reading around online i have found plenty of contradictions, from saying i need extensions, to pilot sleeves, to i need nothing but to drill some holes!

From what i gather, the output of the crank on the early lq4 is the same as a SBC, and should make quite nicely with a 200r4.

I have read that my flex plate will either need to be redrilled, or use a 11.5" tq converter, or an adapter plate?

Is this the correct plate?

https://www.summitracing.com/parts/add-712500a

The build thats being started is an 89 caprice wagon.

 

I was contemplating the same thing and from what I read it will work fine with elongating the flywheel holes. I didn't stick with the trans so I can't confirm :/

 

So at advance adapters site on the above listed part i find this notice -
At first thought this would lead me to believe i can just without the spacer, but its saying not to use it at all? what the what?

 

Early long cranks have 0.400" length extra. If you could remove 0.400" and the rear main seal still work, you have a long crank. This puts the crank and bellhousing mating face of the block at the same relationship as a BBC/ SBC. The 4L80E was set up with a converter to mate to this, since it was used behind BBC, and 6.0 etc. After long cranks, they went to a spacer so a short crank LS could fit to a 4L80E etc.

A long crank can only run a flat LS flexplate. You probably already have one. No need to buy a spacer if you can use/buy a flat flexplate. Whether your converter pattern is close enough is the only question remaining.

If it is a short crank, a dished flexplate can be used with an LS transmission. Or a spacer and flat flexplate can be used to mate it to the non-LS depth transmissions like the 4L80E.

So figure out the converter pattern and you're good. The adapters companies sometimes explain things in ways that overcomplicate. You're on the right path.

 

This is perfect, THANK you.

Picking up the motor this weekend if all goes well, trying to plan it around a wedding im in.

knowing all this confirms the purchase honestly, so again, Thank you

 

I just did this swap, (2004 avalanche 5.3) swapped in a 1999 6.0L LQ4. The LQ4 crank IS LONGER by .400".
The 5.3 flexplate is dished and wont work with the LQ4 because the torque mounting bolts hit the rear cover of the engine.I ended up using the 6.0l flexplate.Elongated the holes, half a hole, flipped it over so the torque mounting holes are recessed,and then used 1/4" spacers on the 3 torque mounting bolts.

 

So I have read this thread and I couldn't find an exact answer to my situation.
I have a 1999 c1500 suburban with an LT style 4l60e trans with the 298mm torque converter. Well it just went out.
Anyway I was able to get a 4l60e out of a 2001 Sierra 1500 that has the LS style bellhousing with the 300mm torque converter.
Now should the torque converter just bolt right up to my flexplate or do i need to get a different one? And if so, then will I need to get a new starter as well?

 

Since you are basically going to a stock setup, just use a stock 99 and up flywheel and starter, if you don't have those parts already.

 

Hello! I have a question regarding the flexplate issues. I bought a 6.0l from a 2005 Yukon VIN digit 8 is U, the transmission was 4l60 all whell drive dish flexplate with 3 bolt mount to converter.
I install the motor in my 04 silverado using my same 4l80e converter and flywheel .the torque converter bolts are hitting the rear main seal bolts. Any suggestions? Thanks!

 

Put the Spacer on it inbetween the Flexplate and the Crank on that 2005 Engine, it would have been that way in the stock 2004 6.0l Engine with the 4L80E.


As to the above stuff, Long Crank 4.8l/6.0l you just use the factory Flat Flexplate that would have been on that Engine, slot 3 of the Holes in it and can run pretty much any Auto Transmission that was behind a SBC.

It's that simple.

 

While @the_merv is correct that you need a spacer between the flexplate and the crank on that setup (with a flat flexplate), it sounds like you have no space between the converter and the flexplate. This make me think the converter is not fully seated. The "plane" of the converter pads should be about 1" past the "plane" of the bell housing edge. This will give you a huge gap between the flexplate and converter, which the spacer solves.
This Sticky in the Automatic Transmission section details it:
https://ls1tech.com/forums/automatic...s-spacers.html

 

The way I'm reading his post the Convertor Bolts are hitting the back of the Engine, which has be thinking he didn't use the Spacer.
If that is so then the Convertor won't be fully seated in the Pump either.

Which yes, if the Convertor was fully seated there'd be atleast a half inch there, more like almost 5/8"..

 

I see someone in a similar situation as myself asked but did not receive an answer. I have a 97 c1500 5.7L that I’d like to mate a 2007 c1500 5.3L 4l60e trans to. I’m swapping the valve body’s with all solenoids and harness/connector from the 97 to the 07. Still unsure if the pump will be ok to leave alone. And I’m assuming I would just leave the ISS in just not used or connected. I know the bell housings will be fine just no top bolt used. But would the converter bolt right up to my stock flex plate? Or will a spacer between the bellhousing and block be needed? Or that plus a new flex plate? All the online options that specifically bolt a “Ls” style trans to a gen 2 sbc are out of stock or discontinued. What should I be concerned with or on the lookout for?