Engine swap '04 Tahoe 5.3 to 6.0

mattt

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I figured I'd start an engine swap thread for future reference and for others who want to do the swap in the future. I'm about half way thru the swap process. The old still running well 335k miles 5.3 that leaked oil prodigiously is out, and on a tire and pallet. The 6.0 is on the stand and waiting to go in while I clean up the engine bay with everything out.

The 6.0 was sourced from a Pick Your Part junkyard from an 04 Yukon Denali LQ4 with unknown miles. I ordered a complete LS "rebuild kit" from WS6 Store that came referred on LS1Tech.com. Everything looked okay internally but the unknown factor led to a full rebuild, .020" O/S flat top LQ9 pistons, full cylinder head rebuild & bowl blended ports, w/ Smith Bros trunnion upgrade. The builder surmised the CR would be 10.3:1 or thereabouts after the machine work on the heads and block, along with the head gasket used. Summit Racing truck cam 8718R1, small-ish side to keep it more sleeper, and be daily driver & tow rig friendly. LS6 valve springs. Luckily the LQ4 I started with has the later Gen 4 rods with removable piston pins w/ circlips. Had those "rebuilt" with new pin bushings and the .002? O/S bearing. Crank and block was checked, decked, and refurb'd. New oil pump, bearings, hardware, etc. I had the long block professionally assembled by a local engine builder. New GM knock sensors & harness, new GM motor mounts

I have a couple questions on subtle differences noticed between the original 5.3 flexplate and motor mounts. Picture 1 shows the 5.3 with flexplate still installed and the flexplate that was on the 6.0, that came from an 04 Yukon Denali. Does it matter which one is used with the 6.0 and the original Tahoe trans? Bolt patterns seem to be the same, but the "window" cut outs are a bit different. Is there a difference in flexplates from 5.3 to 6.0 or 4L60 to 4L65? I know from my Ford days, there are different offsets & imbalance in Ford flexplates depending on engine family and year model. Is that the same case with the 5.3, 6.0?
Is there a strong reason to not re-use either of these used flexplates? What about flexplate hardware....is it single use like TTY head bolts or is it acceptable to re-use flexplate bolts?

With the motor mounts the heat shielding is different from old to new. The new ones were bought from Ebay from a seller in Ohio for $41 each that claims these are new, un-used take off GM motor mounts. The part # on the sticker is correct. Did GM change the heat shield on later year motor mounts? My original 04 motor mounts have the straight tin, metal heat shield as opposed to the wrap metal foil heat shield seen in the picture? Any GM motor mount experts can say by looking at the pic?



mmount2.JPGmmount.JPGmmount0.JPGmmount1.JPG
 
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Mudsport96

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I am pretty sure 60 to 65e there shouldn't be any offset difference. Maybe someone that knows that swap better will post. As for balance that doesnt matter since you opted for different pistons and such, the factory balance is out the window anyway
 

Tonyrodz

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I'd recommend getting a better flywheel. They tend to crack. It's not the usual, but I've had to replace 2--both oems.
 

iamdub

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Does it matter which one is used with the 6.0 and the original Tahoe trans? Bolt patterns seem to be the same, but the "window" cut outs are a bit different. Is there a difference in flexplates from 5.3 to 6.0 or 4L60 to 4L65?

In the earlier models, pre-dating yours, there was a flat flex plate and spacer to make up for a .400" shorter crankshaft. Both of your flex plates should have the same amount of dish and the crankshaft should have the same reveal between the two engines. My initial thought is to use the one from the 6.0. Measure where the 5.3 flex plate is in relation to the bellhousing mounting surface and compare it with the 6.0's flex plate mocked up to the 6.0. I bet they're the same.


Is there a strong reason to not re-use either of these used flexplates?

As Tony mentioned, some people have issues with them cracking. Personally, I don't know of it as being a "common" problem, at least not on stock vehicles. I can see F-bodies, etc. cracking them. I'm inclined to think it might be due to hard use/racing and/or worn trans input bearings allowing radial movement in the torque converter.


What about flexplate hardware....is it single use like TTY head bolts or is it acceptable to re-use flexplate bolts?

You can re-use those bolts if they're in good shape. They're not TTY. Mind the sealant/thread locker.


With the motor mounts the heat shielding is different from old to new. The new ones were bought from Ebay from a seller in Ohio for $41 each that claims these are new, un-used take off GM motor mounts. The part # on the sticker is correct. Did GM change the heat shield on later year motor mounts? My original 04 motor mounts have the straight tin, metal heat shield as opposed to the wrap metal foil heat shield seen in the picture? Any GM motor mount experts can say by looking at the pic?

If you got genuine GM OE mounts for $41 each- score! The heat shield did get updated at some point, but I thought it was later, for the Gen4. If the bolt holes, critical dimensions, etc. all match up, they're good to go. Actually, the newer design looks more compact so it should fit better.
 

rockola1971

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Flexplate is the same for 60e/65e tranny AND 5.3L and 6.0L (Except for the first 2 model years of the 6.0L which are 99-00. The reason why 99-00 flywheel is not compatible with the 5.3l is because the 99-00 6.0L crank snout at the rear was longer. Otherwise 4.8L,5.3L,6.0L,6.2L are all compatible. (Excluding transverse Front Wheel Drive cars)
 

tRidiot

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Flexplate is the same for 60e/65e tranny AND 5.3L and 6.0L (Except for the first 2 model years of the 6.0L which are 99-00. The reason why 99-00 flywheel is not compatible with the 5.3l is because the 99-00 6.0L crank snout at the rear was longer. Otherwise 4.8L,5.3L,6.0L,6.2L are all compatible. (Excluding transverse Front Wheel Drive cars)

Excellent information that should be put into an easy to find place - I think this came up during my motor swap, too, and took some research to track down.
 
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mattt

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In the earlier models, pre-dating yours, there was a flat flex plate and spacer to make up for a .400" shorter crankshaft. Both of your flex plates should have the same amount of dish and the crankshaft should have the same reveal between the two engines. My initial thought is to use the one from the 6.0. Measure where the 5.3 flex plate is in relation to the bellhousing mounting surface and compare it with the 6.0's flex plate mocked up to the 6.0. I bet they're the same.
They are the same dimensionally from what I see measuring. From what I was told on LS1Tech for some reason, unknown to me, GM used a different flexplate for the 6.0/4L65e vs the 5.3/4L60e configuration. Yes I've seen one of the flat flexplates on the early "iron head" lq4 and the crank difference is an issue if you want to stuff that engine in front of a 4L60 or 4L65. It won't work. That early lq4 only works with a 4L80 behind it.

As Tony mentioned, some people have issues with them cracking. Personally, I don't know of it as being a "common" problem, at least not on stock vehicles. I can see F-bodies, etc. cracking them. I'm inclined to think it might be due to hard use/racing and/or worn trans input bearings allowing radial movement in the torque converter.




You can re-use those bolts if they're in good shape. They're not TTY. Mind the sealant/thread locker.

Cool thank you for confirming on the bolts. Would you have a recommendation for sealant for those bolts, the oil pressure sending unit, and the coolant temp sending unit? I'd like to replace the O-rings on the other sensors as well but GM doesn't offer the O-rings separately. Gonna have to go on the hunt. I'll check the flexplate for cracks, but I think I'm gonna run the original 6.0 plate.
If you got genuine GM OE mounts for $41 each- score! The heat shield did get updated at some point, but I thought it was later, for the Gen4. If the bolt holes, critical dimensions, etc. all match up, they're good to go. Actually, the newer design looks more compact so it should fit better.
They are dimensionally the exact same, just the heat shield is different. Already bolted them up and all is good. I may run by a dealer and ask for a 25828247 and see what comes out just to confirm that part # looks like the ones I received. I suppose it's not out of the question that in 18 years GM changed/updated the heat shielding on the motor mount. Yeah, they seem legit and the seller has 100% positive feedback. I'll find out over time. Here is the listing for them. https://www.ebay.com/itm/313323450385?hash=item48f3887011:g:oUkAAOSw~8FfxS4E
 
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iamdub

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They are the same dimensionally from what I see measuring. From what I was told on LS1Tech for some reason, unknown to me, GM used a different flexplate for the 6.0/4L65e vs the 5.3/4L60e configuration. Yes I've seen one of the flat flexplates on the early "iron head" lq4 and the crank difference is an issue if you want to stuff that engine in front of a 4L60 or 4L65. It won't work. That early lq4 only works with a 4L80 behind it.

Your stuff is all within the same generation so you're good to go.


Cool thank you for confirming on the bolts. Would you have a recommendation for sealant for those bolts, the oil pressure sending unit, and the coolant temp sending unit? I'd like to replace the O-rings on the other sensors as well but GM doesn't offer the O-rings separately. Gonna have to go on the hunt. I'll check the flexplate for cracks, but I think I'm gonna run the original 6.0 plate.

I've always used a healthy coat of blue Loctite on the threads. Never a problem. Some use red, but blue has always held just fine, especially with all the threads coated. Using red might cause problems should they ever need to be removed. Since sealing is also part of the reason for using it, you wanna use a lot. You don't wanna use a lot of red. Be sure you clean the holes in the crank flange very well- brake clean, wire "pipe cleaner" brush, dry with compressed air, more brake clean, etc. I've never reused oil pressure and coolant temp sensors and the new replacements come with dry threadlocker on them. I'd imagine a similar sealant would be fine, but don't completely coat the threads since the sensor might use the block as a ground.
 
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mattt

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Going thru things today since my buddy wasn't able to help drop the long block in the Tahoe today. I was looking at part of the engine wiring harness and a question came up. Is the engine harness all one piece, including the lower portion that wraps around the oil pan up front and grabs the starter, oil pan sensor, A/C compressor? Or is that lower part sub-harness separable and connected to the main harness somewhere with a connector? Asking because if it were replaceable, I'd be considering replacement on that lower part.

I've dealt previously with Mustang 5.0 EFI harnesses, and there are 3 separate harnesses that inter-connect with Q/D plugs making up the complete engine harness.

Is the '04 Tahoe engine harness all one piece or are there possibly connection points that I missed? Thanks.
 

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