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Have a few questions on subtle differences noticed between an original 5.3 flexplate and motor mounts. I'm dropping a 6.0 in place of an original FF 5.3 in an '04 Tahoe. Picture shows the removed 5.3 with flexplate still installed and the flexplate on the ground is from an lq4 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?
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?
On the motor mounts I purchased the heat shielding is different from old to new. The new ones were bought on 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?
Thanks in advance.
Motor mounts are the same and as far as I know all the flexplates that are dished (from 4.8, 5.3 and 6.0's with 4l60/65/70 transmissions) are the same.
New bolts are cheap insurance, and although the bolts go all the way through the crank, the reluctor wheel is right on the other side, so the chance of leak through is small, blue loctite at a minimum. Although, Permatex just came out with that new Orange flavor, the holding power of Red, but the removability of Blue. New GM bolts do come with a thread sealant thought, so YMMV.
Thank you for the replies. On the flexplates, are they functionally equivalent even though they look different, with the relief "windows?" And yes the one leaning against came from a 6.0LQ4 & 4L65e combo in a Yukon Denali. Flip a coin for which one goes back in?
I did not do a good job explaining my question on the motor mount difference. I ordered the exact part # that GM calls out for my vehicle, part # 25828247. The new ones have a different heat shield config as shown, vs. the '04 original ones that were installed when the Tahoe was built. Has GM changed or updated factory motor mount heat shields over the years? Is this what new factory GM motor mounts look like now vs 2004 vintage? Thanks again all.
Top flexplate is your average 4L60e flexplate.
Bottom flexplate is from a 6.0/4L65e combo like in an LQ9.
The difference in motor mounts is from the difference in vehicles they were made for.
Would you happen to know the rationale why GM had a different flexplate for the 4L60e vs the 4L65e trans? For how the bean counters run GM, there must've been a reason for them to develop/use a different flexplate for the two applications.
I think the flexplate bolts need sealant on them because they thread to the back side of the reluctor wheel on the crank. What sealant is the right stuff for these bolts? Also wondering the same question for an oil pressure sending unit, and coolant temp sending unit.
Motor mounts I guess I'd have to stop by a dealer and ask for a 25828247 and see what they bring out to compare the ones I have with the different style heat shield. Thanks.
Would you happen to know the rationale why GM had a different flexplate for the 4L60e vs the 4L65e trans? For how the bean counters run GM, there must've been a reason for them to develop/use a different flexplate for the two applications.
I think the flexplate bolts need sealant on them because they thread to the back side of the reluctor wheel on the crank. What sealant is the right stuff for these bolts? Also wondering the same question for an oil pressure sending unit, and coolant temp sending unit.
Motor mounts I guess I'd have to stop by a dealer and ask for a 25828247 and see what they bring out to compare the ones I have with the different style heat shield. Thanks.
Rigidity.
The later style mounts with the better heat shield are a better design. I don't think I'd waste my time investigating. Chances are, they were just updated and the old ones phased out/superseded.
I think the flexplate bolts need sealant on them because they thread to the back side of the reluctor wheel on the crank. What sealant is the right stuff for these bolts? Also wondering the same question for an oil pressure sending unit, and coolant temp sending unit.
As theunderlord posted...
The manual (attached below) calls for Threadlock on the flywheel bolts
"Apply threadlock GM P/N 12345385 or equivalent to the
threads of the flywheel bolts."
Red Loctite is probably best... I have used blue with no issues.
For the Oil Pressure sensor the manual says...
"Apply sealant GM P/N 12346004 or equivalent to the
threads of the oil pressure sensor." which is a liquid PTFE
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5.3 --> 6.0 Flexplate & motor mount differences 
