L31/6L80e

GoToGuy

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What is trans "bushing?" Rather than hog the mount holes out. Could you just slide the trans crossmember forward or back an inch or two and 4 new holes? Trans changeouts or swaps I've tried not mess with trans location or attachment. Just a thought.
 

97Centurion

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Well? How did yesterday go?
It went fairly well! The transmission shifted through all gears, however, there is some tweaking I need to do with the upshift from 2nd to 3rd, and all the downshifts. 1st gear is dramatically different and definitely the stump pulling gear. I find that with these sbc torque values a little lower in the rpm band than the LS/LT motors, it's almost as if the 6L makes better use of the power band than the 4L.
 

97Centurion

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What is trans "bushing?" Rather than hog the mount holes out. Could you just slide the trans crossmember forward or back an inch or two and 4 new holes? Trans changeouts or swaps I've tried not mess with trans location or attachment. Just a thought.
I've considered this as well before going the route I ended up going. Simply, it was easier to move the mount back rather than drilling new holes through the frame. The 6L is VERY close in length to the 4L and did not require any further modification other than the trans mount (in my case, 'lest ye move the crossmember itself back). So virtually it is dang near a perfect fit.
 

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stutaeng

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Nice job! You've pioneered another "mod" for the GMT 400! LOL

What gear ratio does your truck have? I've read some comparisons on 4L vs 6L on the ls1tech forums and some guys say the fist gear of the 6L is too steep (maybe for a f-body?) I don't know.

I did recently buy a passenger 3500 van with the 6.0/6L90e/3.42, so I'm getting used to the transmission...my other trucks have the 4L80e/4.10 and I think I like the 4L80 more, but I think it's the rear gearing difference and the fact that the van is a big, heavy vehicle. The vans only come with 3.42, but the HD trucks came with 3.73s.

Also, what was the mileage on the transmission? Those seem to fail at around a certain mileage and send metal into the transmission and can cause a lot of damage. Maybe around the 150k mark? An aftermarket converter solves the problem though.

Let us know how you like it. Very interesante mod!
 

CrustyJunker

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Nice job! You've pioneered another "mod" for the GMT 400! LOL

What gear ratio does your truck have? I've read some comparisons on 4L vs 6L on the ls1tech forums and some guys say the fist gear of the 6L is too steep (maybe for a f-body?) I don't know.

I did recently buy a passenger 3500 van with the 6.0/6L90e/3.42, so I'm getting used to the transmission...my other trucks have the 4L80e/4.10 and I think I like the 4L80 more, but I think it's the rear gearing difference and the fact that the van is a big, heavy vehicle. The vans only come with 3.42, but the HD trucks came with 3.73s.
Don't mean to hijack, but have you considered a trans tune? My brother-in-law got one through maybe Blackbear or maybe another popular outfit... I'd have to ask. He had a 5.3/6L80E/3.08 in a pickup. Not sure what the shift schedule is like in your van...But his seemed to want to get into high gear as soon as possible. It would short-shift to 3rd gear just leaving a stoplight and going around a corner. Tune made a night and day difference just riding in it.
 

sync

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Once you're done working out any bugs. A confined list of everything you needed to do, wiring diagrams, etc would be really helpful.

One question I have right off the bat, does the 6L80 work with our factory shifters?
 

stutaeng

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Don't mean to hijack, but have you considered a trans tune? My brother-in-law got one through maybe Blackbear or maybe another popular outfit... I'd have to ask. He had a 5.3/6L80E/3.08 in a pickup. Not sure what the shift schedule is like in your van...But his seemed to want to get into high gear as soon as possible. It would short-shift to 3rd gear just leaving a stoplight and going around a corner. Tune made a night and day difference just riding in it.
Thanks. Yes, that's what I was thinking. Maybe regear to 3.73s since long term plan was to buy a travel trailer to tow with it. I just bought it, so only have driven it a few times with the family.

I was going to purchase HP Tuners to mess with my other project truck today, but then realized it doesn't support the van (2020 model.) Not sure what's up with that. I may to call them and ask.

I've seen some transmission guys make some changes to the tune tables to help correct some issues with the transmission (in addition to replacing the TC and doing the Transgo/Sonnax valve upgrades.) I think it is related to the DOD and keeping the torque converters from failing again. I don't know anything about tuning though.

I don't think the 2500/3500 had DOD though (but do have VVT)? at least not in the Gen IV.

Anyway, back to the OP...
 

97Centurion

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Once you're done working out any bugs. A confined list of everything you needed to do, wiring diagrams, etc would be really helpful.

One question I have right off the bat, does the 6L80 work with our factory shifters?
Yeppers, as stated, once complete, I'll have everything together and do a follow up post.

As far as the shifter in general, yes it does work. It pops right onto the shifter linkage. My 6L did not have any of the miscellaneous bracketry, so I fabricated my own shifter bracket using 1/8" angle iron and cutting off the C-shaped part (pictured) of the 4L's and welded it together.
 

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