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4L80 swap

valyidol

Active Member
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Location
Russia, Moscow
Hello
I have 1988 Squerebody Suburban 6.2 diesel TH400. I'd like to install 4L80.
I have a 4L80 from a 1995 Suburban 7.4L with a torque of 24204836. I know that for 6.5 diesel is used torque 24204835. What's the difference between 24204836 and 24205835?
And what is the simpler and cheaper way to make the 4L80 work? Should I use trucks wiring with DB2 IP? Or make the manual control? Or buy a universal TCM?
 

Will L.

Well-Known Member
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Boulder City Nv
I don’t know the part numbers. I can’t help with other options.
But, I can tell you the stall speed on the gas torque converter is way higher. You will be through, or almost through all the torque of the Diesel engine by the time the gas torque converter engages. It will feel weak& sluggish taking off. I believe it would cause the clutching to wear sooner. Do not use the gas converter.
You could get an aftermarket unit also, but definitely want it innthe range of the diesel converter.

If you use a regular tcm, you will need to get the harness for it also. I would probably just get the aftermarket one and you then have versatility in settings also. Far simpler and I believe their software allows for diagnostics easier when there is issues years down the road. https://leroydiesel.com/products/optishift-transmission-controller/
 

valyidol

Active Member
Messages
308
Reaction score
88
Location
Russia, Moscow
I don’t know the part numbers. I can’t help with other options.
But, I can tell you the stall speed on the gas torque converter is way higher. You will be through, or almost through all the torque of the Diesel engine by the time the gas torque converter engages. It will feel weak& sluggish taking off. I believe it would cause the clutching to wear sooner. Do not use the gas converter.
You could get an aftermarket unit also, but definitely want it innthe range of the diesel converter.

If you use a regular tcm, you will need to get the harness for it also. I would probably just get the aftermarket one and you then have versatility in settings also. Far simpler and I believe their software allows for diagnostics easier when there is issues years down the road. https://leroydiesel.com/products/optishift-transmission-controller/
Yes, I so it and I think about it. But $605.
 

Will L.

Well-Known Member
Messages
13,106
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18,466
Location
Boulder City Nv
I did a full manual control 4l80e in a car years ago. I would never do it again. When it shifts, it feels like you are in a low class race car, even when you are trying to drive smooth.

I just added the link to Leroy’s because I know he sells it, and never heard anything bad about that brand. There are others available, but do research before you buy, you don’t want something that has poor technical support.

If you can find a good tcm, and all the harness required- it might be cheaper. Finding the all parts where you are I am guessing is the he challenge. Keep in mind speedometer.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
10,294
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4,831
Location
ZEPHYRHILLS FL
I don’t know the part numbers. I can’t help with other options.
But, I can tell you the stall speed on the gas torque converter is way higher. You will be through, or almost through all the torque of the Diesel engine by the time the gas torque converter engages. It will feel weak& sluggish taking off. I believe it would cause the clutching to wear sooner. Do not use the gas converter.
You could get an aftermarket unit also, but definitely want it innthe range of the diesel converter.

If you use a regular tcm, you will need to get the harness for it also. I would probably just get the aftermarket one and you then have versatility in settings also. Far simpler and I believe their software allows for diagnostics easier when there is issues years down the road. https://leroydiesel.com/products/optishift-transmission-controller/
454 & the 6.5l converters interchange, it's the small block converters that flash up.

The 454 setup will work ok behind a 6.2l. Don't bother with factory tcm's to control it, stick to an aftermarket like the quickshift unit. You will have to add a tps so it knows throttle position, but getting a good engine speed signal to a tcm from your 6.2l will be difficult. Last I heard the speed pickup/oil pump drive units are getting scarce and very expensive when you do find one. And no tcm is going to shift that well without an engine speed signal.
 
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