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Old 06-04-2019, 02:22 PM   #1
SCOTI
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Diesel 4l80e to Squarebody 7.4l/TBI swap?

I understand the OBS style HD trucks came w/stand alone trans controllers on the diesel equipped 1-ton trucks through about /95.

Is this correct?
What would it take to transplant the 4l80e from a /93 6.5 1-ton behind the 7.4l TBI BBC powering my Squarebody CC Dually??

Experienced answers would be appreciated.
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Cubic inches is like Indiana Jones with a cheap pistol....
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Old 06-05-2019, 06:13 AM   #2
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

IIRC 4l80s are the same between trucks n motors, save for the converter. This is what I’ve read and have been told. Shifting/controlling what not is done by the ECM....
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Old 06-20-2019, 11:20 AM   #3
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

Quote:
Originally Posted by b454rat View Post
IIRC 4l80s are the same between trucks n motors, save for the converter. This is what I’ve read and have been told. Shifting/controlling what not is done by the ECM....
I recall reading that 'some' early OBS trucks w/diesels used a stand alone TCM for the OD autos.

I found a 93 dually w/a 6.5/4l80e. The trans was supposedly recently rebuilt but then the motor went bad. The guy doesn't want to throw any more coin @ it & is parting it out. If all I need is a convertor for a gas engine, then that definitely plays into the cost effectiveness of a TH400 to 4l80e swap. But, if I have to get a TCM, it puts the swap closer to 1k & not as good of a deal.
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Building a small, high rpm engine
with the perfect bore, stroke and rod ratio is very impressive...
like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar.

Cubic inches is like Indiana Jones with a cheap pistol....

Last edited by SCOTI; 06-20-2019 at 12:18 PM.
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Old 06-20-2019, 02:37 PM   #4
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

I believe the 454 and the diesels used the same low stall convertor in these years. Seems it was only the 4.3/305/350 that got the higher stall speed, if I remember correctly
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Old 06-20-2019, 07:32 PM   #5
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

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I believe the 454 and the diesels used the same low stall convertor in these years. Seems it was only the 4.3/305/350 that got the higher stall speed, if I remember correctly
I've seen lots of internet guess's saying yes & no. I searched a bunch & found more info saying most were controlled off the ECM. I could have swore I read it somewhere here about the early diesels using a stand-alone set-up. I found some H1's did.... not much about diesels though.
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Building a small, high rpm engine
with the perfect bore, stroke and rod ratio is very impressive...
like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar.

Cubic inches is like Indiana Jones with a cheap pistol....
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Old 06-20-2019, 08:14 PM   #6
44th Miss Inf
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

I'm working on a setup to use a later computer(99 up) to control the 4l80. I believe I have it sorted, just need to find me a good trans or rebuildable core.

I believe most aftermarket companies list the needed convertor as GM81
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Old 06-20-2019, 08:44 PM   #7
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

The early 6.5/4L80 were stand alone, but when tried behind a 350 or gas carb'd engine, the convertor didn't lock up. It was tried on the 454SS site, dunno why it wouldn't work. I was gonna do same thing, but was told no lock up and then just gave up on the swap lol....
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Old 06-20-2019, 10:27 PM   #8
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

Quote:
Originally Posted by b454rat View Post
The early 6.5/4L80 were stand alone, but when tried behind a 350 or gas carb'd engine, the convertor didn't lock up. It was tried on the 454SS site, dunno why it wouldn't work. I was gonna do same thing, but was told no lock up and then just gave up on the swap lol....
Hhmm..... Seems a simple 12v solenoid to switch the lock-up feature would solve that.
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Building a small, high rpm engine
with the perfect bore, stroke and rod ratio is very impressive...
like a highly skilled Morrocan sword fighter with a Damascus Steel Scimitar.

Cubic inches is like Indiana Jones with a cheap pistol....
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Old 06-20-2019, 10:51 PM   #9
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Re: Diesel 4l80e to Squarebody 7.4l/TBI swap?

Through 1994 the 6.x diesels used the cable throttle DB2 injection pump with no ECM. These had a stand alone TCM for the 4L60E & 4L80E. They can be adapted to gasoline engine use. You need to do a handful of internal changes. No I don't know what those changes were but there are some differences between the Diesel 4L80E and the Gasoline 4L80E. It may be as involved as changing the Diesel valve body out with a Gasoline valve body but I'm not sure.
You will definitely need a torque converter that suits the 7.4L RPM, torque, and HP curve.

1995 & later are drive by wire DS4 pumps with the TCM integrated with the ECM. These all in one controllers were called a PCM.
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