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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: medually on January 22, 2009, 04:35:59 pm

Title: Can you fit a 6 speed auto into.......
Post by: medually on January 22, 2009, 04:35:59 pm

I am looking at the possibility of doing a tran swap from TH400 454 to later model 5 or 6 speed auto in a 1988 C3500 Dually Crew Cab....has anyone done this or have any suggestions were to start looking

Title: Re: Can you fit a 6 speed auto into.......
Post by: choptop on January 22, 2009, 05:04:18 pm

They put the Allison 1000 behind the 8.1 already, so it should be hard to bolt up. The problem may be the tranny tunnel and the tcm for it. The best upgrade in my opinion would be a 4l80e. The Allison is a very expensive and heavy tranny. Could buy a 4l80 built extra tough for what the Allison costs and the Allison is really only built for 300-350 hp. People think they will handle more, but I worked for an Allison dealer and have proof that they wont.

Title: Re: Can you fit a 6 speed auto into.......
Post by: medually on January 22, 2009, 05:24:31 pm

hey thanks for that suggestion....any idea what the 4l80e cost over there.....I have a friend in Seattle who would be able to arrange shipping

Title: Re: Can you fit a 6 speed auto into.......
Post by: eventhorizon66 on January 22, 2009, 06:01:55 pm

I did a search on the LKQ network.  There is a 4L80E from a 2004 Chevy Van with 60K mi for $1150, another from a 1999 Chevy 2500 with 93K mi for $800 both in Portland, OR.  Keep in mind you must either hack a factory TCM or run an aftermarket TCM like this one (http://www.hgmelectronics.com/products/compushift).

Title: Re: Can you fit a 6 speed auto into.......
Post by: choptop on January 22, 2009, 08:42:49 pm

I know the aftermarket tcm is high, but unless you are an elctronics wizz, the cost would be worth it. I have the ability to build my own harnesses with the right schematic, but would even consider the aftermarket one.

Title: Re: Can you fit a 6 speed auto into.......
Post by: medually on January 22, 2009, 10:02:45 pm

hey thanks choptop...

Title: Re: Can you fit a 6 speed auto into.......
Post by: VileZambonie on January 22, 2009, 10:35:24 pm

TCI also makes a standalone controller

http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=TC&Product_Code=377500&Category_Code=ELEC

Or you can use a factory ECM and harness with appropriate sensors

Or make it a non computer controlled unit. Transgo has the goods

Title: Re: Can you fit a 6 speed auto into.......
Post by: eventhorizon66 on January 22, 2009, 10:53:13 pm

Quote from: VileZambonie on January 22, 2009, 10:35:24 pm

Or make it a non computer controlled unit. Transgo has the goods

This, I did not know.  You mean without going to full manual shifts?  I'll have to look into this.

Nevermind, I can see you are talking about full manual valvebody.

Title: Re: Can you fit a 6 speed auto into.......
Post by: Fishtail8 on January 23, 2009, 04:47:30 pm

I did a 4L80E swap in mine with the Compushift. The first time I tried this swap, it resulted in the previous truck being down for 2 yrs while the guy I had building the harness got it all figured out. With the Compushift you have control over alot of the functions of the trans. It dropped the cruise rpm's by 1000 on the highway once the converter locks.  I say 80E and Compushift...

Title: Re: Can you fit a 6 speed auto into.......
Post by: Captkaos on January 23, 2009, 05:22:49 pm

Fishtail8,  I have been looking for someone with real experience with the compushift.  I heard they are pretty good.  The price is the kicker.

Title: Re: Can you fit a 6 speed auto into.......
Post by: Fishtail8 on January 23, 2009, 07:31:52 pm

I can tell ya Captkaos, I'm very happy with it.