'88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

So I found an '88 4x4 dually that I am converting to a fleetside and I have a few questions and need resources to find what exactly I need to do to also get the trans swap to the 4L80E done seamlessly!

I have searched on here and various other site, but I haven't come up with much in depth details! I want to find out a few things before I jump head first into this...even though the trans and converter are already being built...

1. Is it possible to find refurb'd OEM Transmission control modules from 1991 or is it going to be easier to just run the new GMPP 19257661 Stand-alone TCU or even the TCI EZTCU? I guess another question would be, is the 1991 truck PCM a single computer that runs engine and transmission functions or are they separate? My only experience is with my old 1990 V3500 Crew Cab SRW (Turbo 400).

2. The whole shift lever assembly in the column, as far as the 4-speed indicator and all associated parts and hardware need to be sourced from a 1991 column or a 700-R4 column, has anyone made a list of the entire group of parts needed?

3. The main difference with external linkage is gonig to be finding a 4L80E shift linkage and that is it, correct?



Thanks in advance guys!

Steve

Re: '88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

^^^^^^^

Re: '88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

Assuming yours is a throttle body, find a computer and wiring harness from '92 - '95, set up for the 4L80E. Shouldn't be too hard, there were tons of 'em made. I bought a '95 with a dead 350 for $500, got the 4L80E, TBI wiring harness a good cab/front clip and $200 cash when I scrapped it.
All of my 4L80E linkages are cable, make sure you get the steering column that corresponds to it. I'm sure there are mechanical linkages for it, the shifter itself works just like other GM trannies.

Re: '88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

Mine is a TBI truck, so I will assume an engine harness and PCM from a '91 or newer with a 4L80E will suffice...as long as the harness and trans case are between a '91 and '95 I will be fine, since the later models lost the tone wheel for the Output Speed Sensor...the case I am using is a newer case with the centeral lubrication updates...
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Re: '88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

You can get a harness from www.fuelinjectionconnection.com for $245 that is new and set up to run the 4L60/80E. If you are running TBI already it should be a no brainer. Get an ECM that was from a TBI/4L60/80E truck, and it should be plug and play. Robert can probably set you up with that, too.

I would think you can use your existing column; I am using the original one in my '74 to shift a 700R4, and it grabs all of the gears. The quadrant is in the cluster, and is held in place with 2 screws, once you get the cluster out.

I used teh FIC harness in my swap, and I thought it was a quality piece. I am very pleasd. They should be somewhat local to you, Adam. They are in Golden.

Re: '88 1-Ton Crew Dually to SRW & T-400 to 4L80E Conversion
 

Thank you for the link! I just spoke with Robert and my transmission builder, it looks like this is going to be a very simple project to complete!

1. New Engine/Transmission Harness for '94-'95 TBI/'93+ 4L80E will be a direct plug in setup! ($305.00)

2. 16196395/16197427 PCM purchased from Robert at www.fuelinjectionconnection will include all programming for the 454 TBI/4L80E and the E-Prom chip for the truck! ($140.00)

3. All I need is a DRAC module to compute the 40 pulses for the VSS (Vehicle Speed Sensor) signal. I can use either an adjustable unit from www.jagsthatrun.com or he can supply one for my specific tire size/gear ratio ($110.00) or I can get one local, which I will probably do since we know and have worked with the owners of Nevada Speedometer.

The only things you need to worry about are as follows:

1. The internal transmission harness of the transmission
- The pre-'94 units had the old style harness plug with a bolt to secure the external harness to the transmission's internal harness, you I have to make sure the trans is built with the newer style harness.

2. When you select your transmission, you need to be careful with the older trucks. You need to make sure your transmission has BOTH the Input Speed Sensor AND the Output Speed Sensor. The newer TBI trucks with the 241 t-case had the Output Speed Sensor on the tailshaft of the t-case, so you need to convert the transmission to include the sensor on the side. (All 4L80E cases had provisions for both sensors, but the later trucks did not include the sensor) and you will have to make sure the transmission gets built with the reluctor wheel installed into the trans.