Transmission swap help/instructions

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smoynier

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Hey all, I have a 96 GMC 1500 with 5.7l. I want to swap my man trans for a 4l60-e.
How difficult? What do i need? Has anyone wrote up an instructional on this?

Thanks in advance.
 

stutaeng

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I don't claim to be an expert, but here's my advice:

1. You'll need to adjust your transmission crossmember to the location of the new transmission. There may be holes already on the frame for this? Driveshaft my need to adjusted or swapped too?

2. You need to figure out the wiring difference between the auto and manual. Maybe you'll need a complete wiring harness that has that big connector that goes into the transmission on the 4L60e.

3. You need to reflash your ECU to recognize and operate the auto transmission. Or a matching ECU for the auto.

4. I suppose it goes without saying that the clutch pedal, etc. needs to be removed, unless you want to leave it as a theft deterrent?

Make sure you get the correct 4L60e for your year/ECU. Look into the sticky link that talks about differences in years.

And note there's a TSB for some wiring grounds that affects some 1996 models.

There's plenty of guys going manual, should be the opposite in your case, minus electronics.
 

Nad_Yvalhosert

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There's also the necessary closing of the hole in the floor.
Dont forget to get a shifter. If you go the OE route, you'll need an entire new column, shifter cable, and bracket on the tranny housing.
If you remove the clutch pedal, how about installing the larger Auto trans brake pedal?
Is your truck a 2wd or 4x4? Theres a bolt-on mount/spacer in between the auto trans and the t-case...

It would be best to get a donor truck for all the correct parts.
 

Nad_Yvalhosert

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Lastly, if you have a 2wd the 31 spline driveshaft yoke wont match the 27 spline 4L60 output shaft.
If you have a 4x4, your OE driveshaft is fine.
Hopefully the tranny comes with a dipstick and tube.
And either clean out or bypass the OE cooler in the radiator, then purchase the cooler lines. I also suggest you install an external auxiliary cooler.
 
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gwolf

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Listen to Schurkey before it's to late. With these trucks it's best to just buy what you want up front, unless you like perpetual frustration.
 

Nad_Yvalhosert

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If your truck is 4wd the transfer case input will have to be the same 27 spline.
Not if it's a manual tranny. The manual, like the TH400 use a 31 spline output. Meaning the t-case has a 31 spline input shaft. But all 1500's have 27 spline outputs.

So O.P. will need a different t-case. Ask me how I know...
 
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