4L60E to Th400 swap 94 ecsb

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94chevc1500

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Hello I have a 94 2wd ecsb and the original 4L60e in it has gone to all forward gears no reverse no park and the pan is full of shreds... Can't really afford to grab another 4L60E right now but I have 2 good th400S the one I want to use is out of a 91 c2500 2wd I was wondering if anyone has done the same and if so what was the process?
 

Erik the Awful

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I think your driveshaft will be too short. For the cost of having a driveshaft lengthened, you can probably score a 4L60e from a friend with a truck parked in their field.
 

stutaeng

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I really don't know how to handle the electronics for that swap, but you may want to look into an 8 lug 88-90 truck for parts; those had the TBI/TH400 from the factory. Different ECU? Or reflash existing ECU for the different transmission?

"Some" 1500 of the same years also got the TH400, but seems like they were the fleet or work truck plain trim and maybe made less of them?

88-90 vs your 94 electrical differences? If any?

Also, are the TH400s you have electrical or mechanical seed sensor? I'm pretty sure your 94 requires electrical.

Yeah, the driveshaft will be too short. Again, maybe a stock driveshaft from those years I listed may work. The yoke between the transmission is 27 vs 32 spline. Transmission crossmember slides back a few inches. Drill new holes if factory holes aren't there already.

Maybe check out the F-body forums. I've seen th400s swapped into those.
 
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94chevc1500

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I do have the driveshaft out of the donor truckwhich was a 91 single cab c2500.
My stock one definently won't work I've got them out and next to each other on the ground.
Does the tbi have to see a vss signal? Atleast to operate correctly? If so I probably will be just going and finding a 4L60e because this seems to be not so popular of a swap
 

Erik the Awful

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Also, are the TH400s you have electrical or mechanical seed sensor? I'm pretty sure your 94 requires electrical.
All the TH400s I've ever seen were purely mechanical with a single wire for the reverse lamps. Did they have versions with more wiring?

VSS with no speedo pass-through:

VSS with speedo pass-through:

Supposedly the early Astro vans have a pass-through VSS mounted near the dash, but I can't find any more info on a short search.
 

stutaeng

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All the TH400s I've ever seen were purely mechanical with a single wire for the reverse lamps. Did they have versions with more wiring?

VSS with no speedo pass-through:

VSS with speedo pass-through:

Supposedly the early Astro vans have a pass-through VSS mounted near the dash, but I can't find any more info on a short search.
I believe I've seen videos on TH400 and they've mentioned that it did have an electronic VSS, but it was only the last few years of production.

Here on post #13 they seem to say the same thing: https://www.performancetrucks.net/f...make-you-speedometer-work-th400-473927/page2/

Also mentions the strange 1500/4.3/TH400 combination...

I don't know if any of those parts are still available though. Maybe only on the aftermarket side?
 

PlayingWithTBI

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FWIU all you have to do is drop the tail shaft housing, pull the speedometer gear, install the VSS reluctor gear, and install the VSS sensor, and plug in the connector. Here's a thread with part numbers, YMMV

 

94chevc1500

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Update: I have installed the transmission I used my original driveshaft I did get a conversion u joint and got the drive shaft extended 2 inches that's all that was needed on that end. The crossmember bolts 3 out of 4 go in one is almost lined up perfectly just gotta try and maybe drill a little. The vss plug from the 4L60e plugged into the tailshaft on the th400. Does it work? I will find out as soon as I go down the road. The tbi still works just fine so far. I have not driven the truck so I don't know if it will do something weird if it goes into gear
 
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