1994 Chevy G20 Van - Van (auto trans) only has high (D) gear

Donald, You did not state the model, so I posted the link for the models I found for chevy van fuse box. Check the attached links,instruction and guides, Good luck
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700R4 or 4L60 trans. Both the same. Time for a rebuild. The longer you drive it the more it will cost.

google fuse block diagram for a 1994 chevy g20 van, should pop right up

Check your E-break first, secondly check to make sure you have no errors kicking from the control unit (engine computer module) which may or may not trigger a check engine light. Moreover it could be several things. Since it's an automatic the drive train maybe damaged, controller unite could be damaged, the transmission could (and probably) is dying. I'd have a professional mechanic check it out.

I believe the seats are bolted to the floor of the van. Make sure you unplug all electrical connections before removing the seats.

sheering box nut shaft will be 120 ft/lb tie rod joints are 30-40ft/lb

change the transmission fluid & filter & add an additive like moly slip or stp for smoother changes

Okay, there are a few engines that come in this van, lucky there the same except,they come with or without ac or airpump, so i will give you all of them and you choose the right one.

1994 chevy 3/4 ton van, you have a 4L60E ?
You have to pull the trany pan, ther are 2 solenoids A and B. You will probably want to replace both, they are at the front on the valve block. www.rockauto.com

3 and 4 clutch pac . get it rebuilt