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Hello all, I have an 84 coupe with a 4+3 that has the rocker switch for engagement, that has a bad OD unit. When looking for a replacement do I have to look for an 84 unit or will any year work as a replacement....? Thanks !
To the best of my knowledge, their pretty much interchangeable.
With the exception of the switch on the trans side cover plate that controls the OD and prevents use in Ist gear. Here's a partial schematic. Let me know if you need the side cover safety switch diagram, I'll need to did into my '87 C4 build book.
Before you remove your trans, be sure to complete the trouble shooting tests. Many times it's not the OD unit, but,,, a relay, , OD switch, OD trans fluid pressure switch, wiring, connectors, or a switch side of the the trans
The 86 and up received all the updates to make it more reliable. Chances are any of the 84-86 od units have been rebuilt to the 86 updates by now though. The throttle cable can be left disconnected. The 84, according to SK speed is a little special compared to an 85 or 86. I think its just the od ratio though. Later cars had a different ratio for the z51 vs base. Could be wrong though. That was one thing mentioned to me by them though. If just pulling a junk yard unit, go for the 86 up though. Chances are its fine.
As far as interchange... they all do. The 84 has a different pump so it makes more noise.
Later cars had a different ratio for the z51 vs base.
In addition to the Z51 tag on the car you'll see MH2 (non-Z51) or MK2 (Z51) for the OD ratio. I can't remember them both off the top of my head, but I think MK2 was a 0.88 reduction and MH2 may have been around 0.85. They were pretty close to each other.
In addition to the Z51 tag on the car you'll see MH2 (non-Z51) or MK2 (Z51) for the OD ratio. I can't remember them both off the top of my head, but I think MK2 was a 0.88 reduction and MH2 may have been around 0.85. They were pretty close to each other.
4+3 swap out question
