I am working through a build and wanted to get some advice before I make any final desicions on the best route to take for my truck project. I have a 1995 V6 5spd truck that was bought without engine/trans but has complete engine/trans harness and the ECU. I have a 3vze out of a 1994 which would be a complete bolt in but the motor has a broken fan pulley bracket and is missing the timing cover (internal condition also unknown as the timing belt was installed incorrectly so I cant compresson test). My other option is a nice 3vze out of a 1990 that has a complete engine/trans harness and ECU. The engine compression has been confirmed good (150-170psi across the board).

My plan is to install the older engine (1990) but I have afew questions about the compatibility and what would ultimately be the easiet route

1. Should I install the 1990 engine with its original harness and ecu as a direct bolt in...possible issues with older ecu compatibilty with the newer truck? missing electric speedo harness
2. Should I install the 1990 engine with its original harness but use the ecu from the 1995...possible issues with newer ecu compatibility with older motor? still would be missing the speedo harness
3. Should I install the 1990 engine using the harness and ecu from the 1995 engine...possible issues with distributor/wiring, knock sensor wiring? Speedo issue would be solved

I do have the "mostly" complete 1994 engine which could be used as a parts donor but I would like to eventually fix as a spare engine so would prefer to avoid stealing parts if possible. I am fairly new to the world of toyota but have been reading as much as I can about what does and doesn't work. Just hoping to get some wisdom from anyone who has been there before. Thank you

 

Nothing?? I must have read 4 or 5 different threads asking to same question but none seemed to have a definite answer about ecu's and harness compatibilty. After exploring the forum more I realize I probably should have posted this in the engine swap forum...even though its a 3.0 to a 3.0...If it would be better over there please move my post. Thanks

 

The only issue I can think of that you might have trouble with is that speedo. I'm not too savvy on how to solve that, otherwise I don't think Toyota changed much else within that generation of trucks. If your cluster has gauges you'll need the corresponding sending units (water temp, oil pressure, etc.). If it has dummy lights then you will have temp and oil switches instead. Make sure you don't use a switch style unit with a gauge. Otherwise, as long as the ECU matches your truck (4x4 or 4x2, auto or manual trans, correct engine) you should be good to go.

 

Thanks for the response. I do have the speedo harness which could be ran and pinned into the ecu harness but im not sure if the 1990 ecu had that capability already or they added that circuit for the later years? I would prefer to swap the 1990 engine complete with matching ecu and harness is possible....Im pretty sure the clusters on the 1990 and 1995 truck both had gauges but I need to confirm that when I get back to the shop. Either way I really appreciate the input. Thanks again

 

The 1995 is probably an electronic speedometer and the 1991 is a mechanical one. Since the 1991 drive train is going into the vehicle, the simplest course would be to go with the 1991 speedometer drive cable and the mechanical speedometer. The speedometer assembly is a self contained unit, so you might be able to use the 1995 gauge cluster with the 1991 speedometer assembly. You can make sure the cable is good by holding one end of the inner piece in your fingers and trying to turn the other end. If its spongy feeling, its worn out and the needle will wobble. New ones are still available from your favorite online Toyota parts source.

 

I had thought about converting it to the mechanical speedo. The issue is that the 1990 transmission was reported to be "grinding" alitle so I was going to use the transmission from the 1994 which has no issues. The other problem is the cluster from the 1990 is not in good shape and the speedo cable itself is also pretty rough. I didn't know you could swap out just the speedo unit itself which would make it possible to keep the 1995 cluster and just use the older speedo. Also I suppose I could pull the mechanical speedo mechanism out of the older tranny and put it in the 1994.....If the older ECU has no provision for the electronic speedo then it might be the best option. Thanks for the idea

 

Sorry about the late response.
I know NOTHING about the 4 runners and trucks after 1989... never even seen a 3vze except in pics on the forum.
sounds like your having fun and good luck with your project.

 

Ok, can you post a picture of the speedo connection on the 1994 donor tranny? It’s probably electronic which would work with the 95 cluster.

 

Another thought. On the 1991 mechanical speedo, it’s just a cable between the tranny and the speedometer head unit - no ECU connection. I bet the electronic one replaces the cable with a a wire from the tranny to the head unit and the ecu is still not part of the loop.

 

From what I can tell the speedo is driven from an ecu signal (pin#9 spd) I can see the output signal from the ecu to the combination meter in the wiring diagram but I cannot seem to find the input to the ecu from the VSS in the schematic. I think that I am going to swap the newer harness onto to old motor and use the ecu from the 1995. Im also going to swap over the new style distributor and alternator from the 1994 motor so everything is plug and play. I will likely have to swap some sensors/switches too but it all depends on what cluster the older truck had. Im back at the shop tomorrow so i'll be able to sort some stuff out.

 

If I were you I'd go that route as well. Sounds to me like the best option. Good luck!