Hey. I have a 90 W150 that previous owned had started a EFI delete. And had done a real hack job. So what I have done is removed the elec. Fuel pump, added a mechanical pump. Which required the adding of the centric onto the cam gear. My current issues is I don't have speedometer, RWAL A/C and transmission shift/OD plus lock up. I do have a complete wiring harness from a 1986 D150 same engine. I was thinking it would same me time and money to swap engine and in cab harnesses. Then I could use the cable speedo. Go to a fire wall mount voltage reg. I would still retain the RWAL. The only mode needed would be for the trans overdrive and possible lock up. Any pro's and con's? Thank you K

 

Would you consider going back to TBI??? Might be less work. Not sure about cheaper or easier work.....

 

don't worry about the RWAL. i would personally remove anything relate to the system since it is more likely to leave you stranded with poor brakes. as far as the speedo goes all you have to do is figure out what is not working. it is a extremely simple system. there is pretty much 3 things to it. the speedometer itself, the speed sensor and wiring. just have to figure out which one is the issue. i usually use a electronic ignitions distributor hooked to a drill to test the speedometer. ground 1 wire and hook the other to the wire that goes to the speedometer. since you also have no od it could also be related to the speed sensor not working or wiring

 

I don't have a complete TBI system to work with. The truck had a carb on it when I bought it. I just replaced the complete dash, so taking it back out wouldn't be that big of a job. And changing the engine harness isn't to hateful. I'm just trying to save chasing all the gremlins with the TBI harness and PCM issues. My 1990 speedo also needs the odometer gear replaced. But the speedo is not working also. I have my 8 volt signal at the cluster pin. A crazy side not, I have been watching all the salvage yards. And not one 1st gen in any of them. 6 months ago they where everywhere in a 150 mile range. Florida doesn't have older vehicle anymore.

 

Thank you crazzywolfie. Yes I have done the diagnostic test on the speedo. I found the odometer has a crumbled gear, I have order a new one. The speedo has the correct input voltage that varies give speed sensor input. Fortunately I have a big box of OEM parts from my years of working at the dealership. It has a brand new speed sensor. I kept lots of spares. So I feel confident the motor that runs the speedo is inop. I will add I have the FSM, diagnostic manuals and parts catalogs. Which help but still a bit vague. No problem going without the RWAL. I could always go with a overdrive switch and pressure switch added to the A999. If that works? Never done the mod, looks simply. Would lock up need to be put on a toggle switch?

 

does you truck have a A999? if so then that is usually not a overdrive transmission. these are usually a 3 speed auto. easiest way to check if it is a overdrive transmission is crawl under it and see if it is overdrive or not since OD was very new and still not common in 90 and there is a good likelyhood since yours is 4x4 it doesn't have it. do you know what gear ratios are in the axles? if 3.23 it would likely be a non overdrive truck since trucks with overdrive usually came with 3.55 gears.

there could be something else wrong with the speedo. i have seen some where the motor in them would work on and off even after replacing the broken gear.

 

Here is my trans # PK45051540332 9520 . There is a 2 wire plug toward the rear of the trans housing where the OD switch is to be located. I need to back up a bit. When I bought this truck 5 years ago. The seller gave me a box with parts from Superior Transmission. Kit contains two pressure switches and a adjustable vacuum switch. He told me I needed these to correct the inop OD issue. The truck drove and shifted through the 3 gears fine. Its a clean rust free truck. So things happen and the truck has sat in the corner .
I have also installed a firewall voltage regulator, and old style electronic ignition. So no issues there. The truck had already had the EFI removed by previous owner.
If I can get this speedo working and make sure its shifting correctly in OD and Lockup. I would be good to go.
I will dig into the gear ratio, when I can get it on the lift. The truck still has the stock 15 inch wheels and 235's on it. Thanks

 

the transmission numbers mean nothing to me. the overdrive plug should be 3 wire or at least a 3 pin connector even if only 2 wires are used. the 2 wire plug is usually for the speed sensor. the od connector is usually within a couple inches of the neutral safety switch.

 

I know what what the speed sensor looks like. Yes its a two pin sensor, attaches on the transfer case where a speedo cable would if it used one. The 2 pin connector is in the main case of the trans toward the rear. The 1990 FSM shows it as a OD switch connection. The PK code is the factory number stamped on the trans case drivers side(left) just above the trans oil pan gasket . I need to find the RPO code book I once had, packed away somewhere. Again thanks for input.

 

I would suspect the speed sensor wires to go back the the pcm. It needs it for the trans and cruise if so equipped. Od and lockup trans will have a 3 wire plug. IF it has OD there would be a switch and indicator light in the drivers compartment.