Instrument cluster shows 4x to 5x the actual speed

Joined
Oct 23, 2018
Messages
24
Location
Iceland
I've been working on a diesel transplant in my 1992 80 series truck, where an old 1HD-T replaced an 1FZ-FE with broken head gasket. The diesel transplant called out a different wire harness which required a different instrument cluster, which has a cable directly from the transfer case into the back of the cluster (not electric signal). During the first test run with the cluster installed, the speedometer showed something like 4x to 5x the actual speed of the truck. Does anyone have an idea about what could be happening?

The truck is on 39x14.5R15 IROK tires and the old speedometer was very accurate on those tires. I was quite surprised seeing this behavior.

A pic of my truck...
20190906_200937.jpg
 
Joined
Jun 3, 2006
Messages
294
Location
Panama city, Rep of Panama
I find strange that of the wiring, I would have kept the old TC and run the electrical signal to the cluster...by cable it means that it is the very old model, like the ones that came with A440F back in the day...mine has a 1HD-T with an electrical sending unit to the cluster...if you want to keep the TC just place an electrical sending unit in there and reuse your old wiring...diesel need basically one positive to the engine to run, the rest is for the car itself...maybe 3 cables if you wish...two for the IP to RPM meter and 1 to the fuel cut solenoid right in there...I NEVER use the glowplugs as it is direct injection and over here it never gets that cold
 
Joined
Oct 23, 2018
Messages
24
Location
Iceland
The transmission installed is the older (first?) generation of A442F, with hydraulic controls only (not the A440F though). I followed an advise to replace the electrical system too which has now been done, and the truck runs and drives with some few electrical hiccups. It is counting the kilometers correctly which I believe indicates a correct signal being transmitted to the cluster, and the cluster being screwed up.


I find strange that of the wiring, I would have kept the old TC and run the electrical signal to the cluster...by cable it means that it is the very old model, like the ones that came with A440F back in the day...mine has a 1HD-T with an electrical sending unit to the cluster...if you want to keep the TC just place an electrical sending unit in there and reuse your old wiring...diesel need basically one positive to the engine to run, the rest is for the car itself...maybe 3 cables if you wish...two for the IP to RPM meter and 1 to the fuel cut solenoid right in there...I NEVER use the glowplugs as it is direct injection and over here it never gets that cold
 
Joined
Jun 3, 2006
Messages
294
Location
Panama city, Rep of Panama
There are two A442F variants...the first models (I am only talking about diesel engines mostly) are the ones that came with the old dash, meaning an ECT button, the newer dash has PWR and 2nd Start...basically, the sole thing you change is the Neutral Safety switch as the old one is round and the new one is squared...the second variant of the A442F is also known as the AW450-43LE and came in 100 series diesels up to 2002 with the 1HD-FT engine...inside one has the teeth squared (new) and the other like triangles...just in case you get to open it, the older one is easier to fix (just did mine in about 1 day)...besides the transmission, the transfer case (TC) is what changes, mine has the one with free wheel locking hubs meaning it has the HV1A (or something like that) the older model has the same TC, the sole thing that changes is the sending unit, one is cable and the newer is electrical...I will understand that you change the electrical wiring if you started with a car that had an A343F, otherwise, it make no sense to me...and that is if the computer actually changes, otherwise you only needed the part that goes to the transmission...easy does it...
 

Users who are viewing this thread

Top Bottom