Guage Cluster Question

[Eagle]

So all I need is an 87-90 cluster...sweet! How do you adjust the potentiometer? Does it only have 2 positions or do you hook up an external tach and dial it in to match?

 

If the cluster is coming from a 4.0 and going into a 4.0, then there isnt any adjustments needed.

 

how about a 4.0 going into a 2.5?

A tach from a 4.0L going into a 2.5L will have to be adjusted. It will read wrong by a considerable margin.

 

All a tach does is count ignition pulses. On a 6-cylinder engine, one revolution is 3 pulses. On a 4-cylinder engine, one revolution is only 2 pulses. It takes the 4-cylinder 1-1/2 revolutions to generate 3 pulses, but the tach will only show 1, so if the tach says the engine is turning 1,000 RPM, it will actually be turning 1,500. If the tach says 3,000, the actual RPMs will be 4,500.

[jaekl]

So all I need is an 87-90 cluster...sweet! How do you adjust the potentiometer? Does it only have 2 positions or do you hook up an external tach and dial it in to match?

 

If the cluster is coming from a 4.0 and going into a 4.0, then there isnt any adjustments needed.

 

how about a 4.0 going into a 2.5?

A tach from a 4.0L going into a 2.5L will have to be adjusted. It will read wrong by a considerable margin.

 

All a tach does is count ignition pulses. On a 6-cylinder engine, one revolution is 3 pulses. On a 4-cylinder engine, one revolution is only 2 pulses. It takes the 4-cylinder 1-1/2 revolutions to generate 3 pulses, but the tach will only show 1, so if the tach says the engine is turning 1,000 RPM, it will actually be turning 1,500. If the tach says 3,000, the actual RPMs will be 4,500.

 

Lived that way for 18 years until I got a good deal on a 4cyl tach. No big deal just multiply the reading by 1.5. Selection in the junkyard wasn't so good in 1986-1987. I put a 1985 cluster in a 86 and to think the factory told the sales manager that adding gauges probably couldn't be done. Havn't bought a new car since.

[xj_dummy]

Can i use an automatic speedo wire on my 5 speed?

[Eagle]

Can i use an automatic speedo wire on my 5 speed?

On your 5-speed? Your signature says it's an '86. That should have a mechanical speedometer -- there isn't any wire.

[xj_dummy]

Can i use an automatic speedo wire on my 5 speed?

On your 5-speed? Your signature says it's an '86. That should have a mechanical speedometer -- there isn't any wire.

I'm sorry, need more info.

I have found a 89 xj limited at the local wrecking yard and I was wondering if the spedo cable out of IT, that has an auto, would work, so I can upgrade the spedo wire and gauge cluster to work on my 5 speed.

Because trying to find 84 to 86 xj is a lil difficult out here in non snow land.

mike

[Eagle]

So you're not asking about wires, you're asking about the speedometer cable?

 

Auto or 5-speed isn't the difference. There are two issues:

 

First, the 84 thru 86 (and possibly part of the 87 model year, I'm not certain) used a speedo cable with a metal end at the speedo head and a metal retaining clip that screws to the back of the cluster. The 88 thru 90 (and either all of 87 or possibly just the last half of the 87 model year) used a white nylon pinch connector to retain the cable on the speedo head.

 

Second, at least for the 87-1/2 thru 90 types, the speedo cable w/o cruise control is one piece, but with cruise control there is a short cable about a foot long off the speedo head, which then mates to a longer cable that runs to the transfer case and also feeds the cruise control data.

 

The short answer is that you can use an 88 - 90 speedo in your truck if you replace your speedo cable with one from the same year vehicle as the cluster. I think that's what you wanted to know.

[xj_dummy]

So maybe I should get the cluster from the wrecking yard and then go to autozone to get a non cruise cable for the spedo for that year cluster.

I thought it would be easier to get both at the same time.

Thanks for your help.

[Eagle]

If you don't have the cluster yet, yeah -- get the cable with the cluster and it should work.

 

Just take the core out of the "new" cable and lube it before you put it in your truck. And be sure to route it so you avoid sharp bends.

[xj_dummy]

So all I need is an 87-90 cluster...sweet! How do you adjust the potentiometer? Does it only have 2 positions or do you hook up an external tach and dial it in to match?

 

If the cluster is coming from a 4.0 and going into a 4.0, then there isnt any adjustments needed.

 

how about a 4.0 going into a 2.5?

A tach from a 4.0L going into a 2.5L will have to be adjusted. It will read wrong by a considerable margin.

 

All a tach does is count ignition pulses. On a 6-cylinder engine, one revolution is 3 pulses. On a 4-cylinder engine, one revolution is only 2 pulses. It takes the 4-cylinder 1-1/2 revolutions to generate 3 pulses, but the tach will only show 1, so if the tach says the engine is turning 1,000 RPM, it will actually be turning 1,500. If the tach says 3,000, the actual RPMs will be 4,500.

So how do you adjust the tach from a 6cyl to a 4?