Cluster swap tach question

[OldSch88L]

I just completed my cluster swap from stock dummy lights cluster on my 1988 renix 2.5, to a full gauge cluster from a '95 or '96 Cherokee.  XJs are getting pretty rare where I live so the full electronic cluster is pretty much the only deluxe cluster I could find at the junkyard. I cross-referenced wiring diagrams for both and swaped in the '96 connector, converted to VSS speedo by making and wiring my own harness, and swaped the oil pressure and water temp sensors. Everything works fine except gas gauge works backwards, which was expected. Every post I read about cluster swaps say that the 4.0 tach should read slower in my case at 2/3rds. Thing is, it seems somewhat accurate, idle being around 1000 rpm, and the rest of the time it seems to match the engine"s speed pretty well by ear... I checked and the tach in that particular cluster didn't have any adjustment screw on it. And I'm pretty sure it came from a 4.0 Cherokee because it was a pretty well equiped model. Anybody has a theory?

[eaglescout526]

Maybe an H.O. member might be able to tell you but the Renix clusters do have an adjustable tach. Have you taken apart the cluster to get to the back of the tach to find the potentiometer? 

[Ωhm]

56 minutes ago, OldSch88L said:

Every post I read about cluster swaps say that the 4.0 tach should read slower in my case at 2/3rds.

Wouldn't that be 1/3rd slower.

[OldSch88L]

1 hour ago, eaglescout526 said:

Maybe an H.O. member might be able to tell you but the Renix clusters do have an adjustable tach. Have you taken apart the cluster to get to the back of the tach to find the potentiometer? 

Yes I did take the deluxe ('96) cluster appart to adjust it, but like I said, the tach had no adjustment screw whatsoever :S

[OldSch88L]

40 minutes ago, Ωhm said:

Wouldn't that be 1/3rd slower.

Yes exactly; the 4 cylinder tach signal is 2/3rd that of the 6 cylinder, so it is 1/3 slower, or at least should be... But weirdly, it seems pretty accurate in my case!

[mnkyboy]

When my 89 had the Renix system I had to adjust the tach, when I converted the truck over to the Chrysler MPFI system I used a 4.0l HO cluster and it was just plug and play.

[Eagle]

On 3/17/2020 at 9:34 PM, eaglescout526 said:

Maybe an H.O. member might be able to tell you but the Renix clusters do have an adjustable tach. Have you taken apart the cluster to get to the back of the tach to find the potentiometer? 

 

Not all the Renix tachs were adjustable. Don't forget, the '86 2.5L is a Renix. The adjustable tachs are the ones in the "Type 2" clusters. The Type 1 clusters did not have the potentiometer.

[OldSch88L]

On 3/19/2020 at 3:11 AM, Eagle said:

 

Not all the Renix tachs were adjustable. Don't forget, the '86 2.5L is a Renix. The adjustable tachs are the ones in the "Type 2" clusters. The Type 1 clusters did not have the potentiometer.

Not familiar with type 1 or 2,  but the date on the full, replacement cluster was from the nineties, 1996 IIRC.

[Eagle]

5 hours ago, OldSch88L said:

Not familiar with type 1 or 2,  but the date on the full, replacement cluster was from the nineties, 1996 IIRC.

 

Type 1 and Type 2 refer to clusters with mechanical speedometers. 1996 is electronic -- it's neither Type 1 not Type 2.