Difference between Renix flywheel and H.O. flywheel?

[johnj92131]

While looking on Ebay for a clutch kit to use with the AX-15 on my TDI conversion I noticed listings for 4.0 flywheels were different for the Renix era from the H.O. era.  I had been looking at LUK clutch kits specifically when I noticed that different flywheels also seemed to be specified. 

 

Is there a difference in the 4.0 flywheel from 1990 to 1991?  I know the transmission spline count is different (21 vs 23), but why would the flywheel be different?

 

Thanks for any pointers.

[Hippie66]

Following

[Hippie66]

O'Reilly Auto Parts shows different clutch for '89-'90 than for '91- '92.

[DirtyComanche]

They're different because the ECM reads the output from the crank position sensor (CPS) differently Renix vs HO.  I don't know if there is other differences or not.

[87MJTIM]

Is there a difference in the 4.0 flywheel from 1990 to 1991?  I know the transmission spline count is different (21 vs 23), but why would the flywheel be different?

 

Thanks for any pointers.

 

 

The 90 was Renix; the 91 was HO.  They use different fuel systems/electronics.  The flywheels are different.  The Jeep's CPS count the teeth on the flywheel to tell the computer where the crank is and which injector to fire.  I don't know how the TDI's electronics work with the flywheel.  It seems to me you would want electronic to that engine.

 

As for spline counts, that is at the other end of the trans, where it bolts to the tcase.  In 90 and 91, each yr. came with the AX15 with 23 splines-out.  That should not be an issue for the TDI.

[johnj92131]

Thanks to both of you.  The CPS certainly makes sense.  The TDI gets its crank position information from the front of the engine once the flywheel is at top dead center, the injection pump is mechanically timed and locked down. 

 

My kit comes with a 4.0 starter, I need to supply the clutch and flywheel for the AX-15.  My next issue is if I want to convert from the internal slave to the external slave now or just keep the internal slave.

 

Has anyone converted to the external slave without changing the bell housing?

 

 

They're different because the ECM reads the output from the crank position sensor (CPS) differently Renix vs HO.  I don't know if there is other differences or not.

 

 

 

Is there a difference in the 4.0 flywheel from 1990 to 1991?  I know the transmission spline count is different (21 vs 23), but why would the flywheel be different?

 

Thanks for any pointers.

 

 

The 90 was Renix; the 91 was HO.  They use different fuel systems/electronics.  The flywheels are different.  The Jeep's CPS count the teeth on the flywheel to tell the computer where the crank is and which injector to fire.  I don't know how the TDI's electronics work with the flywheel.  It seems to me you would want electronic to that engine.

 

As for spline counts, that is at the other end of the trans, where it bolts to the tcase.  In 90 and 91, each yr. came with the AX15 with 23 splines-out.  That should not be an issue for the TDI.

 

[87MJTIM]

 

Thanks to both of you.  The CPS certainly makes sense.  The TDI gets its crank position information from the front of the engine once the flywheel is at top dead center, the injection pump is mechanically timed and locked down. 

 

My kit comes with a 4.0 starter, I need to supply the clutch and flywheel for the AX-15.  My next issue is if I want to convert from the internal slave to the external slave now or just keep the internal slave.

 

Has anyone converted to the external slave without changing the bell housing?

 

 

 

In a word: No.

 

You will need the bellhousing, the internal shift/release bearing fork, and the front bearing retainer cover.

 

The bearing retainer cover for the internal is a short sleeve.  The external cover has a long sleeve (to account for the release fork movement.)

[desbennett004]

So, I will be putting my AX15 from my 99 cherokee into my 89 Comanche. The way I understand it is I will need an 89 flywheel, but a clutch kit for a 99 AX15? I have also been told there is a different sized bushing needed? Anyone have a size/ and/or part number for that?

 

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[87MJTIM]

You are correct: 89 flywheel and 99 clutch kit.  Additionally, you will need a hydraulic kit (master/slave cylinders). Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=1136086&cc=1180213&jsn=1 Don't get the later kit.  The master cyl will interfere with the brake booster and the bolts are wider then the original bolt holes.

 

I got a pilot bushing for a 75 CJ5, 304 V8.  Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=628303&cc=1309441&jsn=3

[johnj92131]

Good information!  And not unexpected.  Thanks.

[desbennett004]

You are correct: 89 flywheel and 99 clutch kit. Additionally, you will need a hydraulic kit (master/slave cylinders). Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=1136086&cc=1180213&jsn=1 Don't get the later kit. The master cyl will interfere with the brake booster and the bolts are wider then the original bolt holes.

 

I got a pilot bushing for a 75 CJ5, 304 V8. Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=628303&cc=1309441&jsn=3

Good info, thanks.

 

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[desbennett004]

You are correct: 89 flywheel and 99 clutch kit. Additionally, you will need a hydraulic kit (master/slave cylinders). Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=1136086&cc=1180213&jsn=1 Don't get the later kit. The master cyl will interfere with the brake booster and the bolts are wider then the original bolt holes.

 

I got a pilot bushing for a 75 CJ5, 304 V8. Rockauto - https://www.rockauto.com/en/moreinfo.php?pk=628303&cc=1309441&jsn=3

Good info, thanks.

 

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[mikekaz1]

CPS don't read tooth counts. They read "gate" values. Little squares punched into the flywheel flange. The size / tooth count on renix and HO 4.0 (2.5?) flywheels are the same as the starters are interchangeable.

[gogmorgo]

:yeahthat:

The Renix flywheel has a ton of windows around the edge, with three of them being slightly longer to trigger spark events. The HO only has three windows, each one triggering a spark event.

[1987Comanche]

 I compared the Renix to HO flywheels a few years ago.  The trigger windows are mirror images of each other.  Every positive "tooth" on the Renix flywheel is a "void" on the HO flywheel.  I used to have a pic of them side by side...have to see if I can dig it up.

[desbennett004]

I compared the Renix to HO flywheels a few years ago. The trigger windows are mirror images of each other. Every positive "tooth" on the Renix flywheel is a "void" on the HO flywheel. I used to have a pic of them side by side...have to see if I can dig it up.

Can you put the flywheel in incorrectly? It seems to me it can only go in one way, or the holes don't line up. Is that right? I have mine installed, it starts fine, but it won't go above idle without popping and missing. I'm thinking it's the CPS, but wanted to make sure I put the flywheel in right. If what you say is true, if they sent me a HO flywheel for my Renix, would it run badly like mine is doing, or would it not run at all?

 

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[Jackrabbit41]

I tried using a HO fly wheel in a 87 renix and it did not work. Cps doesn't work

[desbennett004]

I tried using a HO fly wheel in a 87 renix and it did not work. Cps doesn't work

Found the problem, looks like I broke the vacuum line to the MAP sensor!

 

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