rb26 vibrates at higher RPM

[Frankyy]

so to start off, my car is a 1990 Nissan 240sx with a 1997 rb26dett installed in it

it has mckinney mounts, mckinney driveshafts and an RB25 transmission

when the motor was out of the car last winter during my swap I got the rb20 flywheel machined, I then installed an ACT clutch and I also replaced the OEM belt for a greddy belt along with OEM idler and tensionner.

If I am above 6500 RPM for more then 5 seconds the whole front end starts to vibrate, like a minor shaking, in 3rd gear at 6500-7000 RPM it will do it but it won't do it at 4k RPM in 5th gear so the problem is RPM based and not speed based, I eliminated the fact that it could be unbalanced wheels or driveshaft but rather flywheel? harmonic balancer? clutch? crank? timing is off a little? it's nothing big but it's big enough to make me post this thread after searching the web for an hour on other people's similar issues althought nobody seems to have this happen to them

Keep in mind the car is parked for the winter and I am just trying to shuffle ideas around for when it does come out I have a sense in wich direction to start looking

what I have done since and nothing has improved:

I have gone for a second alignement, changed axles and changed diff but the problem is still there


Has anybody heard of this problem before or experienced it themselves? I am now saving up for a house so I would rather not just go out and buy all new stuff and try it on till it goes away.

Thanks in advance!!

[Skym]

when the motor was out of the car last winter during my swap I got the rb20 flywheel machined, I then installed an ACT clutch and I also replaced the OEM belt for a greddy belt along with OEM idler and tensionner.

If OEM damper has no chips it should be ok. Take OEM damper off and check balance (same with flywheel). If one of those two are out of balance, could have done some internal damage.

In some cases the clutch can be too strong or have a solid centre disc that can damage engine, transmission. On some engines the too strong clutch can damage thrust bearing and make crank walk which as far as I know causes what you are describing.

[Frankyy]

hmm, I installed the 6 puck sprung clutch, the first drive I did with the car with the new motor in april I noticed it, a friend of mine has been running the same clutch in his rb25 for 3 years and doesn't have this issue, I didn't think I was gonna be looking into swapping clutches over.

should I just start off by taking flywheel off, clutch off and getting them checked for balancing?

anything else I should check?

[bourquetc]

check your engine mounts may be cracked or loose

[speedfreak]

Start by pulling the balancer off and getting it checked.

[Frankyy]

ok I will do that, and I had in mind of installing an ATI balancer when the motor was out and didn't go threw with it that may be in the near future

[Voodoo_ChildR32]

RB flywheels are non serviceable. It is stated in the FSM and is usually not advised with a hydraulic clutch setup. Try a new flywheel and see if the problem continues.


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[speedfreak]

Balancers are two pieces of steel.

An outer ring and an inner hub. Sometimes the rubber separates between the two and the outer ring will slip or twist causing a balance problem.
As far as I know there are two companies making balancers for rb
One is ATI the other is Ross performance.
Ross carries three options and also have some things like trigger wheel and dry sump drive options to consider for the future.
Take a look at the balancer and see if you can see signs that the rubber had separated. I'd use my phone to take video or pictures cause its a tight spot.

Also just want to ask if you are confident it is not an ignition coil crapping out and shaking the engine.

[Frankyy]

The balancer was removed with a steering wheel puller with absolutely no effort( i was turning the 19mm bolt woth my hands to pull it off) after the 2 harmonic balancer puller bolts holes stripped on me, it is not bent in any way but had a hairline crack in the rubber part of the balancer,

I'm aiming more towards balancer or clutch assembly, I'm gonna look into getting them check for balancing

[Frankyy]

Sorry, double posted

[speedfreak]

If you were removing the balancer by turning the puller bolt by hand and very easily I would be concerned that the balancer to crank clearance is too loose.
I measured my crank nose at 30.02mm and the inside diameter of the balancer at 29.98mm
check it against yours.

[speedfreak]

I tried to measure the keyway from the back to the yellow timing mark to give you a referance to check and see if it has spun.

[Frankyy]

It's a tight fit the clearance is good, when the puller holes stripped it probably loosened it for the first time, I've pulled the balancer off twice afterwards and feels just like a balancer should feel, I was using the expression of loosely turning by hands in reference that I didn't torque anything against the outside pulleys

When I get the chance tho I will go to my car and check it out, it's in storage at the moment and I need to bring all my own tools to it, gotta love winter!

[Frankyy]

Thanks a lot! It will give me a good reference point!