DJ5D (almost a CJ-5) power train rythmatic 1 second vibration at 1800rpm

[forjack842]

I could sure use a clue.
Ive got a 75 DJ%-D I232 and a a727/dana. Engine and tranny are an earlier version as the exhaust manafold is missing the EGR.

I've had the tranny just serviced by the best here in my area and everything looked fine. Just replaced the motor mounts and tranny mount with new. U joints are good.

The issue I have is a vibration that comes and goes at about 1 second at around 1800 - 2000 with or without in drive or in park. Rythm of vibration does increase/decrease with rpm but is most noticable at 1800-2300 rpm.

ideas??

Thanks

 

[mylittlecj5]

did they use the correct flexplate for the engine? kinds sounds like the engine isn't balanced just right. Maybe the harmonic balancer slipped? throw a timimg light on it, mark it, then static time it. see if there is a difference where the marks line up.

did you use rubber or poly mounts? the poly will transmit more vibes thru them. I'm betting you used rubber, tho.

 

[forjack842]

Rubber mounts. That actually reduced the vib alot but its still felt in the steering and the gear shift floor stick (auto)

Not sure on the flex plate. I'll drop the tranny inspection cover this weekend and check torque on the bolts. I'll have to check the TSM and see if there's any alignment marks on the tranny to flywheel interface to check for also.

I replaced the old delco point/cap distrib and coil with the stock prestolite orig equip (dist, elect module and coil) for the 75 series and checked the harmonic balancer vs the dist vs #1 cyl. All were right on when buttoned up.

The vib does feel like an imbalance as if rises in amplitude and decays at about a 1 second repeating rate at 1800. Increase the RPM to 2200 and its a faster repeating cycle but not as noticable. Lower the RPM its a longer duration between and less noticable also.

Definately feels like its in the engine/tranny since with it in neutral or park you still feel a decent vib as you increase rpm in the 1800 range.