samurai vibration

[WoodburyZuk]

So my neighbor has an 86. Sprung under on about 4” YJ with a sky kit with missing link. 31s and 6.5s in the case. Stock everything on motor. Stock carb.

Vehicle:
86' Samurai Stock Motor, Stock Carb
Sky YJ SPUA 31s
6.5 T.C w/ snatch

Issue:
Starts and Idles fine no issues at slow speeds

Under acceleration or on gas between ~20 & ~40 mph shakes very hard and has poor acceleration. If you let off the gas, or are going downhill at this speed the shaking instantly stops.

If you keep accelerating past 40 is smooths out again and cruising at 55 is fine.

We pulled the rear DS and it still happens. Haven’t pulled the front shaft yet… maybe front output shaft.

What yous think irates?

 

[YotaAtieToo]

Don't forget there is a shaft between the trans and tcase.

My guess would be engine, trans or tcase mount causing something to move under torque. Do either of the shifters move under acceleration?

 

[Gwagensteve]

Most likely a jackshaft uni on the way out or, as Yota points out, a bent/broken trans or transfer mount taking the jackshaft out of phase, which will take out a uni soon enough.

 

[skyhiranger]

So my neighbor has an 86. Sprung under on about 4” YJ with a sky kit with missing link. 31s and 6.5s in the case. Stock everything on motor. Stock carb.

Vehicle:
86' Samurai Stock Motor, Stock Carb
Sky YJ SPUA 31s
6.5 T.C w/ snatch

Issue:
Starts and Idles fine no issues at slow speeds

Under acceleration or on gas between ~20 & ~40 mph shakes very hard and has poor acceleration. If you let off the gas, or are going downhill at this speed the shaking instantly stops.

If you keep accelerating past 40 is smooths out again and cruising at 55 is fine.

We pulled the rear DS and it still happens. Haven’t pulled the front shaft yet… maybe front output shaft.

What yous think irates?

Does it only do it in 4wd and/or with the hubs locked? If not, then it isn't the front shaft, because it would not even be turning in 2wd with the hubs unlocked.
Sounds like it has something to do with something being under torque, since it doesn't do it when coasting or going downhill. So I would guess either a shaft issue or mount issue.