Bucking and jerking on decel

[EHENLEY2]

I have a 81 CJ7 with 32 inch tires not sure what diff ratio is (yet) T-176 Transmission , 4.6 fuel injected stroker. (the original drivetrain was a AMC 258 i6 / 4.2l and SR4 Transmission )When I decelerate I get a bucking in the drivetrain. if I accelerate the bucking goes away, so as long as I have pressure on drivetrain its does not buck, ( new drive shafts and new u joints) My gut is I don't have enough gear but before I spend $ on new diff gears I thought I would ask the question of more experienced jeepers

 

[Torxhead]

A CJ with 32" and larger tires, should have some change in rear gear ratio. There are a few charts on the www that should help you out. I am thinking you might have the throttle position sensor out of adjustment or a ignition timing issue. If you have an exterior mounted fuel pump, it also can make problems for you. Like not having a properly vented fuel tank or clogged fuel pickup sock. With fuel injection, you should check the fuel pressure to the throttle body every now and then.

 

[Roadkil]

Check your driveline angle for proper operation, under load will smooth the angle out and without load more vibration.
Make sure your u-joints are parallel to one another to help cancell out this vibration. For example draw an imaginary straight line out of the Transmission output shaft and the same with the pinon gear, they make a tool for this. Those lines should be parallel.
Hope this helps
Roadkil

 

[Hedgehog]

Does the engine actually back fire under deceleration?

 

[Woolyworm]

Can you describe the bucking a bit more? Are you sure the engine is running on decel? Does it do it with the clutch in? At all speeds? I don't think this would have anything to do with your gear ratio.


Wooly