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Old April 21st, 2019, 18:43
soyjer soyjer is offline
NAXJA Forum User
Join Date: Aug 2017
Location: California
Posts: 145
Re: Please try this with your XJ and tell me results?

Originally Posted by ShoeterMcgav View Post
I thought I explained the why it does from N and not R... Load.

When in R it is under load and so the switch tp D keeps it under load. N takes the load off the trans and driveline. R to D keeps the rotaional masses under load, just changes the direction- so it only changes in the tranny aince you arent moving. When in N to D you are reapplying this force to the whole driveline.

Trans sounds fine- its new right??
If mounts are good there may be a backlash adjustment needed but sounds like probably not. With out pulling the axles and diff cover to check the carrier, bearings, and shims- you have to call it good.

800 is pricey for a stock axle... Maybe instead of a rebuild get a quote on new bearings- or axle seals and all that will be checked when in there
If you are saying that loose motor mounts could cause the clunk/lurch, I am liking that, because if they could, then, as you point out, this fits in nicely with the pausing in Neutral causing the clunk/lurch.

If so, I may need a physics lesson to fully understand how it works.

I've been sitting here trying to understand how this would work, and I THINK I have come up with an analogy that fits:

Picture a car where the huge, heavy engine block rotates around a stationary crankshaft bolted to the firewall, and the driveline is therefore driven by the rotating engine block instead of the crankshaft. If you revved that rotating engine block up to 1000 rpm and then popped the clutch, you couldn't possibly stall the engine, correct? The rear wheels would spin far before the engine block would stop rotating?
On the contrary, with a conventional setup, you only have to stop the relatively low mass of the internal moving engine parts to stall the engine?

Is the above why loose motor mounts would impart a heavier blow to the drivetrain than tight motor mounts?...because of the momentum of the heavy rotating engine block compared to the relatively low momentum of just the internal moving engine parts?
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