99 XJ: Auto tranny "thump" into gear from start

wolf2600 · Oct 7, 2013

I have a 99 XJ 4.0L auto with 125k miles.

I stop at a stop light, then when I start moving again, the transmission kind of "thumps" into gear right as I start rolling/accelerating. It's between 0-5mph when it happens.
No other problems with shifting.

Ideas as to the problem/fixes?

Thanks.

SanDiegoXJ · Oct 7, 2013

first guess would be a bad mount...could be tranny or engine...but I'd start by looking at the tranny mount.

Ronbo · Oct 7, 2013

Check the fluid level in the trans first.

wolf2600 · Oct 7, 2013

SanDiegoXJ said:
first guess would be a bad mount...could be tranny or engine...but I'd start by looking at the tranny mount.

It feels like the tranny actually shifting into a gear. Just that's it's shifting really roughly.

SanDiegoXJ · Oct 7, 2013

yeah, I had one friend who had a similar thing anytime he left a stop sign or stopped at one...it was like it was engaging and disengaging really rough....turned out to be a bad tranny mount and on engage and disengage the tranny would shift.

had another friend who had similar issues on acceleration, turned out to be the driver's side engine mount.

in both cases you can see if the rubber is trashed or still good...it's not like you have to remove anything.

Fluid level is another good option.

wolf2600 · Oct 7, 2013

SanDiegoXJ said:
yeah, I had one friend who had a similar thing anytime he left a stop sign or stopped at one...it was like it was engaging and disengaging really rough....turned out to be a bad tranny mount and on engage and disengage the tranny would shift.

had another friend who had similar issues on acceleration, turned out to be the driver's side engine mount.

in both cases you can see if the rubber is trashed or still good...it's not like you have to remove anything.

Fluid level is another good option.

Interesting. I'll check them out.

xcm · Oct 8, 2013

While your under the vehicle, check the driveshaft ujoints. Grab onto the driveshafts at the ujoints and give it a strong shake, it shouldnt move.

joe_peters · Oct 9, 2013

xcm said:
While your under the vehicle, check the driveshaft ujoints. Grab onto the driveshafts at the ujoints and give it a strong shake, it shouldnt move.

Agree.

Also, while under, look for "slop" at the rear differential.

Remember, with an auto trans, you are "in gear" unless you are in Park or Neutral.

MAY POP · Oct 10, 2013

The splines in the rear drive shaft are dry.
Set the parking break.
Remove the 4 small bolts from the rear driveshaft at the rear axle.
Remove driveshaft.
Lube inside of yoke and splines of yoke with Anti-seeze. The silver works real good.
Reassemble the shaft.
This will last for about 6 months and will need to be repeated when the clunk returns.
Ron

99 XJ: Auto tranny "thump" into gear from start

wolf2600

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SanDiegoXJ

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Ronbo

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wolf2600

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SanDiegoXJ

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wolf2600

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xcm

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joe_peters

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MAY POP

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