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UFOtestpilot 12-22-2012 10:18 AM

Automatic Transmission Fluid Change Question
1999 Wrangler, 4.0, AT.

I'm going to change out the filter and the fluid, and I'm used to maintaining a different breed of vehicle so don't think I'm nuts, I'm checking my thinking here.

My question is whether or not running the old fluid out of the torque converter by disconnecting the return line at the radiator and running until new fluid shows is a seriously recommended step or just an overly anal thing to do? I'm usually overly anal with my vehicle maintenance but to be honest, I'm not really feeling this one since I don't have a lift handy. I can accomplish it nonetheless if it is highly recommended though.

jherrington 12-22-2012 10:22 AM

So I've heard, drop the pan change the filter change the fluid that was in the pan. Done. Flushing can do more harm than good. Especially on older vehicles that haven't had their transmissions regularly flushed.

Jerry Bransford 12-22-2012 10:30 AM

It's my strongest possible opinion that if doing a thorough flush to an automatic transmission as you described UFOtestpilot in any way causes problems, then the transmission was on its last legs anyway. What you described is how I would do it. The transmission needs to be in Neutral to do this, the pump doesn't run when the transmission is in Park. Be sure to use ATF+4.

UFOtestpilot 12-22-2012 10:36 AM

I don't mean using a flush, I just meant running the fluid through to prevent the old fluid in the TQ converter from contaminating the new.

UFOtestpilot 12-22-2012 10:38 AM

Aha, thanks Jerry! So it'll pump it in neutral? I thought it might have to be in drive. Nice!

jherrington 12-22-2012 10:47 AM


Originally Posted by UFOtestpilot
I don't mean using a flush, I just meant running the fluid through to prevent the old fluid in the TQ converter from contaminating the new.

Ah! I misread. My mistake.

UFOtestpilot 12-22-2012 10:56 AM


Originally Posted by jherrington

Ah! I misread. My mistake.

It's all good! I'm just happy I don't have to set up a redneck lift in my driveway to get the fluid out of the TQ converter! lol

UFOtestpilot 12-22-2012 11:15 AM

Ok, so how many quarts to run before I'll get the old fluid out? It's an all stock system.

Jerry Bransford 12-22-2012 11:19 AM

8-10 quarts will do it. Technically it holds 8 quarts but a little extra flush won't hurt.

32RH and 30RH (97-02 3 spd auto)

To avoid overfilling transmission after a fluid
change or overhaul, perform the following procedure:

(1) Remove dipstick and insert clean funnel in
transmission fill tube.
(2) Add following initial quantity of Mopart ATF
Plus 4 to transmission:
(a) If only fluid and filter were changed, add 3
pints (1-1/2 quarts) of ATF Plus 4 to transmission.
(b) If transmission was completely overhauled,
torque converter was replaced or drained, and
cooler was flushed, add 12 pints (6 quarts) of ATF
Plus 4 to transmission.
(3) Apply parking brakes.
(4) Start and run engine at normal curb idle
(5) Apply service brakes, shift transmission
through all gear ranges then back to NEUTRAL, set
parking brake, and leave engine running at curb idle
(6) Remove funnel, insert dipstick and check fluid
level. If level is low, add fluid to bring level to
MIN mark on dipstick. Check to see if the oil level
is equal on both sides of the dipstick. If one side is
noticably higher than the other, the dipstick has
picked up some oil from the dipstick tube. Allow the
oil to drain down the dipstick tube and re-check.
(7) Drive vehicle until transmission fluid is at normal
operating temperature.
(8) With the engine running at curb idle speed, the
gear selector in NEUTRAL, and the parking brake
applied, check the transmission fluid level.
CAUTION: Do not overfill transmission, fluid foaming
and shifting problems can result.
(9) Add fluid to bring level up to MAX arrow
When fluid level is correct, shut engine off, release
park brake, remove funnel, and install dipstick in fill

UFOtestpilot 12-22-2012 11:25 AM

Thank you kindly for the information!

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