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AW4 Delayed Reverse

wireman121

NAXJA Forum User
Location
NJ
I've been looking all over for some help with this. I read through the AW4 manual, but it leaves out much mention of the first/reverse brake which is where I suspect my problem is. Anytime I shift into reverse, there is about a 3 second delay until reverse engages. Once its engaged it is strong. Everything else in the trans works perfectly. I've had this since I got the truck which is about 4 years ago, but I've always wondered if this was something easily fixed like a broken spring or leaking o-ring (one of those oil tubes handles first/reverse brake I think?, does it have o-rings?)

I've seen a few posts about this, but never any resolution. Before I pull the pan, I'd like to know if there is anything common I should be looking for. I'm really not interested in tearing everything apart and rebuilding since the 3 second delay is something i can just deal with until something more goes requiring a rebuild but if its something i can fix just by pulling the pan, I'm game.

I do have another XJ that I've compared it to and this is the only thing different with the trans...
 
the only think i know is that reverse is controlled only by the shift lever. and nothing electronic.

have you changed the fluid recently?

does it get any quicker if you rev the engine a little higher than idle.

what year is the jeep? it may just benefit from a filter screen replacement and some new fluid.
 
It did have a filter and fluid change when i first got it. I will test revving and going into reverse tomorrow. I believe it takes same time to engage regardless of RPMs.
 
You might try adding a bottle of LubeGard in the red bottle to the
transmission. If a valve is sticking, that may loosen it up after a while. The LubeGard is not snake oil, it really works. I've used it
in all my transmissions for years.
 
Well I'm trying to find clarification on what components actually control the first/reverse brake. The manual shows it, but doesn't mention what solenoids, accumulators, etc are involved.
 
The FSM mentions timing how fast drive and reverse engages. It says:

Engagement time in D range should be a maximum of 1.2 seconds. Engagement time for Reverse should be a maximum of 1.5 seconds.

TIMELAGTEST ANALYSIS
If engagement time is longer than specified for D
range, check for the following:
• shift cable misadjusted
• line pressure low
• forward clutch worn
• overdrive clutch worn or damaged

If engagement time is longer than specified for
Reverse, check for the following:
• shift cable misadjusted
• line pressure low
• direct clutch worn
• first/reverse brake worn
• overdrive clutch worn or damaged
 
I have been using Trans-X for 40 years, same thing. It cleans / dissolves the gummy varnish build up that makes the valves stick. Sticking is worse when the unit is cold!!! I have fixed 3 AW4s for years, 5-8 years with it when they did that.

For now your problem is varnish, use a pint of Trans-X. It dissolves the varnish fast.

You might try adding a bottle of LubeGard in the red bottle to the
transmission. If a valve is sticking, that may loosen it up after a while. The LubeGard is not snake oil, it really works. I've used it
in all my transmissions for years.
 
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