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Daniel Wilson
Daniel Wilson,
Category: Transmissions
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Experience:  Owner at DJ Wilson
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Just did a rebuild on 4L80e trans. I now have very little

Customer Question

Just did a rebuild on 4L80e trans. I now have very little reverse and also trans fluid has spewed fron fill tube
JA: Tell me a bit more about what's going on so he can help you best. Are you hoping to fix this yourself?
Customer: Yes. Tranny was starting to slip slighly and shifting from first to sencond was kinda hesitant
JA: Great! What have you tried so far?
Customer: Unplugging the main sensor at valve body and thats when i got a slight reverse action
JA: Is there anything else the GM Mechanic should be aware of about your GM?
Customer: It has over 400,000 original miles
JA: Our top GM Mechanic is ready to take your case. Just pay the $5 fully refundable deposit and I'll fill the GM Mechanic in on everything we've discussed. You can go back and forth with the GM Mechanic until you're 100% satisfied. We guarantee it.
Submitted: 11 months ago.
Category: Transmissions
Expert:  thomas hill replied 11 months ago.

hi my name is ***** ***** the fluid all foamy?

Customer: replied 11 months ago.
No
Expert:  thomas hill replied 11 months ago.

it drives forward ok?

Customer: replied 11 months ago.
I only have second gear. I just discovered this when I drove the truck
Expert:  thomas hill replied 11 months ago.

so the fluid coming out of dipstick tube you may have pinched the vent line putting in the trans. that will push fluid out the dipstick tube

Expert:  thomas hill replied 11 months ago.

are you getting any codes for the trans

Customer: replied 11 months ago.
No codes.
The fluid spewed out before i did the rebiuld and again after. I thought of the vent tube also and checked it first and it was clear.
Expert:  thomas hill replied 11 months ago.

did you rebuild the pump?

Customer: replied 11 months ago.
I did not rebuild the pump
Expert:  thomas hill replied 11 months ago.

I'm thinking that your trans pump is sucking a lot of air and pumping it into the trans pushing out the fluid and air rating the fluid so the trans can't hold pressure

Customer: replied 11 months ago.
Where would it be getting air from. I've seen no evidence of air bubbles in the fluid
Expert:  thomas hill replied 11 months ago.

when it goes into 2 is it strong in that gear

Customer: replied 11 months ago.
seems to be very strong
Expert:  thomas hill replied 11 months ago.

after looking at the diagram you may have a problem with the low reverse band did you seat it on the locking pin good sometimes they can pop off during install

Customer: replied 11 months ago.
It snapped in veey good.
Just to make sure second is the only gear i have. The trans does not start out in first it starts out in second and does not shift up or dowm shift
Expert:  thomas hill replied 11 months ago.

I'm going to open this up to other techs i don't think i can help you

Expert:  Daniel Wilson replied 11 months ago.

Hi my name is***** will be glad to help. Is reverse the only gear you have trouble with and is this the only gear oil leaks out of the fill tube?

Customer: replied 11 months ago.
I only have a very very slight reverse motion. I only have second gear. The trans does not start out in first it only has second gear. It does not up shift from second and does not down shift to first.The fluid spewed out while trying to fill trans to proper level . It was like a big burb. This aldo occurred prior to the rebuild.
Expert:  Daniel Wilson replied 11 months ago.

Click on this link for the pressure testing and specs for this transmission.

Troubleshooting

Expert:  Daniel Wilson replied 11 months ago.

see page 4 for your pressure test information. See what you have for actual pressures. did you do anything with the pump or converter? What type of rebuild did you do? what was replaced?

Customer: replied 11 months ago.
New converter and ran a pressure check. Everthing seemed normal except rever
Expert:  Daniel Wilson replied 11 months ago.

Thanks for the update. What are the actual pressures you got?

Customer: replied 11 months ago.
Around 50 psi in or out of gear. I did put it in gear and held the brake, the pressure went to 150 psi or so. Which according to the manual thats whith in specs
Expert:  Daniel Wilson replied 11 months ago.

did you open up the valve body and clean and inspect all the valves? Test all the solenoids an pressure switches/pressure control valve? If not I would go there next. The test specs are in the link I posted. Also see if pressure drops off in reverse. Reverse pressures are higher. 60-70 at idle and 300-330 at high RPM

Expert:  Daniel Wilson replied 11 months ago.

Did you write down what you had in all gears? Just wondering what the pressures are in each individual clutches. Need to know for troubleshooting. Let me know

Customer: replied 11 months ago.
I have the valve body out of trans at the moment as soon as i can get it back in I'llgo back thru the pressure check and have to back with you
Expert:  Daniel Wilson replied 11 months ago.

Ok sounds good. I log in as I am able in between jobs, evenings , etc.

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