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post #1 of (permalink) Old 01-03-2005, 08:02 AM Thread Starter
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Transmission Modulator ? UPDATE

Hello and happy new year to everyone.
I posted up a question last week in regard to "dissapering ATF fluid in my Trans" I have a Turbo 350 behind a 305, and in front of a NP205.
Thanks to the help of this board I have discovered that the Vacuum Modulator is bad. I pulled the Vac line of the modulator, and it was full of fluid.

I have looked in my repair manual, and found nothing about the Modulator, and I have not a clue as to the procedure to change this.
I was hopping that someone might be able to point me in the right direction, maybe even be able to provide a write up.

Is this somthing I can replace without pulling the Trans? How much should I expect to pay for the new Modulator? How much time should I expect the replacement to take.
This will be the first time I have ever worked on an Automatic trans. Every other Jeep I have had, has been a standard.
Thanks for any help, sorry for the somewhat vague question.
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post #2 of (permalink) Old 01-03-2005, 08:40 AM
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Re: Transmission Modulator ?

The last TH350 I worked on, the modulator was easily replaced without pulling too much apart. The modulator was cheap ( sorry I don't remember the price ).

Have you considered a cable modification to replace the VM?
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post #3 of (permalink) Old 01-03-2005, 08:48 AM
 
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Re: Transmission Modulator ?

Nothing to it.
No disassembly required.
There is a hold down clamp with a bolt. Just unbolt it and remove the modulator. You may have to wiggle it some (OK, maybe a lot) to get it out. There is an o-ring on the end that sticks into the tranny hsg that may be kind of hard or stuck by now.
Watch when you pull it out. There is a spring loaded shuttle valve behind it. This is what the modulator operates. It "shouldn't" come out with the modulator, but it might.
You will loose a little fluid when you pull the modulator, but not too much. While you are at it. Ya might want to consider changing the fluid and filter while you are down there.
If you are gonna make a mess anyway...
[img]images/graemlins/smile.gif[/img]

Price? They are pretty cheap. W/O looking, I would say less than $10.
If you have access to a tranny shop, you may want to check with them. The AP store will have it all pretty in a fancy box and priced accordingly. When I worked at a tranny shop, we bought them by the gross and they were about a 1/3 the price to buy from the AP store.
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post #4 of (permalink) Old 01-03-2005, 10:05 AM
 
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Re: Transmission Modulator ?

[ QUOTE ]
Price? They are pretty cheap. W/O looking, I would say less than $10.
If you have access to a tranny shop, you may want to check with them. The AP store will have it all pretty in a fancy box and priced accordingly. When I worked at a tranny shop, we bought them by the gross and they were about a 1/3 the price to buy from the AP store.


[/ QUOTE ]
I don't know if it's relevant or not but USED TO BE, when you replaced those units you needed to know the color code on the modulator to get the proper vacuum pull for the unit to operate. I have seen some replaced that had an adverse effect on the shift times in relation to RPM's on the motor. I have also seen them replaced at random and not have any ill effects. Just something to conceder.
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post #5 of (permalink) Old 01-03-2005, 10:27 AM
 
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Re: Transmission Modulator ?

[ QUOTE ]
[ QUOTE ]
Price? They are pretty cheap. W/O looking, I would say less than $10.
If you have access to a tranny shop, you may want to check with them. The AP store will have it all pretty in a fancy box and priced accordingly. When I worked at a tranny shop, we bought them by the gross and they were about a 1/3 the price to buy from the AP store.


[/ QUOTE ]
I don't know if it's relevant or not but USED TO BE, when you replaced those units you needed to know the color code on the modulator to get the proper vacuum pull for the unit to operate. I have seen some replaced that had an adverse effect on the shift times in relation to RPM's on the motor. I have also seen them replaced at random and not have any ill effects. Just something to conceder.

[/ QUOTE ]


Good point. GP'n You are exactly correct.
Thanks for the reminder.
There is (or was) a coloured stripe on the modulator to ID it. IIRC - the Red Stripe is the most common.
The ones that you get from the tranny shop are usually adjustable. Small screw (hex or flat tip) inside the nipple.
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post #6 of (permalink) Old 01-03-2005, 03:52 PM Thread Starter
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Re: Transmission Modulator ?

Wow, what a relief. I was worried that fluid pan would need to come off, and that getting the VM out was going to be a real project.
It sounds like the best thing to do would be to pull the old one out and bring it with me to the parts store... So I can get the correct color. That will make it a little harder to get it done all in one night, but it sounds like it is a much easier project than I thought it would be...

Does anyone have a good link to an exploded view of a T-350. Or maybe a pic that shows were the bolt is that holds the retainer that holds the VM in there. Because of my cross member I am going to have to do most of this project by feel.

Leve. I would be interested in more about the cable conversion you speak of. I have never heard of that.

Thanks again for all the help.
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post #7 of (permalink) Old 01-03-2005, 08:38 PM
 
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Re: Transmission Modulator ?

I'm currently rebuilding my TH400 and here are a few pics from the manual I'm using to rebuild the tranny.

I tried to get the image inside the post, but couldn't figure it out, so here is the first one.

See attached.


Hope this helps.
Attached Images
File Type: jpg 1375051-mod1.jpg (49.1 KB, 34 views)
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post #8 of (permalink) Old 01-03-2005, 08:41 PM
 
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Re: Transmission Modulator ?

Here is the other image.
Attached Images
File Type: jpg 1375053-mod2.jpg (53.9 KB, 35 views)
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post #9 of (permalink) Old 01-04-2005, 06:30 AM Thread Starter
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Re: Transmission Modulator ?

Pulento
That was just want I was looking for, thank you very much.
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post #10 of (permalink) Old 01-04-2005, 06:43 PM
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Re: Transmission Modulator ?

I had the same problem one time and I'm sure this might be bad advice but leave it unhooked.

plug it off. it will shift a little harder but you might like it, then change it when you have time

Clint
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