Modulator Valve on Bonneville

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  #1  
Old 12-01-02, 12:33 PM
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Modulator Valve on Bonneville

Mechanic brother says replacing a modulator valve on a 90 Bonneville is a 5 minute job. Hubby not sure he wants to try it. (Transmission is losing fluid and rough shifts, bumps, etc) Can't find any diagrams, etc. Should I get a Haynes/Chilton book and do it myself. Brother says shop might charge $100 for such a simple job.
Any thoughts?
 
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Old 12-01-02, 02:04 PM
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Can you see where the fluid is leaking from? Engine size and transmission info would be very helpful.
I'm not sure if the '90 Bonneville has a vacuum modulator. Check out any posting from Joe F and go to one of the links he's referenced.
 
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Old 12-01-02, 02:24 PM
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Fluid does not appear to be leaking, which is why we think it is being blown out. It does have a modulator valve. Picked one up while ago. Brother said it was a 5 minute job, but he neglected to say it takes 20 minutes to jack the side up and get to the [email protected]!
So, part's there and not in yet.. too dark and too cold.
 
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Old 12-01-02, 02:25 PM
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engine is 3.8 V6. An LE, so what does that make it transmission wise? (Where do I find that?)
 
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Old 12-01-02, 04:28 PM
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All first gen FWD (87-91) Bonnevilles use a THM440T4 4 speed overdrive trans and it has a modulator.

This is one crappy transmission, riddled with problems. Try the modulator and a fluid and filter change. If that doesn't help, likely internal tranny failure.

Yes it's a 10 minute job. Check the autolibrary.org link in my signature file below for the R&R instructions---it should be there.

Why not just have your brother do the install?
 
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Old 12-01-02, 04:35 PM
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Brother is 1 hr away and snowed with rebuilding our blazer and a duelly(how do you spell that?) for his boss. He will do it if we can get the car to him or if he finishes the blazer frame/body work this week and brings it to us.
Local transmission shop is rebuilding/replacing my transmission in my 90 GMC Suburban Starcraft conversion I first mentioned last month- transmission ended up throwing a gear and totally breaking down on me last week- and they should put this modulator in for free IMO when I go by there Tuesday.
 
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Old 12-02-02, 10:04 PM
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If I recall correctly, you don't have to jack the vehicle up at all. The modulator can be changed from under the hood. Look for a metal vacuum line running to the front of the tranny, about halfway up the unit and maybe 10 inches from the engine. That line goes to the modulator. The modulator should just be held in with a small bolt and clamp. Easy cake walk.
 
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