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  #1  
Old 12-05-2005, 03:41 PM
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Transmission oddity

I accidently left the modulator line unplugged after an oil change last night and it's shifting better! The 1-2 isn't as firm and the 2-3 doesn't have a breif pause before shifting. When I adjusted the modulator last summer all the shifts were affected and I had to find the best level of jerk and slip together. The only problem is now I have an upshift clunk at low throttle. I'm thinking about hooking it back up but turning the vac way down at the bleed valve. Strange how it's affected. This is on a brand new Sun Valley rebuild with 5000 miles on it.

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  #2  
Old 12-05-2005, 07:03 PM
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You may have a slight vacuum leak in the modulator and other area that is bleeding off. A properly functioning modulator circuit will give a crisp but not FIRM shift. It should NOT feel like a Camaro with a shift kit.
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  #3  
Old 12-05-2005, 10:12 PM
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The 3/2 valves are disconnected and the modulators almost new along with all rubber connectors. Vac pump pulls 23 in. The range is set pretty close on the bleed valve. I can't get it any better. But the 1-2 will break the tires loose on wet pavement.
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  #4  
Old 12-05-2005, 10:49 PM
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This may help:
MBZ.org trans. adj. condensed

--------------------------------------------------------------------------------

Remove the vacuum line at tee of large vacuum line from pump to booster. Take a wire or 1/16" drill bit and ensure opening is clean of carbon, etc... (Vacuum @ tee @ idle = 21-23in/Hg) if not, vacuum pump check valve is suspect.

@vacuum regulating valve on IP. Lever w/ linkage to IP. @ full throttle, clearance from flat on lever and stop pin = .5mm. If not adj. linkage.

Check the vacuum levers on valve cover for leaks w/ mightyvac.

Disconn. kickdown cable. Pull on cable to point where slack disappears. @ this point, the cable and ball joint should mate. Adj. cable to obtain.

@ tee of regulting valve, disconn. black line to vac. mod. on trans. Apply vac and leak test modulator for at least 5 min.

Conn. vac. ga. at tee where black line was. Chk for vacuum @ idle. Disconn. linkage to regulating valve and IP. W/ eng. @ idle move lever to full throttle. Vacuum should drop to nearly zero.

Measure a distance of 10mm between stop pin and lever. (use 10mm wrench, etc..) @ idle vac reading = 5.5(harder, later) to 6.5(softer, earlier) in/Hg.
To adj. remove dome-shaped cover on regulating valve. Once removed you'll see the shaft from the lever along with a locking nut. Loosen locknut and adj shaft which has two flats on it. CAUTION: 2-5 deg rotation makes a significant change.

Reconn. linkages and vacuum lines. Road test.
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  #5  
Old 12-06-2005, 06:39 AM
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I've been through it all. I was simply commenting on how strange it is that I got a softer 1-2 with no vac and a harder 2-3. All my vac to the trans is perfect.
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  #6  
Old 12-06-2005, 08:27 AM
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Quote:
Originally Posted by rg2098
I've been through it all. I was simply commenting on how strange it is that I got a softer 1-2 with no vac and a harder 2-3. All my vac to the trans is perfect.
that is indeed really strange. And since you do get strong shifts, it makes sense that the relatively new trans is OK too. here's a weird longshot for ya - any chance at all that the vacuum pump puts out a strong vacuum at idle (only time I've ever checked mine) and then drops, even pressurizes slightly due to a bit of blowby and something funky with one or more of the vacuum check valves?
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Old 12-06-2005, 11:06 AM
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Nope, pumps checked out good. My engine doesn't have that much blowby gases but it does like to soak the air filter.
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  #8  
Old 12-06-2005, 11:56 AM
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Quote:
Originally Posted by rg2098
Nope, pumps checked out good. My engine doesn't have that much blowby gases but it does like to soak the air filter.
And does the vacuum stay up even when you are driving down the road? I admit I've never measured mine like that, but it's easy enough to do.
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  #9  
Old 12-06-2005, 01:44 PM
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Never checked while driving. It does hold while free reving the engine.

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