Hi ya folks.. I recently discovered that my vacuum modulator on my stock Autotransm. (Buick Riviera 66 mod, Super Turbine 400) is leaking.. So I'm wondering if it's a straight swap?? No need to separate Autotrans. from engine?? And I'm trying to locate a replacement modulator.. Will this do the trick? http://www.oldbuickparts.com/catalog/product_info.php?cPath=19_32_129&products_id=1262 Any "pointers" would be appreciated... Sturla
Is your vac mod really leaking (internally), or does it just need a new O ring (external) where it slides in? A vac mod replacement is easily available, and usually adjustable, but not altitude compensated like the original. You can expect to lose a lot of trans fluid when it comes out, unless some is drained and/or the car is parked on a big slope. Bruce Roe
Sturla, You might get some fluid pouring out the port when you remove the old one. Have the new one in hand ready to shove in right away. You might want to jack the right side of car up to shift the fluid to the opposite side of transmission to prevent it from pouring out when you pull the old one. This is a very simple job. Note the one you see pictured on CARS website is not what you will receive. There is a much smaller one that is a direct replacement and it is also adjustable and thats what you will get. I have not been able to locate an original looking replacement modulator anywhere.
Standard Motor Parts TM17 is the larger modulator. It should work fine in any THM350 or 400. You can adjust the larger modulators, you just need to use some sealer around the adjusting screw when you are done so that it doesn't leak vacuum.
Larry, I saw that one but Rockauto lists it as being for a 2 speed ST300. Any other listing I looked at for the TH400 showed the smaller style. Rockauto shows the smaller TM15 as being for the 3sp TH400. Do you know for sure the TM17 would work on the 400? Thanks
I can't think of any reason why it wouldn't. The adjustment screw is sealed with silicone. Once you break the seal, they adjust. You just need to apply silicone sealer around the screw, otherwise, it leaks vacuum past the threads.
If it is the small brass ones, they are adjustable. It might not need it though. I would road test the car and see. You can check the minimum throttle shift points. Should be 9-12 MPH (1-2), and 20-25 MPH (2-3). You can adjust the shift point and feel by 2-5 MPH. For later harder shifts, turn the screw (inside the vacuum nipple) in clock wise. For earlier softer shifts, counter clock wise. Don't abuse the adjustment CCW though, you can lower line pressure too much.
