The reason I use the vacuum modulator is that I can get a higher line pressure (225-235lbs), while still having the lower line pressure at light throttle openings, it is faster than the EPC solenoid in response time to raise line pressure when there are changes in the throttle position, allows for almost instant downshifts, instead of the delayed downshifts that are common to this unit, and is not subject to the electronic fluxuations (spikes)that can happen, etc. You should put 2 straps on each end of the vacuum hose that sits inside the transmission, this will do a better job than the single strap on each end as per instructions. On the 10 or 13 vane setup; if the pump came with 13 vanes, you can go either way, you must use the 13 vane slide here. If the original pump has 10 vanes, you "cannot" change to a 13 vane setup as the stator half of the 13 vane has different oil transition slots that do not exist on the 10 vane stator half, and it will cut down on the volume of oil. If you use the Trans-Go Performance Shift kit, do not add any spacers to the 2nd accumulator. You want smooth shifts at part throttle, and not too firm, and at WOT you want quick & firm shifts. I modify the Trans-Go Performance Shift kit to do more than it offers "as is". With the 4,400 stall can do more.
On the 10 or 13 vane setup; if the pump came with 13 vanes, you can go either way, you must use the 13 vane slide here. If the original pump has 10 vanes, you "cannot" change to a 13 vane setup as the stator half of the 13 vane has different oil transition slots that do not exist on the 10 vane stator half, and it will cut down on the volume of oil.
Ok, I have/had a 13 vane pump stator and before it decided to split into 3 pieces this pump lasted ~3 years, 20k, with 50 track passes. Luckily none of the pieces had time to migrate and cause havoc elsewhere. So what are the pro's and con's provided you know you had a 13 to begin with and can choose?
If you want more volume out of the original 13 vane setup, you can change over to the 10 vane. Go with the Trans-Go steel rings and hi-rev priming spring instead of the stock rings & spring. This will ensure that you have volume & oil pressure all the way to 7,800 rpm. Overkill, but it is safe insurance against losing volume & oil pressure.
Ok though I do know that some will disagree here is why we do not use the vacuum modulation setup in our units.
1- though it may be considered rare modulators do fail as do PCS however when a modulator fails it may and usually does leak and trans fluid may be sucked right into the engine.When a PCS fails you simply have low line and though this to can cause damage if addressed immediately it not a problem and it very noticeable it has happened by the poor shift quality, The modulator after failing shift quality would remain unchanged more or less except for the loss of fluid which you may not be aware of till there isn't enough fluild
2- The PCS is a more effective way to accurately control line pressure and is not affected by large cams and low vacuum like the modulator would be causing higher than necessary line at low speeds which causes unnecessary impact on hard parts in non performance driving situations increasing stress and wear.
With the proper ungraded spring added the PCS at WOT and 0.0 Amps has no alternative but to make the max line thats possible with the unit just as the VAC mod will with 0 vacuum, So we do not feel there is any advantage there either.Though both do work in that area in the same manor and make max line,
3- The vacuum mod was introduced for use in the 4l60e and the 4l80e when there was no ecm to control line and the transmissions had been set up for full manual with no ecm , Particularly for the 4L80E before controllers were readily available not because they were a better idea but because they were practical and inexpensive solutions to running max line on the full manual trans only and again beating it to death unnecessarily, The vac mod was a good idea in its day with the TH350 and others because it was the best technology at the time. But the newer ways of controlling transmissions electronically instead of with cables and vacuum mods are considerably better otherwise I beleave GM would have stayed with them to since they don't spend money for nothing and millions developing ECMs and the comparably more expensive PCS would not have been done if the older and already developed modulators were as good or reliable.
Thats our opinion though I'm sure some will disagree on the modulator modification for the 4l60e but thats ok thats what makes us all different
The vacuum modulator is what GM decided to use at the time in the mid 1960's, and Mopar never used vacuum modulators on their 727/904's, so it was just a different approach, and guess what both worked. The large cams do pull lower vacuum at very low speeds, which does result in higher line pressure, but once the "Revs" start, about 2,500 rpm the larger duration cam will start to pull vacuum very quickly, and I modify the accumulation so as not to have bang shifts at part throttle. On all of my TH350/400's in the past with large cams, they did well on all shifts, sometimes you had to change the modulator settings, or use a different modulator all together, but they worked well when setup correctly. The vacuum modulator has a wider range in terms of low to max line pressure, as compared to the force motor. Even Ed Wright at www.fastchip.com uses the vacuum modulator, (because of reasons already stated) on his low 10 sec. 1996 Firebird, and recommends it to others. Each to their own here, if you are satisfied with the approach you are taking, and get the results you want, then great. What I do not like is someone saying (not you performabuilt, but a couple of others) that vacuum modulators do not work and will destroy your transmission if you use them, nothing could be further from the truth here. It is just another approach to getting things to work the way you want. If they did not work, how is it I have a few 10 sec. and a high & low 9 second 4L60E vehicles doing very well with the vacuum modulation setup.......
Thats why I said to each there own I too have seen both setups doing well in high powered cars , Though I personally think the PCS is the better way even I could play devil advocate and argue the pluses to the modulator also. I don't trash the way anyone builds there transmissions as long as they are working well and holding up for them. But did want to explain the other perspective on them.
interesting. well it will not be untill the summer till i do this. with almost 90xxx on the car, money is getting more and more abundant. so its time to start modding. and i really dont need my trans going out on me.
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Actually it can go either way and electrical failure would cause max line where as the more worrisome mechanical failure can cause min line , Unfortunately the electrical failure is less common to the mechanical getting stuck open with debris or a screen failure (screen come apart and get in the solenoid )but both do happen hough generally the mechanical is usually associated with excessive debris which probably means theres a much more serious problem in the trans to start with. But in eithr case on one hand you get and extremely harsh shift and the other very very sloppy but in neither will there be any fluid coming up vacuum line.
Now it might be said that debris wouldn't affect a modulator and thats true but the problem causing them would still be there
I have had one vacuum hose go bad in the last ten years, and the fluid he used had more than the normal amount on seal softener in it. It was not a name brand. I install 2 ties on each end of the vacuum hose that sits in the pan, and recommend a good quality fluid. This is the down side.
I have a little different setup on my vacmod units that doesn't use the cheesy little zip ties supplied along with the case fitting supplied. I to seen some issues with the vac mod kit however I have modified it. When I'm done you can pick an empty 4l80e case off the ground. I do build these units with or with out the EPC however the feedback with the vac mod setup has been very good. Also I have found that the gauges on the Dyno stay much more constant with the vac mod units. I really have done alot of research in the last couple of years to minimize this flutter with epc controlled units and will build them both ways. Most people in my opinion that only use EPC's are just scared. Vince
I have used both set ups and both worked fine , What I didn't find was any significant difference in performance that would justify the additional price people charge for this mod , We are not afraid to use them just see no reason to, If someone eally wants one that bad then we will get them a price on it, But I will also tell them that they should use the extra money to go fill there NOS bottle instead, But its all in opinions I dont think modulators are bad for the tranny in particular but i also dont see a major advantage either