vacuum mod or not?
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Joined: Aug 2004
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From: Richmond, Texas
vacuum mod or not? Ok, i've been looking at getting a rock-on 4l60 with vaccum mod but my local builder says thats the worst thing i could do. i've talked with the local builder about a dozen times and told him what guys on here tell me and he still swears that its a really bad idea. He builds street and full out race trannies and he's been in business for 25 years. this tranny will go in my daily driven regcab silverado 5.3 bolton. Please give me your opinions. tranny is going fast. thanks
Bryan
Bryan
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
The guy who installed my shift kit - who is really good and knowledgeable - gave me the same line about the vacuum mod. But then most of the highly respected performance builders - Rock On and FLT to name two - use it, and their trannies are known to be very durable.
Like Rev said, if you ask any of the builders that are sponsors on here they will tell you the opposite. I'm not sure why a guy thats been in business for 25 years with these things would tell you its bad. I believe that is far from the truth.
I have a vacuum modulated 4L60E as well as others on this site and there have never been any vacuum modulated related problems or failures reported.
I have a vacuum modulated 4L60E as well as others on this site and there have never been any vacuum modulated related problems or failures reported.
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Originally Posted by Greaseymec
I,ve installed several and also run one myself. No issues with the mod.
Mec
Mec
Eidt: the DTC is P0748 Pressure Control Solenoid Circuit https://ls1tech.com/forums/automatic-transmission/383128-p0748-code-sanity-check.html
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Originally Posted by Ouija
I've been using one of his vacuum modified transmissions (with a Transgo no-yoyo kit) for at least a year and other than one stupid DTC being thrown (I'm assuming due to a faulty resistor) I haven't had any issues.
Eidt: the DTC is P0748 Pressure Control Solenoid Circuit https://ls1tech.com/forums/showthread.php?t=383128
Eidt: the DTC is P0748 Pressure Control Solenoid Circuit https://ls1tech.com/forums/showthread.php?t=383128
Mec
Thread Starter
TECH Enthusiast
Joined: Aug 2004
Posts: 628
Likes: 0
From: Richmond, Texas
talked to the tranny guy again today after doing some more investigation on the vacuum mod. He says that he has had problems when he used to do them years ago with the hoses leaking, trannies acting up after people change to a bigger cam, something about it leaking in the case, etc. After reading some of the threads im not so sure about the mod because i have read of several people with problems with leaking hoses, the wrong kind of hoses being used by the installer, and higher line pressure due to bigger cams. I've got to have a daily driven vehicle that i can beat the mess out of without having to deal with/worry about a vacuum leak. Is it possible for me to program the computer in a way that will help the tranny last longer or does everyone believe that the vacuum mod is still the way to go. thanks,
Bryan
Bryan
well of course if a cam alters your vacuum it will alter your line pressure if you run vac-mod, with the whole hose leak thing, you already have plenty vacuum hoses on the motor already, so it cant be impossible to fix a vacuum leak from a hose, i'd count that as a minor problem if it ever occurs...
Lol...i cant believe you are still questioning this. The 2 big dogs on this board..RockOn and FLT use vac mod and you are wondering. Get local yahoo to build you a tranny...save some money...blow 3/4 clutches and then while you are down, you can save money to get a good tranny with the vac mod.
Do YOU make over 600 ft lbs, or intend to?
In the Fbody, trans programming can modify anything you want about shifts... I beat the hell out of my fbody (nowhere near 600 ft lbs) with no vac mod, just slightly firmed up pressures and shift timing in the program. It does have internal modifications, including a billet servo and MUCH smaller accumulator, which assist in fim shifts. Modding for future cams and or stall converters is trivial in programming.
IMHO, any trans shop that claims to do performance transmissions for late model vehicles, but does not realize what can be done, or how to do it, with electronic controls needs some reschooling. The 60s are over, Elvis is dead...
If you want to give up on electronic controls, there are LOT of stronger transmissions out there than the 4L60E, which tend to be a LOT less expensive to build and build up.
In the Fbody, trans programming can modify anything you want about shifts... I beat the hell out of my fbody (nowhere near 600 ft lbs) with no vac mod, just slightly firmed up pressures and shift timing in the program. It does have internal modifications, including a billet servo and MUCH smaller accumulator, which assist in fim shifts. Modding for future cams and or stall converters is trivial in programming.
IMHO, any trans shop that claims to do performance transmissions for late model vehicles, but does not realize what can be done, or how to do it, with electronic controls needs some reschooling. The 60s are over, Elvis is dead...
If you want to give up on electronic controls, there are LOT of stronger transmissions out there than the 4L60E, which tend to be a LOT less expensive to build and build up.
Originally Posted by ohohsilverado
thanks cable, i am a worry wort. just aint got the money to keep rebuildin trannies
Your stock unit has 8-11 external (to the transmission) controllers that have an effect on line pressure...with the Vac kit you have a modulator, pin, and valve...
Let’s say the hose leaks...okay ...so you have max line pressure whats wrong with that?? leak in the internal hose...change the hose and go on down the street..
How many guys do you hear on this or any other board complain of theses kits?? How many have problems?? Maybe an occasional it’s hitting hard.
There are allot of folks out there that have been doing something for 25 years...have been successful at it.....that doesn't mean it's better...your guy is in his comfort zone...and you'll not remove him from there.. We use them because it’s the best system available for what we are doing….I haven’t always thought this way not using them set us back 5 years… Hope this helps..Dave
yeah but when do you have low vacuum...mainly at idle and who cares what line pressure is at a redlight.
I wasnt trying to come down on ya. Read this section and see how many have 2-3 shift problems etc. Most of that is tuning related. Vac mod gets rid of a lot of those variables.
With vac mod you get consistant line pressure rise....quick...and a ported maf...miscalibrated maf table etc wont screw with that. all electronic can be very effective but for builders, how many want to take the chance that you know exactly what you are doing with your tune. I wouldnt. I myself have messed with the line pressure tables and damn near burnt my tranny up going around the block when it was stock. Trust the PROs...vac mod...good quality build and spend your weekends racing or cruising....not pulling out another economy rebuild. Give Dave at RockOn a call...he will shoot you straight.
I wasnt trying to come down on ya. Read this section and see how many have 2-3 shift problems etc. Most of that is tuning related. Vac mod gets rid of a lot of those variables.
With vac mod you get consistant line pressure rise....quick...and a ported maf...miscalibrated maf table etc wont screw with that. all electronic can be very effective but for builders, how many want to take the chance that you know exactly what you are doing with your tune. I wouldnt. I myself have messed with the line pressure tables and damn near burnt my tranny up going around the block when it was stock. Trust the PROs...vac mod...good quality build and spend your weekends racing or cruising....not pulling out another economy rebuild. Give Dave at RockOn a call...he will shoot you straight.
Typically the cam will not allow as much vacuum to be created therefore your base pressure will be greater than with a higher vacuum pressure.
Here goes… No Vacuum or Low Vacuum = Max line pressure or higher line pressure….Hi vacuum = Low line pressure , it’s a sliding scale as foot travel on the accelerator increases vacuum decreases…thus line pressure increases..
Where we get into trouble is when line pressure doesn’t match (or equal) foot travel. Your foot is in the throttle and your computer (for whatever reason one of those 8 to 11 controllers is acting up or a bad tune) isn’t telling the EPC to increase line pressure. Now your up in the higher hp level, with low pressure…. the clutch doesn’t have enough clamping (line) pressure to hold the hp going through the clutch thus it slips, then burns
So if you were getting 14 lbs of Vac….you were running lets say 70 psi line pressure…now you changed cams and are only getting say 10 lbs of Vac. Well your line pressure increased to say 90 psi…so you’d be starting out with a higher line pressure than before. (These are not actual numbers simply put out there for demonstration)
As these cars and trucks age we are going to see more problems with these electronic systems, and it doesn’t seem to matter weather you’re dealing with 300 hp or 600 hp. The more horse power the more line pressure is needed and this system delivers the goods.
I hope this helps...Dave
Here goes… No Vacuum or Low Vacuum = Max line pressure or higher line pressure….Hi vacuum = Low line pressure , it’s a sliding scale as foot travel on the accelerator increases vacuum decreases…thus line pressure increases..
Where we get into trouble is when line pressure doesn’t match (or equal) foot travel. Your foot is in the throttle and your computer (for whatever reason one of those 8 to 11 controllers is acting up or a bad tune) isn’t telling the EPC to increase line pressure. Now your up in the higher hp level, with low pressure…. the clutch doesn’t have enough clamping (line) pressure to hold the hp going through the clutch thus it slips, then burns
So if you were getting 14 lbs of Vac….you were running lets say 70 psi line pressure…now you changed cams and are only getting say 10 lbs of Vac. Well your line pressure increased to say 90 psi…so you’d be starting out with a higher line pressure than before. (These are not actual numbers simply put out there for demonstration)
As these cars and trucks age we are going to see more problems with these electronic systems, and it doesn’t seem to matter weather you’re dealing with 300 hp or 600 hp. The more horse power the more line pressure is needed and this system delivers the goods.
I hope this helps...Dave
Last edited by Rock-On; Jul 24, 2006 at 07:32 PM. Reason: typo
But at what point is too much pressure? If you guys set up a tranny to run within a certain PSI range and a user installed an aftermarket camshaft that increased the pressure quite a bit, would it be bad for the transmission that it is now out of your spec?
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
Originally Posted by ohohsilverado
After reading some of the threads im not so sure about the mod because i have read of several people with problems with leaking hoses, the wrong kind of hoses being used by the installer, and higher line pressure due to bigger cams. I've got to have a daily driven vehicle that i can beat the mess out of without having to deal with/worry about a vacuum leak.