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Sonnax 545RFE Line Pressure Booster

81K views 212 replies 64 participants last post by  MidwestJ 
#1 · (Edited)
Just wanted to throw this out there,

But I got mine in and this thread will help people "searching" for answers to the Sonnax piece!

I have had mine in for two days now, along with

BlackRamHemi...bad @$$ black reg cab (please chime in) :)

and we both are very happy with the shifting results. I cannot speak for the few that have bad things to say about these pieces....but I can't confirm their claims either, because....

My truck shifts WAY better with the Sonnax in! I found tons of happy owners on the D T forum, so I went for it, and will never look back! :)

Edit: Here is the install.......passenger side of the transmission at the back corner of the fluid pan...single connector behind the y-pipe / heat guard plate! The Sonnax just clips between the transmission and the stock wire...only one way to do it!

 
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#136 · (Edited)
I was able to obtain one from sonnax at sema and for the first couple weeks I could "feel" the difference on my daily drive to work. After a few months now it feels the same as it did before I put one in. I use to be able to feel the firm shift and now its just a smooth shift like before. At this point I may remove mine just because its not really gaining anything but its not hurting anything either so I might as well do without as i'm not out any money on it. Just sharing my experience.
 
#138 ·
So....I've been doing some experimenting, and found some interesting (although not conclusive) results. All the tests were run with NO trailer and minimal payload.

I removed my tune and the Sonnax...at the same time. Truck ran like garbage and shifted ultra sloppy for about 1 minute, then started to sort itself out. The shifts were ultra smooth, and the shift time was IMO quite long. I kept it like this for a couple of days, >100miles and 15+ start cycles. On the 3rd day, I reverted to manual shifting and aggressive driving. Within a few minutes (3-4 starts from a dead stop), the trans started to shift a bit more aggressively and faster, and the engine seemed happier. I kept this up for a couple of days with a good mix of city/highway and many start cycles.

I then installed the Sonnax and immediately noticed a difference. Shifts were fast and firm.....for awhile. After 5 starts cycles and 30+ starts from a red light, I noticed the shifts were decreasing in firmness. By the end of the first day, it felt like I have never installed the Sonnax unit at all!! :wow: Didn't matter whether I ran easy or aggressive, the results were about the same as without it.

I then removed the Sonnax unit, and trans shifted terribly (even noticed a bit of slippage) for about 2 starts from a dead stop. Then it was back to 'normal'.

Next day I installed my 91 tune, which was really noticeable! The trans seemed to shift firmer, so I drove like granny for 2 days, and although it softened slightly, it never got as soft as without the tune. I then switched to 'lets have fun mode' and after a few minutes manual shifting, etc. it firmed up, and sped up slightly...but noticeable.

I then installed the Sonnax, and the first shift out of the lot broke the tires loose. Now that's not very impressive when you consider how slippery the roads are, but was certainly much firmer than it was 5 minutes before that.

I have left it in that configuration since, and the soft shifts after 'granny driving' for a couple of days (That was really hard to do when all you want to do is drive 'normal'), were firmer then the firmest shift attained in 100% stock mode. When I then opted to drive 'my normal', the firmness of the shifts returned within minutes.

In conclusion - I have absolutely no idea what is all happening, but believe the tuner is affecting the transmission, and under the conditions I present to my truck with my driving style, the Sonnax unit is making a difference that pleases me. But it only appears to do so when I have a non-OEM tune in the PCM. :4-dontknow:

With the tune out of the system, I experienced results that fully support what TransEngineer mentioned about how the trans will adapt.

I'm looking forward to further experiments this summer that will hopefully include a comparison between SuperChips and Diablo. It is my understanding that SC allows for some trans modding that is currently not available to me with my current tuner. I also hope to install a mechanical trans pressure gauge to see what is actually happening. :)
 
#139 ·
SO in short stay away from the sonnax with a tune thats what killed my tranny about a year ago...
 
#140 ·
great info Brad, ive read so much with this post and the info is amazing, but i def will stay away from this
 
#142 ·
Hey Garner . What happened to your mom's never ending check book. Doesn't she buy you anything you want???
 
#144 ·
yea alot of people here have said its pointless and the tech guy here said so too
 
#147 ·
Interesting. So it's not really worth it?

Here we go again. Caddy you know you could just PM me if you have something to say...
 
#148 ·
To me the booster didn't do jack when I was stock but I threw it back on with I got my Circle D and Headers and it seemed to help out. Maybe it's just me but my shifts were firm and when I took it off the shifting seemed to be more sloppy....even after the computer relearned. With that said I've had it on for 1 month straight and I'm happy with it...I don't think its messing up my tranny like the other guy claims it did.
 
#149 ·
Was just trying to be funny. Sorry.
 
#153 ·
To mess with line pressures with a DiabloSport, you need a CMR tune. It's not in the canned tunes.

The first few shifts with the Sonnax will hit hard, but the computer smooths them out...then if you take it off, the will be way soft and slip.
 
#154 ·
So should I just take out my sonnax and put it beside my throttlebody spacer in my random nonsense drawer in my tool box? Or just leave it in since its not hurting anything really?
 
#160 ·
With my DS tune, the Sonnax is both noticeable and the shifts don't seem to 'adapt' as they do without it. Even if I granny drive for awhile, they stay firm. Without the tune the PCM appears to adapt to the Sonnax and reduces the pressure.

I am hoping to hook up an actual pressure gauge to monitor what is going on, but for now I'm very pleased with the combination of DS tune and Sonnax. The shifts are firm enough to chirp the tires on both the 1-2 and 2-3 shifts on hot pavement under WOT. Without the Sonnax, that never happens. :4-dontknow:
 
#162 ·
I don't know what the DS does as far as trans tuning, but it appears that it has a preset trans tune that does not adapt. Driving style does not appear to change the way it shifts. I have no doubt that it still has the slip detection and will alter the pressure if needed to ensure no slippage, but it does not appear to reduce pressure to 'smooth' the shifts like the OEM tune does.

If the DS is capable of monitoring the pressure, I am not aware of where in the unit to do that, but even if it does, it will be taking this from the sensors that will not likely read the altered pressure of the Sonnax unit so I would like to install a mechanical gauge to read the actual.

It is unfortunate that we can't get the full low-down of what is being done in the PCM and other module.....and what the tuners are actually doing. Not that it would make a big difference, but that like tidbit of information would reduce the amount of speculation and unknowns.

I think I can safely assume that Chrysler and the tuner companies are not willing to release their source code which is what would be needed to really tell what is happening. :)
 
#163 ·
Unless you have a pre-2011 and are using a tuner. Then the sonnax makes a notable difference.
This is exactly the same experience that I have. It does not seem to return to standard pressures...what ever they are. Maybe it's the tuner...but after 1,000 miles and lots of standard driving, there is still a noticeable firmness that is just not there without the booster.
 
#164 ·
I just wonder if what you guys are feeling is the effects of the tuner, and not the line booster. There is a big difference in shift firmness with my SC vs. stock. Reduced TM and shorter shift duration make it feel firmer.
 
#169 ·
I have tried mine both with and with the Sonnax; stock and DS 91 performance tune. Just installing the DS tune makes a difference in the shift firmness that appears to be persistent. Adding the Sonnax increases the firmness and appears to be persistent as well.

When I run factory tune, the shifts are definitely smooth. So smooth that often you can't feel the shift, but rather feel the difference in engine RPM. When the Sonnax is installed, the shifts firm up, but that is only temporary in my experience. As Transengineer pointed out, the PCM will adapt and lower the pressure to smooth the shifts, and that is exactly my experience.

However, with the DS tune installed, I don't seem to gets these same stock adaptation results. The shift firmness stays regardless of how I drive, and the Sonnax firms it even more. :4-dontknow:

That is why I would like to install a pressure gauge to see exactly what is taking place. For now, I just enjoy the feel of a 'performance' shift each and every time. This also does not change if I reboot the system. Personally I really like the consistency of the shifts with the tuner installed, and the extra firm feel with the Sonnax installed. :D

I didn't think the DS had any trans options, only the SC. Do you have a custom tune? I wander if DS does do something with the trans with just the canned tunes that they just don't mention.
Nope. Canned DS 91oct performance tune. I was of the impression that DS did nothing with the trans, but after switching back and forth between stock and the DS 91 canned tune many times, I notice the difference in how it shifts so at this time am quite confident that DS does do something with the trans. I do know that if I dump the DS tune AND remove the Sonnax at the same time, the shifts are so incredibly bad that I could swear the trans was shot. It sorts itself out in very short order, but the first few shifts are pure mush. LOL If I have the trailer in tow when I do this, I get P073X codes which I believe indicate slippage in the trans. I will usually cut the throttle on me when this happens. Usually adapts enough in 3-5 shifts to stop throwing codes, but takes a few acceleration cycles from a stop to fully adapt to where it's completely drivable. If I reboot the system after removal, I do not experience these same symptoms. It's just it's normal smooth car-like shifts.
 
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