Sonnax Line Pressure Booster for 545rfe and 66rfe

[thedriver21]

Hey guys, so I was looking around for 66rfe upgrades and was coming up mostly empty until I ran across the Sonnax RFE-LB1 line pressure booster. It’s basically a fooler that tells the computer to give more line pressure. Apparently a shift kit does not really work on the RFE trans and I haven’t gotten custom tuning done yet. So for $80 I figured why not. Install was easy and took about 5 min. All I had to do was bend back the heat shield around the plug, disconnect the old plug, add the fooler in between, and then reconnect. I also disconnected the battery so the trans could do a re-learn. I wasn’t expecting much after install and driving around town i didn’t notice a difference at first. But as a got progressively more aggressive with the throttle I noticed the delay between shifts was shortened and temps were about 5-10 degrees cooler. I only noticed firmer shifts near full throttle but from about 40% throttle and up the shifts become quicker in normal and tow haul mode. For $80 and 5 min I was impressed. Although be warned, in the kit they also include a spring for the trans pump. Apparently with higher mileage trucks it can cause a CEL to appear from over pressure on the sensor. The only fix is to either drop the trans and install the spring, remove the line pressure booster, or do custom trans tuning. Also, this is not to be used for those with trans tuning already done.

[PWJouster]

The quality of the Valve body is our real issue...
low pressure shifts would be ok if the directed pressure didnt divert beyond the proper channels.

i wonder if the higher pressures make the compromised valve body deteriorate further. If it wasnt for that spring, i was also going to do that upgrade.

now ill just have my trans built billet strong once it fully craps out.

[thedriver21]

Ya it seems like the softer metal of the valve body can cause some issues later on in the trans life. From what I could find, the only issues I may run into are the accumulator piston, some of the check balls wearing out, and maybe the pressure regulator valve wearing. It seems like these happen on OE chrysler six speeds regardless of mods done, but it brings to question if the booster will expedite this. My 2013 was running quite a few bolt ons with the 66RFE and a trans tune for the last 50k of the total 100k miles it had on it before the truck was assassinated by a corolla blowing a red light. I luckily never had problems with it like I had with my 47re and 48re in my 97 and 04.

[Colibri]

You can get a billet lower valve body that’s supposed to help with pressure bleeding issues and will tighten up shifts

[PWJouster]

my plan is to build out the entire trans with billet and tune once it finally gives up. It can take power, its just tuned like trash and QC like trash.

im currently experiencing TC lockup issues where it wont lock up from parked into D or R. Takes alot of revs to get moving when cold.

already had valve body replaced and cooling system rebuilt due to prior failure. But at nearly 35k miles, its still under warranty.

[thedriver21]

I wonder if the 66 and 68 rfe valvebodys are the same. Can’t really fine custom 66 valve body’s but 68 and 545 ones are all over the place

[PWJouster]

one of the big dogs in trans jobs was slangin billet bodys and beefness for the lump sum of way too much dough but yo, i need it at $6k EASY.

[PWJouster]

ordered the Sonnax kit anyways. will report back.

[EasyDoesIt]

Looking forward to more feedback on this!

[Colibri]

I wonder if the 66 and 68 rfe valvebodys are the same. Can’t really fine custom 66 valve body’s but 68 and 545 ones are all over the place

Rodeoflyer had his transmission rebuilt with one of these, may want to ask him about it

https://www.dnjcomponents.com/products/d-cf2

[Bigdodge]

I wonder if the 66 and 68 rfe valvebodys are the same. Can’t really fine custom 66 valve body’s but 68 and 545 ones are all over the place

They are not the same

Sent from my Pixel 4 XL using Tapatalk

[PWJouster]

Holy Crap.

i think my shifts were so "off" that i can immediately tell that the shifts have less hesitation, hang time, and no lurching.

cant promise that it wont grenade the trans eventually...but it does what it says it will do. And it did so for me nearly immediately?!

Its more noticeable when the truck is shifting up or down with a heavier throttle modulation and higher rpms. Almost like it has Tow/Haul mode shift pressure but not the engine breaking high revving nature of it.

Why do we know of only 1 or 2 people who have built up a 66rfe...

[ramv]

Those with the Sonnex happy? I assume with 66RFE, if you do a custom engine tune (Hemifever) that doesn't do anything for the transmission tuning? It appears on his sight he has tuning for the 8 speed but nothing for the six speed is listed.

[ScubaSteve]

Those with the Sonnex happy? I assume with 66RFE, if you do a custom engine tune (Hemifever) that doesn't do anything for the transmission tuning? It appears on his sight he has tuning for the 8 speed but nothing for the six speed is listed.

I am on the hunt for some transmission upgrades due to a shudder/hesitation with downshifting from 3rd to 2nd under throttle, and the issue seems to be a bit more exaggerated since I had my truck tuned.

That said, in my correspondence with Sean (Hemifever), I understand that he does not do anything with regards to the transmission tuning aside from the adjustment of shift points as well as the reduction of torque management. To me that says that line pressures and the such remain the same and mechanically everything functions the same in terms of solenoids and pressures, as stock.

I would assume that he is capable of doing more however, I did not press that far, as my concerns appear to be due to some sort of defect in the trans.

[ramv]

Gotcha, no that makes sense. Currently I'm not having any issues other than an occasional weirdness on transition between no throttle and part throttle but seems more programming related, as its at low speeds and no load.

[PWJouster]

i did this kit but did not install the spring...

it helped for a few weeks, but eventually i was still unhappy with the trans behavior. Maybe the full install would be better, but an aftermarket trans build is the only way to beat the factory tuning and crappy casting.

[ramv]

Sonnex kit helped firm up shifts but 6-5th downshifts were rough. Transmission finally gave up. Billet replacement going in now

[RustyPW]

Sonnex kit helped firm up shifts but 6-5th downshifts were rough. Transmission finally gave up. Billet replacement going in now

[ramv]

I do have Sonnex line booster for sale now if anyone is interested.