Sonnax Electric Line Booster for 545RFE Transmissions

Randy B · **Posted:** Thu Dec 31, 2009 11:36 am

Purchased this from PATC and installed it yesterday. About a ten minute install. Shifts are more firmer and have not had any shutter yet, Cost is about $50.00. Will give more feedback on this in several days.

This family of transmissions uses a full range line pressure sensor mounted on the
outside of the transmission for "closed loop" line pressure control. Due to this
system, traditional methods of raising line pressure by changing the PR spring or
valves have no effect. The Sonnax Line Pressure Booster alters the pressure signal
sent to the computer causing the computer to raise line pressure. Part number
44957-LB1 (68RFE) has 10-15 psi increase, and 44957-LB2 (45/545RFE) has 15-30 psi
increase. Higher line pressure increases clutch holding power and torque
capacity but with these transmissions, the increase has a limited effect on shift
feel. Changes in shift feel will be noticed mostly under aggressive driving or
loaded conditions. This part is ideal for heavy duty and modified vehicles and
even stock transmissions when a little extra pressure is desired. No other
modifications are required. The Line Pressure Booster installs between the
pressure sensor and vehicle harness using OEM style sealed connector

_________________
2005 CRD Limited

linewarbr · **Posted:** Thu Dec 31, 2009 12:20 pm

Got a link?

crawdad-480 · **Joined:** Fri Jan 19, 2007 12:03 pm **Posts:** 47

found this link:

http://www.transmissionsone.com/45rfe_p ... om_pat.htm

Randy B · **Posted:** Thu Dec 31, 2009 1:28 pm

Fuel mileage has increased about 2 mpg. Seems like the rpms are a little higher, at 80 miles per hour rpm was about 2200. So far so good.

linewarbr · **Posted:** Thu Dec 31, 2009 2:05 pm

How can this change the rpm of the engine at 80 mph? Wouldn't that be accomplished through actually changing the gear ratios via taller tires or steeper rear gears?

And if the rpm is higher at 80, then shouldn't fuel mileage go down?

This is not logical, Captain. :ALONE:

Sir Sam · **Posted:** Thu Dec 31, 2009 2:08 pm

linewarbr wrote:

How can this change the rpm of the engine at 80 mph? Wouldn't that be accomplished through actually changing the gear ratios via taller tires or steeper rear gears?

And if the rpm is higher at 80, then shouldn't fuel mileage go down?

This is not logical, Captain. :ALONE:

Ya........I'm with you on that. I'll give him the benefit of the doubt and assume we are not understanding him correctly.

stoutdog · **Posted:** Thu Dec 31, 2009 2:36 pm

linewarbr wrote:

How can this change the rpm of the engine at 80 mph? Wouldn't that be accomplished through actually changing the gear ratios via taller tires or steeper rear gears?

And if the rpm is higher at 80, then shouldn't fuel mileage go down?

This is not logical, Captain. :ALONE:

x2. Considering this was installed yesterday, I'm not sure how he can claim any mpg increase... We all know that the EVIC is inaccurate.

powerstroker67 · **Joined:** Thu Dec 18, 2008 9:21 am **Posts:** 19

I do use these with both in 68RFE and 545RFE trannys and there do raise line pressure as mentioned in the first post. It didn't stop or remove the shudder with the Suncoast t/c and Transgo kit installed in our truck. If you drive trucks with the 545RFE tranny and watch line pressure with a mechanical guage you can see the pressure has been stepped up with either Sonnax plugged in(the values raised are very accurate). The problem is that line rise(or line pressure) starts low and climbs as load and demand increase, this is controlled by the TCM not a hrad part in the tranny. Suncoast has been working on reprogramming on the Hemi 545RFE TCM to go to full line rise just off idle or on tip in. The issue is getting someone inside the CRD TCM to do the same. Ron/Suncoast has also been able to turn a 5 speed 545FE into a 6 speed like the 68RFE, this is just an experiment right now. The efforts that Ron and Suncoast are putting into this 545RFE is awesome and the current version of the Transgo kit should correct the shudder issues. Parts for the pump changed in that Transgo kit approx. 2 months ago

Randy B · **Posted:** Thu Dec 31, 2009 5:30 pm

Yes I agree the EVIC is inaccurate, but there is a increase as per the EVIC. As per the rpm yes it has increased with this mod. Before installing this the rpm was below 2000 at 80 mph. Going down the interstate today at 80 it was 2200 rpm. The transmisson does not go in and out of overdrive like it did before this mod. On hard accelaration it does shift firmer. Yes I just put this in yesterday but have driven over 200 miles. Why the increase in RPM I don't have a clue. But it does not hunt like it did before. Going in and out of overdrive. I will caculate the mpg for a week and see if in fact it increases. But I can say by the seat of my pants I can feel the differance

geordi · **Posted:** Thu Dec 31, 2009 5:43 pm

Very bizarre. From my experience, higher rpm should never equate to higher mileage, quite the opposite. As for hunting or dropping out of lockup (b/c at 80 mph, you wouldn't want it to drop out of the OD gears completely) your CRD shouldn't be doing that at all.

Above 62mph, the tach should never move rapidly in any direction based on changes to the go-pedal. If you press harder (but not flooring it suddenly) the tach and the speedo should rise together, at about the same rate. This is b/c the converter is locked up, there is no slippage of the clutch that would let the engine rpm accelerate faster.

The reverse is true if you take your foot off the pedal completely.

Now in the case of raising the line pressure, that should (in theory anyway) reduce or eliminate any slight clutch slip that could be affecting your torque converter when it is supposed to be locked up, so raising the line pressure could increase the overall MPG. But it shouldn't raise the RPMs, certainly not by 200 or more at such a high road speed. Your converter should be completely locked then.

Perhaps there was something else at work in your transmission?

stoutdog · **Posted:** Thu Dec 31, 2009 7:13 pm

I'm with geordi on this one... there must be something else going on here. Your RPMs shouldn't have changed and you should never be going in and out of O/D at 80mph. Ever. In fact, you shouldn't drop out of O/D until 57/58 mph.

On the EVIC, even an EVIC increase is something to be wary of. If I do an extended highway run, my CRD's indicated mpg will continue to climb throughout the drive.... I've seen as high as 48.5mpg, when I was actually getting more like 33! :dizzy:

RJM · **Posted:** Thu Dec 31, 2009 7:20 pm

If this device works as you claim it does, I would be quite interested! However it does seem to defy the logic of the transmission. ???

ATXKJ · **Posted:** Thu Dec 31, 2009 10:27 pm

Randy B wrote:

Before installing this the rpm was below 2000 at 80 mph. Going down the interstate today at 80 it was 2200 rpm.

?????????????????
80 should be about 2300 rpm - below 2000 rpm should get you around 68?
and in either case it should be locked up so the line pressure shouldn't matter unless the clutches are slipping.
?????????????????

CATCRD · **Posted:** Fri Jan 01, 2010 2:27 pm

Yeah, there is no way you were going 80 at under 2000 rpm. That speed would be more like 2300 rpm.

warp2diesel · **Posted:** Fri Jan 01, 2010 8:33 pm

CATCRD wrote:

Yeah, there is no way you were going 80 at under 2000 rpm. That speed would be more like 2300 rpm.

X2 on that one.

RTStabler51 · **Posted:** Fri Jan 01, 2010 11:06 pm

RJM wrote:

If this device works as you claim it does, I would be quite interested! However it does seem to defy the logic of the transmission. ???

It tweaks the input before getting to the TCM I"m assuming.

DOC4444 · **Posted:** Sat Jan 02, 2010 11:16 am

Regarding the EVIC displaying higher mileage @ higher RPMs:

1. It seems very unlikely any diesel would return higher mileage at higher engine speed, everything else being equal.

2. When I was driving a couple of years ago to a friend's shop to install a Cummins lift pump, I realized I had forgotten to run the tank level down to minimize the weight we were going to have to deal with when we dropped the tank. So, I drove at close to the redline for 45 minutes on the highway to get rid of as much fuel as possible. Much to my suprise, the EVIC displayed significantly higher mileage readings than I had ever observed before under ANY conditions. I wrote it off at the time to some sort of glitch in the system, assuming that could simply not be possible. But, now that I think about it, what about all those people reporting towing in lower than OD fifth lockup and getting better mileage, running higher RPMs than they could?

DOC

FormerlyBankNote4x4 · **Posted:** Sat Jan 02, 2010 11:23 am

Randy,

Did you have shudder prior to install?

linewarbr · **Posted:** Mon Jan 04, 2010 5:37 pm

The only explanation I can think of to answer the rpm difference is that you had low line pressure prior to the mod. Do you still have the pre-F37 TC and pump?

Under no normal circumstance should the trans "unlock" at 80 mph. This behavior would be detrimental to the clutch packs over the life of the transmission, necessitating an early rebuild. If you previously had low pressure, it would be possible for it to hunt like that, since there was not enough line pressure to keep the TC locked up.

Maybe the line pressure resistor "fixed" a problem you didn't realize you had. How's your fluid level?

blake1827 · **Posted:** Mon Jan 04, 2010 6:55 pm

My two cents. It does seem on the EVIC at least to bump mpg in OD at 60 mph @ 1800 rpm and again about 75 mph @ 2200 rpm.
My theory is probably wrong but if someone has a boost pressure gauge installed I'm guessing the turbo is putting out more boost at 2200+ rpms than it does at 2000 rpms. I know the Garrett has VVT but maybe the drag is catching up with the KJ above 75mph.

Sonnax Electric Line Booster for 545RFE Transmissions

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