I also experimented with a seal on the bottom of the bed next to the cab, in all positions (short seals on ends or in middle) or all the way across, it added drag. It did add stability to the back of the truck. That coupled with a behind the front grille block in the upper half of the upper portion of the grill, made for a very stable some pretty crappy conditions... aka high winds on a bridge I cross daily. The first thing I noticed when I pulled both off (grill & lower horizontal bed seal) was the loss of the stability gained by both seals... it was nice.

 

here is a link to my trucks 11 yr makeover I did years back, there may be some other things in there you can leverage...

(1) 11 years, 345k on the clock, time for a makeover... | Cummins Diesel Forum (cumminsforum.com)

and the aero effort...

(1) MPG improvements through aero mods | Cummins Diesel Forum (cumminsforum.com)

 

You have certainly been giving this a lot of thought and experimentation. I look forward to getting time to study this later.

 

I want the most out of both trucks... and yeah I might have had too much time on my hands lol

 

I have the flex-a-lite Efan in my 05 and have had it for about 5 years going now. By far one of the best upgrade I have done. Yes the temp swings are noticeable on the gauge but if you read them from the ODB port they are not. It did help a little on the gas mileage and power but I wasn’t really looking for that. I was more going for the cooling of the engine results since I live in S.E.Texas. Temps here have been 100-108 this summer and my gauge hasn’t gone over the 1/2 mark at all even in traffic. I don’t do any heavy hauling or stuff like that alot but when I do I can tell the difference with this. I highly recommend it.

 

Great, I appreciate your Yea vote 'FOR'
Thank you... \

I am still looking to find a lost $350 dollar bill lying on the sidewalk and I'll get hooked up and post my review of the system.
Esteemed member Mangoon suggested that many reviews on here over the years but I am not finding many within my search criteria. Nor even a lot on Google or Bing for that matter other than Flex-A-lite website and as you can guess, they are positive salespitch.

I am not hauling much, heavy, or far... but I will retain the original components (clutch fan and shroud) incase my mission profile should change, I could restore it if needed.

 

OK, three months later and I broke off a Black Friday deal at JEGGS and bought the Flex-A-Lite eFan kit. It arrived today.
I will retain all my factory shroud and clutch fan in case I choos to revert back to factory parts

More coming soon, Same BAT channel. Same BAT time. dunna dunna dunna dunn dada BAT MAN!

 

is that a single fan?

 

Yes, single fan on the Flex-A-Lite 183

Easy install
Have yet to evaluate if I can determine increase in mileage (both the overhead computer calculation AND / OR doing the full tank math)

*** BONE TO PICK WITH Flex-A-Lite and the distributor JEGGS out of Ohio (online jeggs.***)
When installed, everything went smooth BUT there was a big vibration issue and especially noticeable when the fan runs after shut down. LOUD GROANing noise, thought that we were parked next to a running locomotive.

I called spoke to Flex -A- Lite and they thought that thought unlikely, perhaps the blade was out of balance. "Get with Jeggs and they'll arrange to replace it..."
**SO after 53 minutes on hold, I get a guy who SELLS me a new blade and then I have to return the old blade for refund... OK,
The blade arrives and right away I see that there is a little metal clip on the new blade (weight) like balancing a car tire or ceiling fan.
I easily swap the blade and sure enough this new one with the balancing clip runs much smoother. (less vibration and noise)
*** Now what chaps my **** is that I am on the hook for paying $20 return shipping to get my $50 refund AND the time to carry this thing somewhere to have it sent back like the UPS STORE..
For me, as a consumer, I DO NOT ENDORSE Flex-A-Lite Or Jeggs for their F U business practice and customer satisfaction
Flex A lite should have just sent me a good replacement fan blade

 

I am visiting with you today to report on my Flex-A-Lite radiator cooling fan ' ' upgrade ' '

I bought the kit on sale at the end of 2023 (package arrived first week in December and I finally got around to installing it in mid to late summer August/September 2024.
So I have had it installed for just over a year, and I am satisfied with it.

I took the truck on a distance 'hyper drive' from Jupiter, FL to ST Augustine ( about 250 miles each way ) and [63 MPH seems to be a sweet spot for me] I set the cruise control, get in the right lane, and let all the other aircraft have a dog fight around me (the bomber) I just keep trucking to deploy my payload...

I am satisfied that installing the e-fan was a good thing. Watching the economy computer, reset once on the highway and set up in 'cruise configuration' is it possible that I remember a long term, stabilized number of 18.6 mpg??? Surely I took a picture but I am at a loss to confirm that. I had averaged 12 ish mpg. and perhaps 14 on longer cruise runs. I have the full tank to full tank mileage written on my saved receipt, somewhere.

I'd venture to guess at least a 2 mpg average fuel economy boost...
And all South Florida 2025 summer, trailer hauling trips included, never once to I feel that the cooling system was not performing.
and of course YMMV
Cheers

As previously told, my original Flex=A=Lite had an out of balance fan blade when I first installed it. A [warranty] replacement blade smoothed that out, BUT IT COST ME $20 (+ time) S&H to get my $50 wobble blade refund (***-hats suck)
E-FAN good
Flex-A-Lite / JEGS --- NOT SO GOOD business practices (for a consumer)