Mileage reduced after Suncoast??

greiswig · **Posted:** Tue Nov 11, 2008 11:56 pm

Hi, all,

I know it's a small sample size. And I know EVIC is imprecise, but I don't have another highly accurate way of measuring the fuel consumption. Hopefully time will tell a different story than the one I've been told the last few days.

5000 miles after the "recall" to replace the torque converter, the new OEM converter started shuddering under load when the tranny was locked up. The TransGo shift kit did nothing to remedy the problem. So I forked out for a Suncoast.

The shudder is gone, as far as I can tell. But I have a 10 mile section of highway I travel daily, and I am able to reset my EVIC at the start of that section, and see between 26.5 and 27.5 MPG at the end. Reliably. Now, a hundred miles or so after the Suncoast was installed, the two trips I've had on that same stretch of highway that reported under 25MPG.

I expect some error, but I expected there to have been an increase in mileage. Any ideas why I might be seeing what I'm seeing? Odd coincidence?

kdlewis1975 · **Posted:** Wed Nov 12, 2008 12:26 am

...time of year? Are they using the winter blend of diesel in your part of the country? That sometimes results in ~10% fewer mpg.

greiswig · **Posted:** Wed Nov 12, 2008 12:50 am

kdlewis1975 wrote:

...time of year? Are they using the winter blend of diesel in your part of the country? That sometimes results in ~10% fewer mpg.

Negative...my fuel is very consistent do to its source, which is not a major petro company. Good guess, though.

I should add that the install was done by a shop, not by me. I'll have to ask them if they tinkered with anything else...

kdlewis1975 · **Posted:** Wed Nov 12, 2008 2:02 am

...just a suggestion. I generally see a slight dive in mpg here in MI due to temperature and the winterized fuel.

Did they put ATF+4 back in it? Other than the possibility they may not have assembled it correctly, it's hard to know. People generally report getting the same or better at least. I wouldn't think there would be a "break-in" period involved that would matter. Go figure.

Uffe · **Posted:** Wed Nov 12, 2008 2:38 am

I don't see how the converter would make any difference on the highway, it would be locked up anyhow. I guess it could splash some more ATF around but does that sound reasonable?

I think it's because of wind conditions have changed, or because of a drop in temperature...or simply your foot being applied more fiercely

fastRob · **Posted:** Wed Nov 12, 2008 8:59 am

Have you checked the fluid level?
Other than the wrong kind of fluid what else could have been done?
I have not noticed much change in mileage with the Suncoast.

Joe Romas · **Posted:** Wed Nov 12, 2008 10:59 am

Another guess :wink:

Has the battery been disconnected so the TCM has to relearn?

greiswig · **Posted:** Wed Nov 12, 2008 12:26 pm

Thank you all for the ideas. I really do appreciate them.

The battery disconnect was one thing I had considered, too. Pretty clearly they had done something, since the radio station was at 530AM (or whatever it is right after you have reset everything). But I guess I would expect that both the ECM and TCM would relearn things within 100 miles or so, or a few start/stop cycles. I'm hoping that this is the explanation.

I will ask them about what kind of fluid they used. I'll also double check the level, but they drove it around quite a bit after the install, since they "thought they still felt a shudder." They then got it back to the shop and checked the fluid level again, and it was good when I got it.

I forgot to mention, but my foot isn't in it any more than normal on these test sections of highway, unless the cruise control parameters have suddenly changed. ;-)

The weather HAS changed, but not drastically: I live in PDX, and recently we've had a good deal of rain, but it is not greatly colder than it was before.

Thanks again,

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

I'm in PDX as well, running B20 from Jubitz religiously. I've noticed no change in my mpg. What transmission shop did you use?

greiswig · **Posted:** Wed Nov 12, 2008 3:08 pm

Threeweight wrote:

I'm in PDX as well, running B20 from Jubitz religiously. I've noticed no change in my mpg. What transmission shop did you use?

TransAction Transmission in Forest Grove, where I live. They have a good reputation, and after speaking to the mechanic beforehand about issues, I found him quite knowledgeable, even about this particular tranny.

onthehunt · **Posted:** Wed Nov 12, 2008 4:14 pm

Does the Suncoast converter weigh more than the stocker?

ATXKJ · **Posted:** Wed Nov 12, 2008 5:20 pm

The Suncoast does weigh more (I didn't measure just remember picking it up) but nowhere near enough to impact mileage.

and as Uffe pointed out - on the highway - the Torque converter should be locked - which means it should be out of the mileage calculation completely.

However 2x check the fluid type - I know a couple of folks have had the wrong fluid put in - that might affect clutch friction which could affect mileage.

clday25 · **Posted:** Wed Nov 12, 2008 9:36 pm

Well, I changed to many variables when I did the Suncoast Mod last year to weigh-in on the mileage issue. But I can say that the change in temperature here in the NW has had a small (1-2 mpg) effect on my mileage.

Don’t get down on your mileage too much, you’re doing better then me, I’ve been hand-calculated my mileage, tweaked for tire size, and only hit 21.5 - 24.5 since my InMotion II, TransGo, Suncoast and Lift Pump mods…. It’s those dang 265’s I tell ya.

On a side note, the U-joint comment is probably something I should follow up on. I still get a vibration at times when I accelerate hard, really hard, while in O/D. Thanks for the info Bob ;-)

greiswig · **Posted:** Wed Nov 12, 2008 9:45 pm

This came to me via email from Bob, who was having trouble posting. The content makes it well worth making sure it gets posted successfully:

Bob wrote:

Hi George,
I tried to reply on LOST, but it keeps requiring a new login after responding - problem is, the original text is gone on each new login.

Yes,

Disconnecting the battery while pulling the transmission (which should definitely be done) will affect your mileage. I have noticed that mine will fine tune for several months after a disconnect, and this summer after a prolonged battery removal, during which time I replaced a front axle cv boot, both front ball-joints, struts, diff oil change, and U-Joints, the mileage and power level were down for 2 or 3 weeks. I noticed the difference immediately. I suspect we're so familiar with our Jeeps by now that any change is detected very quickly.

I was quite surprised, but it relearned and went back to about 80% in about 2 weeks, but took at least 3 weeks to get back to full mileage. I also had to do some Interstate driving before it really dialed in. I have no idea why. One question is did you have the pump replaced or was that already done? Is the shift quality correct? One immediate difference I noticed was the reduction in power train vibration once the SunCoast was installed. Perhaps my replacement TC was much worse than average, but even my wife noticed the difference.

I'd check the tranny fluid level for sure, but give it a couple of weeks to relearn and dial in the TCM. Alternatively, you could find a good steep mountain and give it a rigorous pedal to the medal workout and see if that helps the TCM dial in faster. Even if it doesn't, it might give you a chance to see how the Suncoast works on hilly terrain. Another early wear item I found was the U-Joints. Those crap stock joints went out at 37K and were causing a strong vibration under hard acceleration.
I replaced them with some greasable ones and the driveline is very smooth.

I don't feel like debating it on the forum, as I notice all but one responder don't have a SunCoast installed - doesn't seem like they would have a common background to offer advice from.

PS - mine is running better than ever at nearly 40K miles and I've forgotten all about any tranny shudder. The lift pump, segr and SunCoast really gave the little Jeep a new feel. I would highly recommend a front and rear diff oil change with a high quality oil.
When I did mine at 38K miles, the amount of very fine metallic particles in both was surprising. After reading about your experiences on your Alaskan adventure, I'm convinced you can change your own diff oil!

I went with Amsoil 75W-140 with amsoil trak-lock additive and I'm surprised at the smoothness. I'm not an Amsoil freak but I am very happy with how quiet the rear end is now. It had developed a distinct whine at 65 mph before and since the change, it's gone. I used a can of brake cleaner to totally clean out the rear diff and used a pump to put the new fluid back in. This is an hour job if you take your time for the rear. Front diff is easier as there is a drain plug as well as a fill plug. Rear diff requires pulling the back plate, but it's easy.
Red silicon diff seal from a parts house worked fine on mine. No leaks at all. Save yourself some money and take your wife to dinner with the savings. Be sure to buy a pump for the oil - it makes it a 2 minute fill job.

Regards,

Bob

Mileage reduced after Suncoast??

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