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-   -   Overdrive & engine rpm question (http://www.jeepgarage.org/f5/overdrive-and-engine-rpm-question-20010.html)

402 Motoring 03-09-2011 03:54 PM

Overdrive & engine rpm question
 
So I just picked up an 05 5.7 Limited with 110K the other day and looks like I may already be experiencing some transmission issues. I mostly do hi way driving and I notice that at 65 mph my engine rpms are up in the 2K range. This seems a little high to me. To the guys with this same setup what are your rpms showing?

Thanks in advance.

robpp 03-09-2011 04:05 PM

Re: Overdrive & engine rpm question
 
i have the same trans and rear. Iwant to say at 75-80 i am just over 2k rpms.

545RFE, AUTOMATIC MULTI-SPEED
Three planetary gear sets, one overrunning clutch, with Electronic Range Select (ERS) driver interactive control, electronically controlled torque converter clutch.
Gear ratios:
1st - 3.00
2nd - 1.67 (upshift), 1.50 (kickdown)
3rd - 1.0
4th - 0.75
5th - 0.67
Rev - 3.0


Axle: - 3.73

Final Drive Ratio: 3.73 with 4.7-liter or 5.7-liter engine

Overall Top Gear: 2.50 with 3.73 axle

402 Motoring 03-09-2011 04:08 PM

Re: Overdrive & engine rpm question
 
Yes and it has the Quadra Drive II transmission.

robpp 03-09-2011 04:24 PM

Re: Overdrive & engine rpm question
 
Quadra Drive is the 4wd system. it is the top of the line 4wd system, there are 3 of them. you have Electronic Limited Slip diffs.

545re something or other is the trans.



you can get more info about the wk than you ever need at www.wkjeeps.com

jeepgcoman 03-09-2011 06:12 PM

Re: Overdrive & engine rpm question
 
In the 63-65 mph range you're right near the stock shiftpoint from 4th to 5th, and both are overdrive gears. With stock size tires, if you're in 4th, you'll be ~2200 RPM, and 5th you'll be ~1900 RPM. For me, living in hilly terrain, it's just about perfect if I drive at 63-64 mph. On level ground I goose it a little and it shifts to 5th. On inclines I backshift it to 4th and then back to Drive. This allows maximum use of the MDS, as many times on slight inclines the MDS will be off if in 5th, but will come on if in 4th (Drive). Also, be aware that with MDS active it will add ~50-125 RPM. When it comes out of MDS the engine RPM drops the same ~50-125 RPM to match turbine speed, if locked. The converter lock also plays a part here. It is not on when in MDS mode, but will come on, sometimes simultaneously, when the MDS kicks off. Bottom line, in this speed range, you should notice quite a bit of RPM shifts (could be mistaken for "hunting"), depending on the amount of hilly terrain, wind, etc., and yes, even type of road surface. I've seen up to about 4% change in engine load when changing from one type of road surface to another....i.e asphalt to concrete, or vice versa. This will also affect the MDS, which is load sensitive, among other parameters.


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