help - occasional highway RPMS surge to 4200 but Speed only 60?

[ELeBlanc]

Hi all. Thanks for all the help you provide. Highway driving in one of my two 97 Explorer 5.0 AWD. Issue is with 77k truck.

Normally the vehicle is around 2100-2200 rpms when driving in the 70-73mph range.

A couple of times on long highway trips, after pulling onto highway after rest stop, the RPMs go up to 4200 but speed tops out at 60. What I have done, while still on the highway, is shift the car into neutral and then back into drive and this seems to correct the issue.

Also should mention I do frequent 600 miles weekend drives and this has happened three times so its not all the time.

Any thoughts?

thanks,
Einar

 

[CDW6212R]

The trans needs some attention. Most issues that kill a transmission, are serviceable parts, not the main rebuild parts.

Start with a fluid and filter change, including draining the gallon of ATF in the torque convertor. Get a look at the pan and material left in the old fluid. Most likely it will need other things, and almost all repair shops do few of those in a rebuild, and don't want to touch one to "fix it." They want to do the whole thing, the rebuild which is a day's work.

If you dig around forums like this with vehicles that use the 4R70W, you can discover how many parts are possible to replace by anyone familiar with automatics. Almost all of the parts I'd suggest are included in a full rebuild, the biggest cost part that is. I like Sonnax parts, so I'd include items which shops don't mess with unless pushed to etc.

 

[boominXplorer]

You might be shifting into 2nd instead of Drive

 

[gmanpaint]

Sounds more like a Range sensor or possibly the vss is going bad. Look these up for failures, and see if the symptoms match your issues.

 

[1998Exp]

And no CEL? I would scan for transmission-related codes anyway.

 

[ELeBlanc]

And no CEL? I would scan for transmission-related codes anyway.

Would not tranmission related codes show up as CEL using OBD 2 scanner? Been thinking about buying one of the cheap scanners

 

[1998Exp]

Would not tranmission related codes show up as CEL using OBD 2 scanner? Been thinking about buying one of the cheap scanners

A code needs to be set several times in order to set the CEL. Until then it's "pending". A decent scanner will show pending codes.

 

[CDW6212R]

You might be shifting into 2nd instead of Drive

with that rpm, it may well be in a different gear. Check the gear shift mechanism, is it loose at all, and does the dash indicator match each selected gear closely? Those can be separately off and cause issues.

 

[96eb96]

You want forscan to monitor transmission parameters while driving. Many cheap OBD adapters work, BAFX is one, or search for Forscan adapter. Download FORScan
You will see the computer commanding gear changes, lockup status, the sensed position on the sensor, etc. A code may not be set if it happens quickly or infrequently. You can even set it up to log over an entire trip. It is no different than how Ford would troubleshoot a brand new Explorer with a trans issue.

 

[96eb96]

Also, 97 4R70W must haves:
**MUST** Replace 1-2 Accumulator and springs with revised version. This could keep you from shifting and cause the flare. Optionally replace 2-3 (but you have to drop the valve body)
Total fluid replacement with Mercon 5 if you are not sure.

http://ww2.justanswer.com/uploads/bobover/2010-01-23_223409_1997F1501-2SHIFT.pdf

In the late 90s I actually worked for a while in a shop in bklyn that serviced taxis/crown vics/TCs(same exact trans) saw these issues frequently.

 

[Winter Hawk]

I'm having somewhat the same issue with my '89 Ranger, 2.9 engine, 5 speed manual tranny, 178k miles. The other day I downshifted to coming into a stop light and the tach pegged out, even though I was probably around 3500 rppm. It dropped back down to normal but then started oscillating between 2000 rpm (normal for 55 mph in 5th gear) and pegged. It seems to have settled down again, but this has happened before. Would it be a problem with the tach itself, or with a sensor?