RPM Curiousity

[wingot]

Ok, I have been noticing this for a while, since I changed my transmissions vacuum control modulator(it was leaking) in my '91 explorer the rpms have changed. Previously it would cruise around 1600 rpm at 55, and 2000 at 65, but since ive changed it the rpms have been kind of varied at 55, and where from 1700-2200, and 65 is usally around 2400-2600. I was just wondering what could be causeing these changes. I think it may be that becase no transmission fluid is beign sucked into the engine that maybe it needs to have higher RPM? I dont know, and I dont think anything is wrong with the tranny, im just being curious.

 

[MrShorty]

Educated guess: sounds almost like you may have nicked a wire or something so that the torque converter lockup clutch is no longer engaging. 1st thing I'd suggest is to make sure all the "shifts" are there (1-2, 2-3, 3-lockup in D, 3-4 in OD, 4-lockup in OD).

 

[IAmTodd]

I'd think that the OD light would be flashing if it weren't funcitoning. But it seems the TC isn't locking up.

 

[wingot]

well once it gets up to speed the rpms stay at w/e they are at, usually 1900-2000, but i was just wondering why i get this variation... shouldnt it always be the same RPM for the same speed? It shifts fine, all the gears shift, and od usually kicks in around 45-50 mph.

 

[metstalker]

I'd think that the OD light would be flashing if it weren't funcitoning. But it seems the TC isn't locking up.

i dont think we have OD lights on the first generation do we?

 

[EMG7895]

Nope no od light

 

[Longjohn119]

What you are seeing is the torque converter locking and unlocking ... if you start giving it more gas, say going up a hill, the torque converter unlocks and you'll see an RPM increase, when the load drops it locks back up again ... whether yours is unlocking too easily I couldn't say but I'd definitely double check the fluid level

 

[Nuggethead 420]

So that does not answer the question. What is the main problem the TC lockup solinoid, The 3-4 shift solinoid? I am having the exact same issue with my 91.
I am at about 3000 RPM at 65. The 3-4 shift solinoid is the most likely problem but no way to test without taking off the pan and check it. I was also told to check the screen for the 3-4 if there is one there to make sure it is not plugged.
This seems to getting more common and more of a concern as gas prices rise.