So my '88 f250 w/ 460 is having a hard time shifting into third gear. It shifts from first to second just fine, but when going from second to third, it will not shift unless i decelerate to 200-2500 rpm's and then accelerate again? I have no idea what the issue could be and am hoping that someone here might be able to point me in the right direct.

Any help would be greatly appreciated,
Steve

 

It would be a big help if you could give us just a little hint as to what transmission you are talking about...,.,,

 

It must be a C6. I have the same year model and engine.

It sounds like it is wanting to stay in second longer than you want it to. Have you changed the gears or tire size from stock?

I had a chevrolet that wouldn't shift correctly after I installed larger tires and the lift kit. It was always searching for the right gear and bugged the hell out of me until I put 4.56's in diff's.

 

" If " it is a C6, the first thing I would do is check for vacuum at the modulator (right rear of trans), and for defective modulator (trans fluid in vacuum line).

 

Thanks for the info guys. Im not really sure exactly what tranny im rolling with, so I will have to identify it and post that up.

Steve

 

So i had a chance to look into what tranny my truck has, and it is in fact the c6. I am going to start with the vacuum at the modulator as suggested. is there anything else it could be and that i should take a look at while i am at it?

Thanks,
Steve

 

Hmmm I would have figured it would be a E4OD. In that case yes get a modulator but you might as well get an adjustable one. Not much more money and makes it easy to tune.

 

So I had a chance to replace the modulator this weekend and was really hoping that it would resolve the issue... but it seems that would be too easy!

Although the truck shifts much smoother, it is still not shifting from 3rd to 4th unless I decelerate to 2000 rpm and then accelerate again.

Any body have any other ideas?

Thanks ya'll.

 

Wait a minute!!! If it's a C6 there ain't no 4th.. A C6 is a 3 speed automatic..

 

Did that modulator look something like this?

 

Sorry bout that, i misspoke. The problem is when its shifting from 2nd to 3rd.

Yes, the modulator looked just like that??

 

Ok,, you had me confused for a minute..

About the only thing I can think of at the moment is either something is stuck/broken in the valve body, or maybe the intermediate band is worn out or way out of adjustment...

I had a C6 one time that had an intermediate band strut fall out and land in the pan... It got me home (about 350 miles), it would work fine in first, but if you let it shift to second it was like going to neutral, but you could go in first and rev the engine to the point you were going fast enough for it to go into 3rd, and like yours when you let off it went right into 3rd and gave no problems until you slowed down to the point the trans needed to down shift, then you did it all again!!!!

Does it seem like you are slipping in second?? If so it may be time for a rebuild.

If you would like to try/or read about adjusting the intermediate band, here is a thread on it.... https://www.ford-trucks.com/forums/1...rake-band.html and

 

Thanks for the info, sound like mine is having that same issue. I am going to give this a try and hope that it works.

I talked to the friend that gave me the truck and he was surprised that i am having issues, because he had the trans. completely rebuilt about three years ago?

Could old fluid and filter be that cause at all?

Thanks,

 

Is the fluid clear and red? If it's black and smells like it is burnt then you have bigger problems than dirty fluid.. Also, with the filter, a C6 uses a fine screen for a filter, if it has enough junk in there to plug up the screen, again you have bigger problems than a clogged screen.

I'm not saying the fluid and filter don't need changing, it very well may.. You can tell by the color of the fluid... I am just saying the fluid is not really what is causing your current problem, cruddy fluid could have clogged some ports in the valve body and could be causing it, but there again for this to happen the fluid would have to be contaminated with clutch material/metal from worn parts..

 

Yeah, the fluid is pretty dark and appears to be burnt? What issues am i looking at if this is the case?

I'm starting to get bummed!