Shifting Problem While Towing

[CarFreak146]

Truck :: 94 4wd, 32" tires, 3.27 gears.

Problem:: While Towing tonight, my AUTO would not shift outta first gear, unless I let of the gas and let it idle back down to about 25oo rpm.... it was wierd.... anybody possibly know what was wrong?

--Ryan

 

[Brain]

Must have been towing more than a motorcycle...don't worry, it is normal for the tranny to stay in lower gears when towing. Check out this portion of an article:

"The governor assembly, located on or driven by the transmission's output shaft, senses road speed and sends a fluid pressure signal to the valve body to either upshift or downshift. When vehicle speed is increased, the pressure developed by the governor is directed to the shift valve. As the speed (and therefore the pressure) increases, the spring tension on the shift valve is overcome and the valve moves. This action causes an upshift. Likewise, a decrease in speed will result in a decrease in pressure and a downshift.

Although the governor sends a signal that will force an upshift, engine load may cause a delay in the shift. This allows for operation in a lower gear when there is a heavy load and the vehicle needs the gear reduction. During heavy load operation, the governor pressure must be strong enough to overcome the high throttle pressure plus the spring tension on the shift valve before it can force an upshift. Because of this, the transmission will remain in a particular gear range until a higher-than-normal engine speed is reached."

I think that last part kind of describes what you were experiencing. See if the problem remains when you aren't towing.

 

[CarFreak146]

well, I understand that part of it, but why is it still doin that when I'm not towing?? I don't have anything behind my explorer anymore, and its still doin it.... I checked my fluid, and it was low, so I topped it off... no change.... I"m stumped.

--Ryan

 

[audiodude332001]

what type of trailer were you towing? How heavy was it?

 

[Mbrooks420]

You couldn't be shifting from 1st to 3rd could you? I lost second gear once and it sounded similar to what you are experiancing. I'd have to rev the motor out, and let off the gas until it clunked into 3rd.

 

[CarFreak146]

I was towing an older stock car trailer

You couldn't be shifting from 1st to 3rd could you? I lost second gear once and it sounded similar to what you are experiancing. I'd have to rev the motor out, and let off the gas until it clunked into 3rd.

I don't think so.... becuase, if I would come to a complete stop, then put the tranny into 2nd (using the shifter) it would clunk into 2nd and it'd work, but say while I was driving and I did that same thing (dropped it into 2nd) it was like neutral, not engaging, and just revving.

--Ryan

 

[Mbrooks420]

A trip to the tranny shop is probably going to be in order. How low was the fluid? What color?

 

[CarFreak146]

the fluid was LOW... but it was still red.

 

[Mbrooks420]

You must have puked a bunch out then. I'd never tow that trailer again, it's apperantly too heavy.

 

[CarFreak146]

well, when you looked at my tire/gear combination, a Geo is too heavy for my vehicle, but its the only thing I have to tow with... well, I've got my Oldsmobile Intrigue, but that would be just wrong.

--Ryan

 

[Mbrooks420]

Not if your going to smoke you trans every time you tow with it. Next time rent a Ranger for the day.

 

[CarFreak146]

or I'll just borrow my dad's truck or something...

so takin it to a tranny shop would probably be my best bet then huh?

 

[Mbrooks420]

That would probably be my next move. I'm mechanically inclined, but transmissions make me nervous. I'd ask around and see if there is one that someone you know has dealt with. Tranny shops vary in service, and price greatly. There are also a lot of tranny shops that will just rip you off.

 

[CarFreak146]

yeah, I know that's true.... I was hoping that one of our A4LD geniouses would see this thread.... I know there's a couple guys that have rebuilt them and know a LOT about them.... I think Brian was one of them, can't remember the other one.

--Ryan

 

[Mbrooks420]

Glacier and Operahouse are the other 2 tranny masters, that I know of. It's possible that something major isn't wrong, and only requires a pan dropping.

 

[Brain]

Apologies for taking so long to respond, but I got tied up this weekend with family that came to visit and a friend in the hospital. So now I think I understand the symptoms (wasn't completely clear before):
1) when in OD shifter position, it doesn't upshift from 1st to 2nd unless you get off the gas
2) when in D and downshifted into 2nd (manual), it would over-rev and not engage
3) when shifted into 2nd (manual) from a stop, it would engage

These symptoms mean that you do have 1st, 2nd, etc., but they just aren't shifting at the right time. There are two things that immediately come to mind. The vacuum modulator and the govenor. The good news is that both of these can be checked/fixed without removing the tranny or even dropping the pan.

 

[CarFreak146]

Hey Brain, thanks for the info, I dunno if it matters or not, but for #1, it's in the Drive position, no OD.

How would i go about checkin the vacuum mod. and the governor?? is it something that I can check and replace myself?

--Ryan

 

[Brain]

After thinking about it some more, I think it is probably the govenor. Here's Glacier991's A4LD rebuild diary's section on the govenor:
http://www.explorerforum.com/forums/showthread.php?t=101571&highlight=A4LD+DIary

The first part, and a look at the govenor from the rear, is here (look at the bottom of the page at the bottom of post #57 of the thread):
http://www.explorerforum.com/forums/showthread.php?t=98027&page=3&pp=20

If you need more pictures or advise, let me know and I'll do what I can.

One problem with just cleaning the govenor is that it will get dirty again over time (maybe 20K, maybe 100K miles) unless the offending contaminants are eliminated, and I think one of the biggest offenders is the rear sprag caps and the washer behind the rear race. That is pretty well documented in the A4LD diary and the Frankentranny thread if you are curious about what's the cause and not the symptom.

As for the vacuum modulator, it is on the passenger side of the transmission, really close to the catalytic converter (directly behind the two round servo covers). There is lots of good info on this site about the vacuum modulator (where it is, how to get to it, etc.). Just do a search or read the A4LD rebuild diary.

BTW, the modulator only costs maybe $20, and the govenor is $60 (but it usually doesn't need to be replaced, just cleaned so the valve inside the assembly doesn't stick and keep the upshift into 2nd from happening).