Throttle Valve Cable

[MarkEagleUSA]

What would the symptoms of a disconnected TV cable be? This morning while attempting to adjust it on my 03 QC I found it was disconnected at the transmission (and looks like it has been for a while). The 47RE has shifted strange when cold since I got the truck in March but seemed fine after warming up.

This weekend with the temps above 90 I was running the A/C and couldn't get the transmission to kick down for acceleration so I decided to do the adjustment. After reconnecting the cable the shifts are now much better (smother and more precise) and the kick-down works like it's supposed to.

Just a little curious as to why the cable was disconnected. Is there any reason to have it that way?

 

[cerberusiam]

Every clutch pack in the transmission is now suspect for wear and damage. The TV cable adjust the apply pressure in the clutch packs to compensate for load. Applying clutch packs under load is a good way to burn them up quickly.

 

[MarkEagleUSA]

Every clutch pack in the transmission is now suspect for wear and damage.

Not what I wanted to hear...

I guess I'll keep a close eye on things to make sure nothing is drastically wrong.

 

[cerberusiam]

I would do a fluid exchange and check the pan for detritus. If you drive it easy with it disconnected you might be fine, pan should indicate if excessive clutch wear has happened. On the flip side, about 10 passes down the drag strip toasted every clutch pack in a built 727 when someone forgot to tie the TV lever open or mod the VB.

 

[MarkEagleUSA]

I would do a fluid exchange and check the pan for detritus. If you drive it easy with it disconnected you might be fine, pan should indicate if excessive clutch wear has happened.

I guess I'll be changing the fluid soon. As for driving easy, I haven't done anything extraordinary since I picked her up in March. The problem is I have no idea how long the TVC has been disconnected. I will say the truck shifts a lot crisper now that it's reconnected.

 

[sag2]

Every clutch pack in the transmission is now suspect for wear and damage. The TV cable adjust the apply pressure in the clutch packs to compensate for load. Applying clutch packs under load is a good way to burn them up quickly.

This is not correct. Line pressure is the only pressure that applies a clutch in an RE transmission. The throttle pressure is used to overcome governor pressure to make the shift later with more throttle. If TP is higher than GP the shift is later, if GP is higher than TP the shift is sooner. The TP/GP is what moves the shift valve, the shift valve then directs line pressure to the clutch. Looking at any circuit diagram will show this to be true.

 

[MarkEagleUSA]

This is not correct. Line pressure is the only pressure that applies a clutch in an RE transmission. The throttle pressure is used to overcome governor pressure to make the shift later with more throttle. If TP is higher than GP the shift is later, if GP is higher than TP the shift is sooner. The TP/GP is what moves the shift valve, the shift valve then directs line pressure to the clutch. Looking at any circuit diagram will show this to be true.

Does this mean that having the TV cable disconnected won't necessarily cause any damage? Everything seems to be ok since reconnecting the cable earlier this week. In fact, the transmission seems much more responsive (i.e. shift points are much closer to what I think they should be). I just don't want this thing to grenade on me.

 

[sag2]

It should not have caused any damage.

 

[cerberusiam]

The diagram is mislabeled as far as the pressures we normally talk about. Line pressure is actually apply pressure, not straight line pressure which is not variable. As indicated the "line" pressure is variable and that is controlled by the throttle valve position. The diagram represents gov pressure as throttle pressure, it is just a nomenclature difference.

Bottom line is full pressure is not applied to the clutch packs unless throttle valve is at maximum travel and there will always be some bleed off due to built in leaks and pressure control. In reality minimum apply pressure is usually somewhere around 70 psi on a good trans, lower with wear, with the throttle valve at minimum.

 

[sag2]

I found another larger diagram you can actually read from an old Torqueflight and you are correct, the TP does act on the regulator valve to alter line pressure to the clutches. Although it would be good to have more apply pressure (holding pressure can be much lower. The VLP electronic transmissions drastically reduce LP once the shift is made.) unless he was towing or really working the truck there shold not be any significant damage. Pulling the pan would confirm any damage.

 

[cerberusiam]

The trans is a 47RE, it is 14 years old (unless a rebuild can be verified), and the TQ is a killer on the clutch packs even empty and normal driving. Pan may or may not show issues if it slipped the clutch packs enough to glaze the frictions but not enough to really slip them hard yet. Pan needs inspected and fluid changed.

Given there is no indication of the amount of time the TV cable has been disconnected and what was done with the truck before the OP got it, "suspect" is applicable. If it would have been since March and he did nothing but minimal driving then I would agree it should not matter too much, not the case though.

 

[MarkEagleUSA]

The trans is a 47RE, it is 14 years old (unless a rebuild can be verified), and the TQ is a killer on the clutch packs even empty and normal driving. Pan may or may not show issues if it slipped the clutch packs enough to glaze the frictions but not enough to really slip them hard yet. Pan needs inspected and fluid changed.

Given there is no indication of the amount of time the TV cable has been disconnected and what was done with the truck before the OP got it, "suspect" is applicable. If it would have been since March and he did nothing but minimal driving then I would agree it should not matter too much, not the case though.

Now you guys have me sweating bullets!

The transmission appears to have been painted silver which usually indicates it's been out of the truck, right? So I'm guessing it was recently rebuilt although the dealer I bought it from couldn't confirm because they got the truck at a wholesale auction. They also claim they did not see or know about the disconnected TV cable (yes, I did contact them late last week).

Since reconnecting the cable the truck seems to perform much better. While I understand the need to drop the pan it's not something I can get to before the upcoming holiday. The fluid is still very clean and does not smell burnt at all. The transmission is shifting properly (at least as far as I can tell) and I cannot detect any slippage at all. Hopefully it won't grenade on me before I can get to the drain & fill.