700R4 started shifting really high RPM

[backwoodsman]

Hi all,

My 700R4 (behind a 6.2L diesel) just started shifting at really high RPM, pretty close to full-throttle RPM's most of the time. It acts like the TV cable is stuck at or near the full throttle position, but it's not stuck and moves normally, and once in a while it'll shift pretty close to normal RPM. Fluid level is fine, and the fluid is good. Makes no difference whether it's cold or hot, acts the same either way. It was rebuilt around 60K-70K miles ago and it's worked fine ever since, until the last 200 miles or so of a recent road trip, when this started. Any ideas? Stuck governor maybe?

Thanks.

 

[Blue Ox]

My guess would be that the throttle valve itself is stuck. So it's shifting on the governor, not throttle position. I believe there's a kit available with an assist spring to push the valve back.

There's much better transmission people here that can probably direct you to thr correct item.

 

[backwoodsman]

My guess would be that the throttle valve itself is stuck. So it's shifting on the governor, not throttle position.

Thanks for the reply. I was thinking the throttle valve is less likely because the cable seems to move normally. But I don't know how it's hooked up inside the transmission; maybe there's a spring in there that will make the cable return even if the throttle valve is stuck open? The cable has a bit of slack at the idle position, which I don't remember being there before, but it's been a while since I installed it so I may not be remembering correctly. Maybe that's a sign of a problem with the throttle valve?

I'll pull the governor and get a look at it as soon as I have a chance, but that may not be today. I read on another forum about jamming the governor weights in the out position just to test, so will try that if the governor looks OK.

 

[Blue Ox]

Again, there's WAY better transmission guys here than me, and it's been a long time since I've had my hands in a 700R4, but IIRC, the cable moves a lever that pushes up on the valve. So, if the valve sticks the lever returns and the valve stays put. Thus the transmission thinks you're at WOT and holds the gear until the governor forces an upshift.

The cable is not linked to the valve, it just pushes on it. The valve relies on fluid pressure to make it follow the cable back when you come off the throttle. Hence the kit with the spring for sticking, or just faster response.

Where is @NickTransmissions when you need him?

 

[PrairieDrifter]

The cable moves the valve itself. It's basically just a little plunger, then the cable has a hook on it that just slips through the top of the valve. I can't remember the spring setup, but the cable itself does not have a return spring.

 

[89Suburban]

Yup I think Transgo makes a new plunger kit just for this problem if I remember correctly. That happened to Silvy Burby when I still had her. Somebody on here recommended that to me and it fixed it.

@yevgenievich is the one that recommended it.

 

[89Suburban]

Here is the thread

Cold snap starts shift issues on 700R4

Thanks for the input. I think that is exactly what is happening. TV cable or valve is sticking when it gets too cold out. If that is the problem, the fix is in the jr shift kit and involves dropping a valve body. There is a spring and a metal stop that goes inside the assambly of the valve.

www.gmsquarebody.com

 

[NickTransmissions]

Where is @NickTransmissions when you need him?

Building transmissions, lol...Coincidently, I have two 700R4s going back together as we speak.

I also suspect TV valve sticking, another mentioned Transgo's TV boost valve which is the way to go - I install them (and that shift kit) in all my 700R4s.

Thanks for the reply. I was thinking the throttle valve is less likely because the cable seems to move normally. But I don't know how it's hooked up inside the transmission; maybe there's a spring in there that will make the cable return even if the throttle valve is stuck open? The cable has a bit of slack at the idle position, which I don't remember being there before, but it's been a while since I installed it so I may not be remembering correctly. Maybe that's a sign of a problem with the throttle valve?

I'll pull the governor and get a look at it as soon as I have a chance, but that may not be today. I read on another forum about jamming the governor weights in the out position just to test, so will try that if the governor looks OK.

The governor valve can also stick, causing similar symptoms so when you pull the governor, turn it upside down in your hand and actuate the weights...You should see the governor valve moving freely as you work the weights in and out, so to speak. Check the condition of the gear while you're at it - if it shows signs of wear (or if the valve is sticking) punch out the roll pin holding it in place and yank it off...If the valve isn't moving when you do your test, remove it and polish the inside of the bore with bench buddies...These are small abrasive hones that can help remove small rough spots in bores to relieve sticky valves. Then install a new gear once you're all done...This is a good service to do regardless...

As far as the TV boost valve, main spring, plunger and sleeve are concerned - you can have a valve sticking regardless of how the TV cable feels as the primary spring will still provide tension for the cable. So if the TV valve is sticking, you'll have late upshifts, early upshifts or no upshifts, depending on where exactly it's hung up.

I'd conduct a line pressure test at idle then at stall to see what your values are at those two settings...If your line rise is poor or erratic at either setting, it's a sign the TV valve is sticking. Drop the valve body, install the Transgo SK700R4 shift kit, including their TV valve...Drill the plate per their instructions, if this is just a cruiser.

There's other things you can do to the valve body but you can let me know if you plan on modding it and I'll post a few other tips/pointers...

 

[backwoodsman]

The governor valve can also stick, causing similar symptoms

Thanks for the very detailed response. I still haven't been able to get back to it, but expect to tomorrow. In the meantime, from the symptoms, do you have an idea of whether the TV valve or governor is the more likely culprit? I'm planning to start with the governor since it's easier to get to. If I have to get to the TV valve, I'll definitely install that Transgo part.

 

[NickTransmissions]

Thanks for the very detailed response. I still haven't been able to get back to it, but expect to tomorrow. In the meantime, from the symptoms, do you have an idea of whether the TV valve or governor is the more likely culprit? I'm planning to start with the governor since it's easier to get to. If I have to get to the TV valve, I'll definitely install that Transgo part.

Probably the TV valve but it's good to check both...I'd do the line pressure test before you take anything off/out.

Let me know if you need instructions for conducting the test.

 

[Craig Nedrow]

Hi all,

My 700R4 (behind a 6.2L diesel) just started shifting at really high RPM, pretty close to full-throttle RPM's most of the time. It acts like the TV cable is stuck at or near the full throttle position, but it's not stuck and moves normally, and once in a while it'll shift pretty close to normal RPM. Fluid level is fine, and the fluid is good. Makes no difference whether it's cold or hot, acts the same either way. It was rebuilt around 60K-70K miles ago and it's worked fine ever since, until the last 200 miles or so of a recent road trip, when this started. Any ideas? Stuck governor maybe?

Thanks.

Is that a stock setup? I did not know that a 6.2d had that transmission. Reason, I have a TH400, but have a 700r4, would really help going down the road at 70, I don't go over 65 the way it is.

 

[NickTransmissions]

Is that a stock setup? I did not know that a 6.2d had that transmission. Reason, I have a TH400, but have a 700r4, would really help going down the road at 70, I don't go over 65 the way it is.

Yep, some of those 6.2Ds had the 700R4s...The governors came with slightly heavier weights and springs to promote earlier shift points but I don't think anything else about the diesel units are different than the V8 gas versions. TC may stall a little lower as well but that's it AFAIK.

 

[backwoodsman]

Is that a stock setup? I did not know that a 6.2d had that transmission. Reason, I have a TH400, but have a 700r4, would really help going down the road at 70, I don't go over 65 the way it is.

Yes it's stock. My understanding is, 1/2 tons got the 700R4, 3/4 tons got the TH400. I assume the reasoning was, 3/4 tons are more likely to get worked a lot harder, and the 700R4 is pretty borderline in a full-size rig even without that, unless it's been rebuilt with some stronger parts. A 700R4 might be an option for you, but Nick would know a lot more about that than I do.

I still haven't gotten back to it, but going to try really hard to check the governor tomorrow. I'm thinking it's probably the TV valve, but the governor is easy to check first. The governor cover is stuck on with RTV silicone, which the shop that rebuilt it years ago must've done, so hopefully I can get it apart without bending it.

I don't have a gauge to do a pressure test but could buy it if necessary. But it seems to have plenty of pressure; when it finally does shift it snaps into gear pretty firmly.