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700R4 problems

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Smokeyk5

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Howdy all, have some questions in regards to my newest k5 and some drivability issues. I have searched and done what has been recommended to fix the issues but it still has not fully fixed them. I have a 75 with a 700R4 np208 swap done by the previous owner has 3.73 gears (I had a previous post concerning the gears and they are the same F and R) and 33" tires. I have some gremlins I'm trying to get figured out and am not too familiar with the 700R4 and it's "problems". In regards to the trans it seems to shift weird, by weird I mean when up-shifting from 2-3 or 3-OD it feels to lose power when shifting, 1-2 is fine but the upper gears just don't feel "right" they are not crisp shifts more of gooey and soft. I'm not expecting it to shift hard but its way too soft for my taste. It doesn't feel like the trans is slipping but more of a brief bogging down before it shifts to the next gear than once it's in gear it's fine. The best way I could describe would be driving normally than hitting a patch of molasses when it shifts. I have checked the fluid and adjusted the TV cable numerous times. Originally the TV cable was not properly set and I don't know if that had some detrimental effects to the trans that is causing the problems or if there are others issues I need to address, needing a filter and fluid change, TV cable just not working, ect? It also hates to down shift from OD to 3rd when climbing a grade at WOT, Most times I have to manually down shift from OD-3 and even when I do it feels no different power wise until it flattens out. 3-2 is fine or driving under 40MPH's and it downshifts normal when coming to a stop. The other issue and I'm not sure if this is from me being used to my car that does 0-60 is under 5 seconds but the K5 has NO power once past 40 mph, getting to 65 is a challenge. The motor was rebuilt (again previous owner) with a mild cam, headers and HEI ignition and has maybe 5000 miles on it but it just has no balls when trying to get to get past 50 or going up steeper hills. It has good torque of the line and is fine around town but going on the highway is a pain. I feel no real power band increase with higher RPM's regardless of the gear, it is just an initial torque and than nothing at higher RPM's. Would that be a trans problem or is it just a fact of an older truck designed for 55 MPH highway speeds? Any input is appreciated
 
I don't know a lot about transmissions, so someone else will be more help, but have you changed the fluid? You said the TV cable was out of adjustment. That can heat up the tranny. Once the fluid overheats, the damage is done, nothing will make it better short of changing the fluid, assuming that there isn't any other damage done, too. Just a thought.

Also, I have an 88 with a TBI (and most of the "ultimate" TBI mods done), stock cam, long tube headers, 700r4, 3.73 gears, 31" tires, and it will pull well past speeds I'm comfortable driving it at. Not your exact truck, obviously, but if everything were right I wouldn't expect you to lose power at 40 mph, definitely not with 3.73 gears and 33" tires.
 
I have not changed the fluid/filter I was planning on it just wasn't sure if these were more signs on the tranny just being toast or what was going on with it. The tranny has maybe a few thousand miles on it, but I know with the misadjusted TV cable it will eat that thing up quick. The fluid does have a slight burn smell to it nothing overly strong and is slightly dark but still some pink Are there other things I could check as well?
 
If timing is jacked up, the 2-3 shift can be sketchy. That's the only one with an overlap - one clutch is engaging while the band is releasing. The rest are simpler and should shift simply.

As stated, the 1st thing is to make sure the TV cable is adjusted right. Make sure the fluid level is right. Drop the pan and look for obvious problems and make sure the filter is actually seated in the pump intake. Some say not to change the fluid when it's really old, but I don't like that idea. If it can't run on good fluid, you're on borrowed time no matter what.

If the above are fine and every shift sucks, the line pressure may be low. You might have a problem with the pump or a leak somewhere. Or your TV may be stuck in the valve body. A pressure gauge is helpful. If all the shift point are really low, the governor may be stuck or the gear stripped. The governor is easy to pull and inspect with the tranny installed.

Please confirm that the torque converter is locking/unlocking based on throttle level and brake pedal application. What year is the vehicle?

However, don't be too quick to conclude the tranny is to blame.
 
Blue85 said:
Please confirm that the torque converter is locking/unlocking based on throttle level and brake pedal application. What year is the vehicle?
Click to expand...

I know some people put a checkball in the TCC solenoid so that it locks up the converter without electrical input, but would this affect shift feel? I'm not sure if that would then unlock during shifts like it would have when electrically controlled.

Curious, as this is a retrofit and rebuilt trans, if that is/was the case...
 
I'm subscibing because my tranny does the samething you are describing sometimes. Do u have a cooler on yours? I really want to figure this out:popcorn:
 
If the engine isn't running well,the tranny will suffer also--and be blamed when in fact it might not be at fault...be sure your exhaust isnt blocked up by a plugged up catalitic converter or crushed pipe or a double walled pipe that collapsed internally (a vacuum gauge can help diagnose that)..

It could be the stator in the torque converter has seized in one position,that usually causes poor accelleration and limits top speed..makes if feel like the trans is stuck in too high a gear,for lack of a better description...
 
The problems with putting 700r4s into vehicles that didn't have them. It's not a th350 or th400 that you can just toss in. and it'll be fine. But good thing is it can all be fixed right, regardless what the PO did to it.

What engine/carb are you running. The throttle valve cable needs a special bracket if it's not hooked up to a rochester (or IP on diesels) that came with a 700r4 factory. Shifting is controlled by fluid pressure via the TV cable, and it requires a specific geometry to operate properly.

IIRC Torque converter lock up was controlled by the ECU. I'll assume that's gone cause it's in a 70s rig. Multiple ways of changing that. A electrical version used with a toggle switch, and then you can also lock it up in 2-4. Automatic lockup kits, All sorts of kits out there to control lockup for non-factory use.

All of these problems can be addressed. Check out Bowtie Overdrives and do some reading.

Its super bad juju running the 700r4 without those things fixed, just a matter of time. Bowtie overdrive have all the items to fix this (though it can be built yourself), but even better they have tech articles how a 700r4 works, and problems that can be associated with them, if they're not installed properly.

TCI is another who makes stuff, B&M too. But specifically for the proper TV bracket, I'd go with BTO.
 
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This I will probably need to have a trans shop check. from everything I read about adjusting the TV cable it should be set correctly, but as I said before it was not done right and I'm not 100% sure on it.
 
It's a 75 but the trans is from a 90 k5. The shift points (mph is good) under normal acceleration, but that is also when it goes through a sluggish shift. At WOT is just doesn't build enough RPM before shifting and shift a little firmer but still kinda gooey. How would I check to see if the converter is locking up?
 
mrschaeferpants said:
The problems with putting 700r4s into vehicles that didn't have them. It's not a th350 or th400 that you can just toss in. and it'll be fine. But good thing is it can all be fixed right, regardless what the PO did to it.

What engine/carb are you running. The throttle valve cable needs a special bracket if it's not hooked up to a rochester (or IP on diesels) that came with a 700r4 factory. Shifting is controlled by fluid pressure via the TV cable, and it requires a specific geometry to operate properly.

I'm currently running a 350, not sure on other aspects as the PO had it rebuilt, currently has a quadrajet and he used the TCI TV cable kit for it and it should be the correct one from the model # i cross referenced. I do have a TBI from a 90 1500 I was planning on tossing on that was original hooked to a 700r4

IIRC Torque converter lock up was controlled by the ECU. I'll assume that's gone cause it's in a 70s rig. Multiple ways of changing that. A electrical version used with a toggle switch, and then you can also lock it up in 2-4. Automatic lockup kits, All sorts of kits out there to control lockup for non-factory use.

All of these problems can be addressed. Check out Bowtie Overdrives and do some reading.

Its super bad juju running the 700r4 without those things fixed, just a matter of time. Bowtie overdrive have all the items to fix this (though it can be built yourself), but even better they have tech articles how a 700r4 works, and problems that can be associated with them, if they're not installed properly.

TCI is another who makes stuff, B&M too. But specifically for the proper TV bracket, I'd go with BTO.
Click to expand...


I have been putzing on BTO I will may give them a call and see.

Thanks
 
Smokeyk5 said:
It's a 75 but the trans is from a 90 k5. The shift points (mph is good) under normal acceleration, but that is also when it goes through a sluggish shift. At WOT is just doesn't build enough RPM before shifting and shift a little firmer but still kinda gooey. How would I check to see if the converter is locking up?
Click to expand...

That's a good question I don't know the answer to. Searched and found this, if it helps. http://www.f150online.com/forums/tr...l-if-my-torque-converter-locked-unlocked.html Makes sense to me.
 
Unless someone installed a kit in that for lockup, it doesn't have it. Crawl under truck, look at drivers side of trans for a 4 pin connector. There should be wires going to/from that, should trace to brake pedal and vacuum switches (factory setup without computer) or to whatever aftermarket TCC lockup kit was installed, if any.

Starting to sound to me like somewhat of a hack job, hopefully my thoughts are ill-founded!
 
Yup or the PO didn't know better. I know my first 700r4 K5 I made some pretty stupid mistakes not knowing how what I was doing affected that trans :doah:
 
Ya, after seeing how the TV was connected I was figuring something will eventually crap out, love other peoples "handy" work, but i would rather deal with the trans problem on the new one compared to the rust on my other K5. I will check the lock up when I get home tonight. Thanks
 
Lock-up is easy to check. Just cruise down the road and lightly tap the brake pedal with the left foot. The rpm should come up like 100-200.

Without the ECM, the lockup won't work "right", but it could be good enough to not damage stuff. Even though lockup was controlled by the ECM, the shifting was not, so there must be at least a 4-3 downshift switch on the valve body. But you'll have to confirm that the solenoid is still in series with it. (Shifting with the TCC locked is silly and greatly shortens TCC life. It's also harder on everything else in the tranny).

You really want lockup controlled by vehicle speed, engine load, shifting and brake pedal. The non-ECM trucks used a vacuum switch for engine load and governor pressure and current gear for vehicle speed, plus the downshift switch(es) I mentioned above. The ECM knew MAP and VSS, so it could replace some of those (plus better coordinate with EVAP purge, EGR, etc.). These aftermarket vendors have solutions, but I think it's better using the factory parts from carb trucks to mangage the lock-up in 3rd and 4th only.

But lock up may not be the issue here, so I'll stop rambling....
 
Alright so I checked this weekend, I'm almost positive it has a lock up. From underneath there was a connector that goes into the trans did not look like the TV connection that I have been seeing other places, the hook design. This was a 4 pin connector as dyeager535 descibed. Hopefully with the TBI swap I can just get it all taken care of and have enrything working the way it should. I also did figure out that the TV cable was not set right though. My issue was the postition of WOT and the geometery not being correct. When I was reading about setting the TV cable for WOT, I was under the assumption that I needed to do this by hand and turn the throttle cable all the way in order to "set" the position. The problem I found and this may not be everyones is that my pedal WOT was not nearly the same as when I set it by hand. In turn what I thought was WOT when I stepped on the gas was still just normal throttle position to the TV cable. My guess for the sluggish shifts is that the trans was having an issue with the line pressure compared to the speed govenor and couldn't decide to shift when needed. After adjusting it literally was a new truck, shifts are smooth but noticable, it can actually get some RPM and power, it downshifts when it should and I can do 65 now. Hopefully, there was not to much damage but I will probably rebuild it anyways in the near future anyways. Thanks everyone for the help
 
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