Thread: 700r4 shifting

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Ok, got an issue, hope you guys can diagnose it across the net. My truck's th350c took a dump on me and so I had a shop rebuild a 700r4 and put it in. They used the brake switch I had for the th350c for the 700r4 lockup. Anyway, when I start with the engine cold, the transmission won't shift from 1st to 2nd with light throttle below like 22-25 mph. I could hold it at 20 and hear the engine get loud before it shifts. If I get it hot, then turn it off and then turn it back on, it shifts at around 10-15 mph. Purty sweet. The shop took the valve out, found nothing wrong with it but replaced it with another one but it's still doing it. Anybody got any ideas on the problem?

Originally Posted by BigRedTrucker

Ok, got an issue, hope you guys can diagnose it across the net. My truck's th350c took a dump on me and so I had a shop rebuild a 700r4 and put it in. They used the brake switch I had for the th350c for the 700r4 lockup. Anyway, when I start with the engine cold, the transmission won't shift from 1st to 2nd with light throttle below like 22-25 mph. I could hold it at 20 and hear the engine get loud before it shifts. If I get it hot, then turn it off and then turn it back on, it shifts at around 10-15 mph. Purty sweet. The shop took the valve out, found nothing wrong with it but replaced it with another one but it's still doing it. Anybody got any ideas on the problem?

I'm not an expert with transmissions or anything, but could it be that they didn't set the line pressure right? That is very critical with 700R4's to work right from what I've researched.

Would that cause it to shift fine after it's been warmed up, turned off and restarted? I mean, I put it in park after it's warmed up and then back into drive, same stuff. Restart it and it works good? This is just driving me nuts because this truck is supposed to be a daily driver but the guys at the rent-a-car shop know be my name now.

On a 700/R4, the line pressures are critical, and they are controlled by the TV cable. In order to set the TV cable properly, the trans shop needs to install a pressure gauge and watch the pressure in each gear. Get the TV cable set up wrong, and you've got a boat anchor.

It looks like you guys might be right. I looked at transmissioncenter.net and it says you need a special bracket for edelbrock or holley carbs and I'm running a performer. It says it fixes the "Hard" 1/2 shift. Yay!

Your tv valve is sticking very common in 700 r4s even in rebuilds they are very sensitive to contamination. You may be able to fix it if the trans shop installed a helper spring behind the valve. pull on the tv cable about 20 times without the motor running drive it try it again when its hot and shifting properly The valve is machined to clean itself so strocking it my work if it doesn't you need to pull the valve body

BRT commented that the shop replaced the valve. Makes me think that they either missed contamination in that passage or he has a servo problem. If clutch packs are clearanced (and they need to be a touch loose), then the band apply servo is not getting proper pressure from something like a broken ring seal or sticking piston or gunk in the bore. The way he describes the warm up, shut down and restart, it is possibly warm enough to free the piston from sticking during it's travel in the bore. Another could be 1-2 shift shuttle valve is hung up from galling or debris. Warmth and fluid loading in the channel makes it return to normal. It's hard not being hands on to see it first hand. 700R4 needs proper band apply for 2nd gear. I worry that it is slipping until it gets enough pressure to grab and hold. Keep your attention on fluid for a burned smell. The quicker this is resolved, the better that band is gonna like it. Good luck BRT.

Well, the shifting seems better. How do I know what burned fluid smells like? I've lost a lot of gas mileage since adding the extra gear. The fluid's still pink on the dipstick and kinda smells hot. I need to find another car so I can put this vehicle down for awhile. Could it be the cam that causing the lower gas mileage. The 305 is easy to overcam.

Mercon/DextronIII does have a funky hot smell even when it's doing it's job. I would recommend an external cooler for the tranny even if you're not towing anything or "Romping" on the throttle very often. I am curious though, are your shifts back to normal, or could thay be better for your driving?

I have an external cooler. Although it's on the inlet side for the radiator, so it hits the cooler first AND then the radiator. Shifts seem normal, a little firm, but it's supposed to be. It's hard to get used to have another gear to shift too, but I'm still wondering about going from 16 to less than 13 on the highway with adding overdrive and fixing the miss. Thanks for putting my mind at ease about the smell.

Just an update: there is some noise from the transmission, especially when pulling to a stop, some "Urnh-Urnh". I thought maybe it was coming from the shift kit. I also have an electronic spark control distributor even though there's no computer. You think the noise from the transmission can make it seem like there's "knock" and cause the ESC to retard the timing?