700R-4 problems/questions

Jack Boelte · October 11, 2001

I've got an '84 Suburban with the 350/700-R4. When accelerating on the highway from 65 up, it feels like it's slipping. When I let up, then ease into it, it feels right.

I have seen black stuff on the dip stick, slipping I'm sure. Fluid was a little low, I haven't driven since I topped it off. I had a good trans. shop take it apart about 2 years ago, they replaced the 4th gear band, said it was burned. I had the shop adjust the TV cable, he seemed happy with it.

I suspect low pressure to the 4th gear band. I think the torque converter lock up clutch is working good. Is there a particular valve that may be leaking? I have a Haynes transmission manual, it's typical of a Haynes manual...:sneek: leaves a lot out. Would a B&M shift kit be a good band aid? Would it direct more pressure to 4th gear?

Thanks

76BBSub · October 11, 2001

I'm certainly no expert on trannys, but I would guess that if the fluid is burnt that you have internal problems which can't be fixed by a shift kit. All the shift kit does, as you mentioned, is change the pressure applied, how quickly it is applied, and at what RPM/vacuum level. I would recommend changing the fluid, if it is black then it has been rendered ineffective and you will have more problems regardless of what you do. Try taking it to another shop and see if they can adjust it and flush the fluid and get you a few more miles, but I am guessing that you are looking at another rebuild.

But I could be wrong....

Jeff

95 Silverado · October 12, 2001

the band in a 700R4 is used for both 2nd & 4th gear, and there is no adjustment on it, if the problem appears only in 4th gear it is probably bad clutches. It is probably too late for a shift kit . Try the fluid/filter change, see what is in the bottom of the pan when you take it off, a coating of clutch residue is normal, metal particles and burned fluid are indicators of trouble. If they are present have them put the shift kit in when they rebuild it.

Jack Boelte · October 15, 2001

It seems that it starts to slip if the fluid level gets low. I do have a leak at the speedometer gear, so I know what I need to fix. Maybe if I fix the leak and keep the fluid topped off it will last a while.

I am wondering if there is an O ring or seal that is leaking for the 4th gear actuator. I'll have to read my book some more...

76BBSub · October 15, 2001

Yup, low fluid level will make them slip, and it's VERY bad for them. Even if it isn't low enough to slip the low level also contributes to higher fluid temps, since there is less fluid in the pan, therefore heats up more quickly. This is also really bad for the tranny and will shorten the life.

Jeff

Jack Boelte · October 15, 2001

It's got an external trans fluid cooler, I'll bet that holds half a quart or so. I wonder if I should add a little bit more fluid, so it reads a little over full?

76BBSub · October 15, 2001

A little extra shouldn't hurt, but if it gets hot and is too full there is a relief valve that will blow the excess fluid out. Usually makes a pretty big white smoke cloud behind the truck, but doesn't really hurt anything...It will scare the crap out of you the first time you see it, though.

Jeff

Jack Boelte · October 15, 2001

Yeah a big puff of smoke would scare the crap out of me!

76, don't you have a job? Why aren't you working instead of cruising the forum?? j/k

The truck does fine in town or on the rural highways, it's only the interstate where it has problems. When I get one of my other cars up and running, I won't have to take the truck on these trips. That'll be nice, better for gas too.

76BBSub · October 16, 2001

Yeah, I gotta job, but it's hard to resist checking in a few times a day! Usually I check the main Forums once or so, but check Classic a little more often, especially when we have some good threads going like we have this week...

I just can't quit!!

Jeff