700R4 Lockup??

[bluex]

Well I got my lockup wired up all except for the brake cancel switch. I put it on a toggle switch so I can turn it off when I'm slowing down. This weekend I drove it to work sat and sun. Its all back roads and I was running about 60-65. It was turning around 1500 locked. Even the smallest hill or incline would have it hunting back between 3-4. I would have to give it more gas to get it to say in third. With it unlocked in 4 it runs about 2k. It would only downshift then on a good sized hill and no hunting just straight to 3. Will it hurt anything to run in OD with it unlocked? I'm thinking my main problem is not enough gear (3.08) for the speeds I'm going to run normaly. I hate the interstate and aviod it whenever possible so my main crusing speeds are under 70. To get about 2k in lockup @ 65 I'm thinking I need at least a 3.73 gear? I'm not planning on gears anytime soon so I'd like to just run in OD and save the lockup for the highway.

Here is a list of the stuff done to the tranny:

New frictions/bands--Black High temp/High energy
HD Pump
'Vette Servo
Mod lube circuit
2-4 band reinforced
29 element GM HD sprag
2k reman 'vette stall

I bought it off ebay from a local (linclonton NC by swervin) shop. It has a 12 mo warrenty. Look here for one of his auctions. http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WDVW

I'm really happy with it other than the above problem. It also runs the gears out at light throttle to 3k. Seems a little high to me, but probably has something to do with the shift kit.

Thanks
Paul

[bluex]

bump, anyone got any ideas??

[Grande Rojo]

I dont use the lock up on mine at all.

[bluex]

So I suppose it wont hurt it then? What gears are you running? I like the take off with the 3.08s but I just think they are not enough for the OD.

All the people on here that have done these swaps I figured I could get an answer???

[swervin ervin]

Paul,

if it's unlocking real easy such as when going up a hill or with little pedal pressure you need to change the low vacuum switch. I had the stock switch on mine and it would unlock too quick. I swapped it for another switch that takes a bigger vacuum drop before letting it unlock. The part number is 14014519.

This is the switch that's mounted on the firewall behind the brake booster. I checked both the stock one and this one with a vacuum gauge. The stock one would switch at something like 7 inches of vacuum and the new one something like 4. These numbers may not be exact since it's been so long ago, but you get the idea.

[bluex]

Its not unlocking at all. It will got straight from locked in 4 to 3. I used the vaccum switch you recommend in your write up on 73-87 (14014519). I have it wried that way minus the brake cancel switch. I think you said that one was 7.5 in? Would having it hooked up to the ported (no vac at idle) port on my 1406 be a bad idea? I'm thinking that maybe its cutting the vac off too soon on that port. I also notice it locking/unlocking. I can hear the engine go up and back down but only a few hundred rpms. It seems to be doing a little better now, but I could just be getting used to driving it so it wont downshift?

[swervin ervin]

I have mine hooked up to manifold vacuum. I've never tried it on ported so I don't know what the difference would be. One thing is for sure, high rear gears are bad for these things. I've had it both ways, with 2.73's and now 3.73's. It stays in 4th most of the time now except for when I get below 40 mph, unless I get in it. Mine locks as quick as it goes into 4th. I can lay my foot on the brake pedal and cause it to unlock by canceling it with the brake switch.

As I've said many times, what in the world was GM thinking with a OD tranny and high gears?

[Greenlee]

I think I have the same problem. Well, I didn't realize it was a problem until reading about it on this board. I have a 700r4 with high gears. I don't know the exact gear ratio, but the previous owner told me they were high. From about 50 to 65 mph it down shifts on small overpasses and such. If I keep it over about 70 mph it seems to stay in overdrive. Am I in danger of burning up the transmission? This may be a dumb question, but how do I know when the torque converter is locking up?

It has 30 inch tires. If I switched to some low profile tires in about a 28" or 29" wouldn't that be sort of a poor man's way of getting a higher gear ratio?

[swervin ervin]

The biggest thing that kills 700-R4's is heat. Going in and out of OD is just as bad. Out of lock, the converter is slipping and causes heat. Combine the two and you are looking at replacing it down the road. Towing and hauling heavy loads, with high gears, with the shifter in OD is certain death.

Every 700-R4 needs a external cooler added to mix. This will keep the heat under control. As for locking and unlocking, or dropping into 3rd, this will only be addressed with lower gears. Smaller tires reduce the feel of the rato, so yes a smaller tire will seem like you have a tad lower gear.

GM needs to have their butts kicked for even offering a OD tranny in a truck with 2.73 gears. No wonder they all died an early death. These year trucks were mostly used as work trucks in the first place. Why did they think they needed this combo???

The tranny can be in 4th (OD) without locking of course. The lockup converter was used as a way to make them last longer, i.e., no slippage. To see if it's locking, while cruising along, lay your foot on the brake pedal lightly. You will feel the engine rpm raise up about 200 to 300 rpm. Let off and you can feel/hear it go back down.

[bluex]

Mike,

What kinda rpms do you run @ 65 or so with the 3.73's? I was thinking a 3.42 or 3.55 would be almost prefect, but I think I can get a set of 3.73 for a reasonable price. Just wondering what kinda rpm increase I would be looking at.

[swervin ervin]

I have 27" tires and with the 3.73's and locked in OD, I'm turning right around 2100-2200 rpm at 65. Best I remember at 70 I'm at 2200. Believe it or not, my gas mileage (like I really worry about it that much) actually went up when I switched from 2.73's to 3.73's. I contribute this to it staying in OD easier. Before the switch in gears, it was like you say, constantly going in and out of 4th, with the least little incline or hill.

3.55 to 3.73 gears is a perfect range with a 700R4 tranny. 1st gear will change in a heartbeat because of the very low 1st gear the tranny has, but it makes for a perfect driver. I bet money you won't regret the change. Anyone who has swapped for lower gears with a 700 will tell you the same I'm sure. I would go with the 3.73's if I was you.

Mike

[bluex]

Thanks Mike thats what I was really looking for. I guess I'll get after that guy at work who mentioned having an extra 3.73 rear laying around. I'll have to go see if it will bolt in my truck, or I might just have to learn how to set up gears.

[Grande Rojo]

I run 4.11's in the rear with 31" tall tires and 4th gear is great, 2200 rpm @70 with no lock-up.