700r4 limitations

[raunch]

For better or worse, I'll soon be swapping in a 700r4. Not an '89 or later, but it's recently been rebuilt, to what extent is not yet known. I hoping for some upgrades in it, as the rebuild bill was a couple thousand. But I have no idea what a baseline 700r4 rebuild costs.

Anyway, I'm wondering about towing with a 700r4 and what experience you all have towing with one. My towing consists of 1) a pop up camper trailer that weighs about 2,500 lbs loaded or 2) a raft and trailer that weighs about 700 lbs. I hoping that as long as keep a careful eye on the tranny temps I can use OD to tow along the flat stretches of road.

During the swap, I'll see about tranny cooler upgrades, but I am not too sure about what else to upgrade without doing another rebuild. I would like 3rd and 4th lock-up. Should I get a better converter if it needs one-does that make sense if nothing is done internally? Any other thoughts?

Thanks.

[convert2diesel]

There are a number of internal weaknesses inherent to the 700R4. As far as towing the weights you suggested though, you shouldn't have any problems. Put over 50,000 miles on one pulling a 3,000 lb. Coleman pop-up. The one co-docile to that is you will find running in OD a stretch. Use 3rd locked. It will make your life easier. If you insist on using 4th, you will have to replace some internals to handle it. 4th on these were never ment to pull any weight.

If the tranny came off a gasser, you will have to replace the govenor at least plus I would suggest you also install a 3-2 downshift delay throttle valve and what the industry calls a "Corvette servo". The throttle valve will prevent the 3-2 downshift unless you really get in to it on a hill and the servo will tighten up the shifts. These can all be replaced with the pan off and don't require the tranny to be disassembled.

All of the 700s I have had, do lock up on their own in both third and fourth but as you are replacing a 400 (I assume) you may not have the wiring or ECM to lock it up on its own. This is a simple fix with a switch on the dash controlling the gound and the power going through the brake pedal.

I would also suggest a good low stall torque (1,200 RPM stall) to replace the factory one. These are typically marketed as diesel torques but some automotive applications also used this stall speed. Pay special attention to the friction materials used for the lock up. Otherwise you should be good to go.

Hope this helps

Bill

[raunch]

Thanks, it does help. I was wondering about a manual lock-up switch

The 700r4 will come off a Jimmy with a 6.2. I'm getting the whole Jimmy, mostly for the tranny, but there will be some other parts to use as well.

[convert2diesel]

What year is the Jimmy? Make sure you get all the tranny control bits off it to give you automatic lock-up. Otherwise disregard everything said above except for the servo and the throttle valve. WIll have the diesel torque and govenor and all the diesel related internals.

Bill

[raunch]

I think that the Jimmy is an '84. I'll pull every bracket/bolt/wire/cable hooked to the tranny and I'll keep the throttle valve and servo in mind. I'll get the paperwork from the rebuild and call the shop if I need to. My fingers are crossed that some of these upgrades have already been done.

Another component I am wondering about is the column. Main reason being is that my shift lever is broken in the column such that it can be moved freely through the range of gears. No big deal for me, but it could be a safety issue, especially with kids in the truck. So can the columns swap too, or would it be easier to open up my current column to fix the shift lever?

[convert2diesel]

More then likely, the columns will swap over. Probably easier then taking the current one apart.

Your best bet is to spend a few bucks with ALLDATA DIY

http://www.alldatadiy.com/?gclid=CLD...FQk65Qodo39I0w

and get the subscription for both vehicles. The wiring diagrams will pretty well tell you what you need from the donor truck to get your tranny working properly.

Bill

[raunch]

Got the tranny out and turns out it is a 'K' case. I'm going to have a HD converter built and the end of February and in the meantime put together the other little parts I need.

One question about the corvette servo...Does it tighten up the shifts only or is it more reliable and durable? Or do tighter shifts = reliable/durable? One tranny guy I talked to said he has pulled them out after customers wanted one put in, because the shifts were too hard.

A side note: when I dropped the tranny out of the donor rig, I forgot to disconnect the TV cable. The cable snapped about in the middle, and I am hoping that the big tug on it did not damage something in the tranny.

So begins the project.

[crashz]

The Corvette servo is simply a big piston actuator that applys clamping force to the 2nd gear/rev band on the drum. With a shift kit it may produce a harsh shift, but the accumulator springs will really dictate that, not necessarily the servo. This is a great mod and really helps with the life and durability of the unit.

I can't remember what the TV cable is hooked to within the valvebody, but you'll want to pull the pan and take a look. I haven't had one open for more than 15 years, so hopefully someone else here has a better answer for you.

[raunch]

There was a shift kit installed when it was rebuilt, regardless I think I'd like to try the corvette servo. I will need to sit down a bit with the tranny guy and talk over things like this. He did the rebuild after all, and I hope he would know how the servo would affect the shifts and what can be done for a less than harsh shift.

Thanks for the info.

[convert2diesel]

A side note: when I dropped the tranny out of the donor rig, I forgot to disconnect the TV cable. The cable snapped about in the middle, and I am hoping that the big tug on it did not damage something in the tranny.

For sure if you put that much force on it, check the throttle valve actuator. WIth luck all you did was snap off the cable lug but you may have broken the actuator. At the very least check for full travel of the throttle valve.

This is the primary control of the tranny and must work properly!!!

Bill

[raunch]

Good to know. I'm going to take the thing into the shop that did the original rebuild and have them do the upgrades and make sure I didn't ruin anything.
Thanks.