700R4 - essential to buy a newer case?

[bmiszuk]

It's time to rebuild my 700R4 (see sig below). I can afford a few weeks downtime this fall/early winter and decided to park the truck, pull the tranny and rebuild it.

I know the later 700R4's are "better" than the early ones and can be built stronger. My truck is used mostly as a daily driver to/from work and only occasionally to pull a trailer (usually a 16ft trihull boat or a trailer of contruction materials). There's no towing a 7,000lb camper through the mountains or anything like that.

Am I okay to rebuild my current tranny or would I be far better off finding a newer core? I've been searching junkyards and online but haven't found anything reasonable yet.

[Robyn]

A 89 "K" Case is the idea unit to build
Be sure to include the updated aftermarket input drum with the reenforced hub. Also replace the sun shell with a heavy duty after market one "The Beast" is one example'
Replace the roller clutch and the sprague units with heavy duty ones.
The clutch packs need to be updated to include a 9 clutch 3-4 pack and any other upgrades that are available. Always use colene steels in this box.
The 2-4 band servo needs to be updated to the corvette servo or better.
The front pump should be the 13 vane unit
Replace the front pump bushing and seal as a matter of fact.
Use a heavy duty "red" 2-4 band
Be sure to soak all frictions including the band for at least 1/2 hour in tranny fluid prior to assembly. Once the material is soaked fully its good to go.
Replace the thrust wahers with the best you can get. Many are select fit and many are plastic. If you can get brass or babit over brass its better.
Some sets come as stock and are plastic and will work ok
Be sure you use the proper governor with whatever you build. The Gasser units use a different one than diesel.
Get a Transgo 2-3 shift kit and follow the instructions to the letter.
Do not set the 1-2 shift on Kill as the shift is reeeeeeeeeeeealy harsh. Stay slightly lighter on the 1-2 setting.
There are many mods to do to make this box reliable but once you get there its a sweetheart.
A fresh converter for the diesel application.
You will need some special tools but they can be improvised.
The critical one is the seal installers for the input drum assembly.
Be sure your TV cable is in good shape, if not toss it and get a new one.
Be very careful on TV cable set up. This will make or break your rebuild.
Prefill the converter with 3-4 quarts of fluid prior to fitting it to the box.
Add 5 quarts of oil to the pan then start and fill with tranny in N untill up to the add mark all the while cycling through the ranges R-1 TO FILL ALL PASSAGES.
Once warm bring up to full mark and not over.
Keep us posted
any questions just ask.
Robyn

[bmiszuk]

Thanks Robyn, you need to make a sticky of that info!

My question is this.. I can't find an 89 K case. How terrible is it to use my 83 again? Is the difference significant?

[Robyn]

DONE made the whole post a sticky :0)

[JeepSJ]

Thanks Robyn, you need to make a sticky of that info!

My question is this.. I can't find an 89 K case. How terrible is it to use my 83 again? Is the difference significant?

The K case is heavier. They are easy to identify as there is a big K cast into the bellhousing. The difference is significant. It should not be hard to find one - just about any late-80's Chevy/GM truck with a big block or diesel should have one. I have seen lots of them in wrecking yards. When I bought my trans, I was able to order it with the K case.

[Robyn]

Yes you definately want a K case for your build.
The early trannies have several issues that you dont want to deal with.
I got a complete off ebay for my project.
While you are looking you can be gathering the other goodies.
Fresh converter
13 Vane front pump
Bushings and thrust washers
Gasket and seal kit
Transgo 2-3 shift kit
HD input drum
HD sun shell
2-4 band
Corvette 2-4 servo assembly
HD sprague
HD roller clutch
HD 3-4 clutch pack ( many outfits sell a package)
All the rest of the clutches can be of stock configuration.
Now be sure you get a V8 or diesel Tranny and not a V6 one.
The clutch packs and such are different.
I suggest doing it peace meal because otherwise you will have extra parts left over.
The tranny supply houses can do it this way for you.
Or you can buy a long overhaul kit with everything in one box and then add the special HD parts.
Once you get your goodies and before you do anything read the manual that comes with the Transgo kit.
Dont let a salesman sell you the small SK kit You want the 2-3 KIT (Big Box)
read that material untill you have it in your mind, untill you have the pages worn dog eared. The read it some more. The steps in the installation of the kit are critical and must be followed carefully.
When you have the box built then do the valve body on a clean clutter free bench. Dont use "red rags" around the tranny, use paper shop towels.
There are holes to drill, springs to change and all sorts of recomendations for the ON THE BENCH fix as opposed to in the rig.
These guys got it together and when its done the 700 will delight you every time it kicks you in the butt with a nice crisp shift.
DONT USE THE HYDRAULIC ONLY LOCKUP FEATURE.
Retain your electric lockup control.
Depending on what tranny you end up with youmay need to change the lockup solenoid to match your needs.
Or you can place control on a switch and let the tranny do the lockup with the valve body and shut the thing off around town via the switch.
If you find that your valve body does not have a lockup valve set in it we will cover that if and when it happens. ( some 700R4 boxes in the late 89 early 90 had electrical lockup only via the computer)
88-89 boxes were mostly valve shifted converter clutch)

OH if you find a 2WD model thats ok just change the ouput shaft to 4WD one.
You may get a better deal too. Also depending on what you get you MUST match the governor to the diesel. A gasser governor will shift it real goofy.
Get a diesel governor if you need one from the Chevy store.

Keep us posted

Robyn

[john8662]

Driveshaft length 2WD vs 4WD.

You wouldn't think this was an issue but...

I recently used a K case for a 2WD application and had the trans built with the longer center shaft and 2WD tailshaft for my application.

The trans is actually 1" shorter than my original 2WD 700 was in total length.

Odd huh?

Going the other way isn't going to work either, the case will be drilled and tapped for the 4WD dust shield (alum cover) and the 2WD just uses pressed steel dust shield with small fasteners.

4WD application, use 4WD case, period.

2WD application, you can go either way, just note differences.

J

[spitfirenut]

Is the K case a 4WD case as in K20, K1500 etc? or just a marking on the case? Judging from John's post the 4WD trans will fit in a 2WD truck with the right tailhousing. Trying to understand before I hit the boneyards.

[DmaxMaverick]

Is the K case a 4WD case as in K20, K1500 etc? or just a marking on the case? Judging from John's post the 4WD trans will fit in a 2WD truck with the right tailhousing. Trying to understand before I hit the boneyards.

Yes. Yes. And yes.

[Robyn]

The K case is just beefier and a better platform to build a good tranny on.
You can mix and match almost any combination of innards though.
I would recommend that you stay with the heavy duty diesel parts all the way through.

The K also has the dual valve bodies.

There is no mistaking a K case as it has a big K cast into the bell housing on the side.

If you dont need the big cast aluminum lower cover you can position and drill some holes for the stamped steel unit.
I would use the aluminum cover though as it will bolt right up.

Good luck

Robyn

[spitfirenut]

Thanks, that's what I need to know.

[6.5TDTahoe]

Requires 2WD out put shaft & extension housing!