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.

[Robyn]

Good luck on your search for parts.
If you have any questions along the way just ask.

The 700 although not a difficult box to rebuild can present some challenges. There are a couple special tools that are a "MUST HAVE" to be able to assemble the clutch pistons.
These are the seal installer tools. Without them its a no go and you simply can't assemble without damaging the seals.

I made mine here in the shop. You can do the same or possibly borrow a set.
The cost to purchase was not inviting for a single unit rebuild.

Good luck
Robyn

[78Chev]

I have a Bowtie 700r4 in my 2WD. Very solid and works as advertised (even though I had to put a transgo kit in it to make it shift right). The trans locks up in OD automatically (it has a NO switch in the OD valve train) but with a toggle I can bypass the OD valve body switch and lock it up in any gear (including 2nd). Since the converter solenoid is what controls lockup exclusively, anytime the OD VB switch is bypassed the thing will lock the converter (except in 1st). The VB only has a port for a switch in the OD train. I would like to have more control over which gear I can lock/unlock it and also have some protection with a pulse switch so that the converter unlocks as it shifts gears. As it is if I have the manual lockup switch activated and it downshifts from 4th to 3rd it jars the tranny when under load and so I'm afraid of damaging it. Also, the decrease in RPM from 3rd unlocked to OD locked is huge, so being able to run in locked 3rd then unlocking as it shifts into OD locked would make for smoother running on the highway.

I have the VB switches that I need and can figure out the wiring harness. Can I drill and tap ports for these switches in the VB? What would be involved in changing the bushings and valve trains? Or should I look for a VB with these ports already there? If so what would I ask for (e.g., year; model)? Thanks for your ideas. --Randy

[Robyn]

You need to inbstall a 4-3 pulse switch in the VB.
Most VB will have the ports in them. Dont dril and tap these as you can make a mess of things.
Look in the ATRA tranny book for the 700 and cruise through all the diiferent wiring styles and pick the one you like.

The late 80's VB will have the valving in it so it will lock the converter hydraulically and the only need for the switch would be to shut off the lockup for town driving.
If your VB has the ports you can install the valves and make it all work.

Good luck

Robyn

[More Power]

I was told by my trans guy back in the 90's that the pre-87 700R4 can be built/modified to shift without any electrical control. In fact, that's what he built for my 6.2TD GMC. The TV cable was retained, but not electrics. Shift scheduling was controlled by the TV cable, speed and hydraulic pressure internally. Worked great...

Jim

[mhagie]

I also have a Bowtie 700R4 and I have noticed that it will also go direct from 3rd to OD and lockup together,however that occurs at light throttle if I am applying more throttle than normal it will do the 3-4 shift and then T/C lockup.
Down shifting has been no issue as lockup drops out around 35-40 mph.
I do have the optional 3rd gear lockup switch but rarely use it.
Merle

[Robyn]

Transgo sells a kit to allow a non electric lockup.

The Valve body must have the lockup control spools in the bore sot do this though.

Some of the 700R4 boxes have the bores but are fitted with aluminum plugs.
The plugs can be removed and the spools, springs and such then fitted.

Ther is also a solenoid that is hooked up along with the hydraulics to give an electrical control too.

The early setup placed a check ball under the solenoid valve and this allowed the shift valves (spools) to do all the work.
This was however a tad hinky in the way it worked.

The new setup allows much better control of the lockup in and out.


best

Robyn

[6.5TDTahoe]

Requires 2WD out put shaft & extension housing!

[Robyn]

That is correct.

The case is the same but, the output shaft and tail housing must come from a 2 wheel drive application.

Pretty much the same rule applies to the TH 400, the TH 350 and the 4L80.

Robyn

[tomtaylor]

Hey Robyn, or anyone that would like to comment,

I have picked up 700R4/208 package from a 90 suburban 350 4x4. I was told by a trans shop that I would need 2 things for my rebuild. 1st was the computer from the suburban becuase it was controled by that. 2nd was that I would need a new stator for the 13 v-pump? So I have been reading alot about building these things on several sites and I found that Bowtie Overdrives offers a wiring kit for the 4 pin plug/solenoid and pressure switch inside the trans for the lockup that includes towing circuit/switch. Bowtie states that you absolutely do not need a computer to operate one of these trans.

Wherever I read I seem to get different detailed descriptions of little things to do to make this 700 work reliably. I am putting it behind my 6.2 so I don't need a monster I just need reliable and I would like to be able to tow without worrying about it. Have read about lots of people online here that had them well built and had no problems even when towing. Would love to hear anyones opinion about the best thing and the worst thing to do with these. Does everyone use 1200 stall converter on these?

Thanks for any detailed thoughts you all have.

[DmaxMaverick]

You do not need a computer to control the 700. It wouldn't know what to do with it. On emission controlled vehicles, the vehicle's computer ONLY controlled TCC (torque converter control), which is only an on/off function. This can be easily configured for automatic or auto/manual function.

You will not need the updated pump. The 1990 model should already have it. You will need the Diesel spec governor. You should use the low stall TC, but it is not absolutely necessary. I recommend it, but I know of a bunch of them that are using a gasser TC. With the higher stall converter, you will give up a lot of the low RPM torque, economy will suffer a little (all that fuel to wind it up is not needed to get going), your "effective operating range" will be reduced, as the redline on the Diesel comes in a lot quicker, and if towing, it will generate a lot more heat at lower speeds. If all you are using it for is a high-geared grocery-getter, the gasser TC may be fine.

The Trans-Go shift kit is HIGHLY recommended, as a starting point. If you have the thing scattered on the bench, you might as well add in some other "near bullet proof" hard parts. Otherwise, drive it sanely and save up or collect the parts along the way. Don't be fooled by the "I'm only running it behind a 6.2L so I don't need much" idea. Many times more 700's have been killed behind a 6.2L Diesel than much higher production, high-performance SBC's.

[tomtaylor]

You will not need the updated pump. The 1990 model should already have it.

Hi thanks for the info, since my trans is 21+ years old and and unknown history and miles shouldn't I just replace the pump with the rebuild? Or can it be tested it to see if it's good as is?

[DmaxMaverick]

The pumps were never a "problem", and rarely fail on their own. The later pump inserts (the "vanes" part) are only higher volume. You cannot "test" the pump independently, as they are integrated. They work, or they don't, with not much of anything in between. The 1990 700R4 was as good as they got, from production. The only place to go is into aftermarket hard parts, and the Trans-Go shift kit. The shift kit can be installed easily (valve body removal), but the hard parts require disassembly. If the tranny is otherwise healthy, I'd suggest only the shift kit, for now. Once installed and properly adjusted, you'll know what more may be needed. Unfortunately, that's the only way to know, short of complete disassembly.

[Robyn]

As maverick mentioned, the computer only controls the ON OFF function of the TCC

Now, this said the fellow at the tranny shop is partially correct. The late 700's (after about 88) do not have hydraulic shift valves for the TCC in the Valve body and they do the entire operation of the TCC with a solenoid valve run by the computer.

The earlier Valve bodies have actual valves in the VB that do the work and the solenoid was the final link to engage or disengage the TCC.

The 1990 model should have the valve bores in the VB and if so will accept the valve assemblies. (The bores have aluminum plugs that can be replaced with the valves)

If the VB does not have the bores, simply replace the VB with an 87 model that does have the bores

Transgo makes a great kit (700LU) or something like that to run the TCC totally with hydraulics and it can be tailored to lock up at the desired speed. NO WIRES. Its a great KIT

The governor must be used for the diesel (lower RPM shift speeds)

The pump changes were to increase oil flow volume.

The early pumps were also somewhat noisy.

Oil flow was the big issue though.

The other biggy is to get the Sun shell upgrade (Its called "The Beast")
The 2-4 band is also a needed upgrade (HD or better) they make kevlar, which is really good.

The 2-4 servo needs attention too. The 3-4 clutch pack must be upgraded with more clutches.

Upgrade the front sprag and the rear roller lock. (They are small and can break)

The little 6.2 will literally shake these things apart, so dont think, as Maverick mentioned that "its just a 6.2" The little 350 MOUSE motors are real easy on a tranny in comparison.

Have fun and good luck.

Missy

[Edahall]

If it has not already been mentioned, I would look into buying a torque converter than has been opened and had all of the veins welded. There are some other high failure items in the torque converter that can be strengthened as well. That said, my dad had 3 transmissions that were completely wiped out due to the torque converter coming apart and sending steel shavings through an otherwise good transmission.

[tomtaylor]

Really good to be here and get such great direction from everyone. Thanks for the great details I will use it all for my 700 rebuild!!!!!