700R4 Trans

[Ryan Colley]

Looking for some advice on my tranny...at highway speeds with engine warm it seems to slip in and out of overdrive (possibly TC locking/unlocking???) in short 2-5 sec. intervals. In order to get it back to normal I have to either back off the throttle or give it a quick shot to get it to calm down. Tranny also lugs bad in OD when getting back up to highway speeds after slowing down.
Checked fluid, previous owner had approx. 1 litre too much fluid in the tranny. Removed the excess plus a little more and replaced with Lucas anti-slip additive. No change to previous problems.
Truck has just under 200,000 kms and has had some tranny work done (according to previous owner...)

Any advice, or is this a 700R4 problem I should just "live" with.
Thanks

[ZZ]

I had my '90 GMC 4X4 with the 700R4 rebuilt in Dec 03. The had to do a warranty rebuild in July after it burned up.

I have this same problem as you at highway speeds. Around town, my OD, torque operates & locks up as it should. It doesn't seem to be a heat issue, but more of a pressure thing. After at least a 10 mile highway run; it will go in & out of OD between 35 - 45. I also don't feel the TC lockup until after it sits awhile. I've took it back to the tranny shop 3 or 4 times and they can't pin point the problem. They will only drive it here in town and then it is normal. They say they don't have time to take it out of town to see the problem. They claim to have put a heavy duty low stall torque in it that is supposed to only a 200 rpm drop when locked and they say that I don't feel the lockup after a highway run.

I decided a couple of months ago that I will have to live with it. The 1 yr warranty expires in about a week. I put a cooler on it and a temp gauge on it to watch the operating temps. I very seldom goes over 110 - 120 at 70 mph if is a real warm day. It stayed under 100 degrees on a recent trip with temps in the 30's. Evidently, it much be locking and I don't feel it

[john8662]

I think your problem lies in either a bad throttle position sensor or the sensor needs to be properly adjusted if the torque convertor has "busy shifting". I had a 90 model 6.2 suburban that had problems keeping the torque convertor locked. It acted like this for a long time, I never figured it out. I blew the transmission at 195k miles (bought it at 180k) and had a reman installed, but before the install, suspicious of the throttle position sensor, installed a new one. Evidently the sensor/switch was bad, because the reman transmission torque convertor worked fine. The old throttle position sensor I took off was "sticking" so that was my problem all-along. I probably could have gotten more miles out of the tranny, if i had known that before hand.

[ZZ]

I don't know if you responded to me or Ryan, but on mine the tranny shop checked codes and found 3 bad sensors. So, I asked him to by-pass all of it. It now has a direct ground and is still switched through the brake light switch. So, I think this eliminates the sensors & etc. I re-adjusted the TCC but the erratic shifting moved up from between 33-40 mph now to 38-45 or so. It would seem with the low temps it runs at on the highway that it is holding in OD and the TC is locking. I just take it a day and/or a trip at a time.

[Ryan Colley]

Thanks guys for the info. I did a test this morning on the way into work, left the tranny in "D" for roughly 20 mins before shifting into OD. Didn't notice any of the slipping/hunting problems as in my original post. This leads me to believe it is either temp. or pressure related. I don't know much about the throttle position sensor - how do I locate it and/or test its operation??? Thanks again.

[Subzilla]

TPS is attached to the injector pump and it is adjustable. Not sure how to check it. Good luck. I wish I had the time and money to convert my Sub to a manual tranny.

[ZZ]

My 700R4 started biting the dust today. After driving about 20 miles from home running 65 /w cruise it dropped out of overdrive to 3rd. I babied it another 9 miles to my Doctor's office. It sat long enough to cool and then it did the same thing coming home.

The warranty on the rebuild expired last month, but the tranny shop is going to honor it for this since this is the third failure since they rebuilt it in Dec of 03. I take it back in this coming Monday.

He talked like he may change out the whole thing. I screwed up the 1st time and let my original unit get away. They rebuilt a different one for me so that it would only be in the shop for 1 day for the swap.

[shamanie]

I'm just utterly baffled. I have a 700r4, well had, I think it's smoked now, but my truck, an 83 blazer has D321 displayed. Do you guys have a differnt display up by the instrument cluster? It seems that the original transmission was a th400. So when does OD take place? What dictates when the tranny goes into OD? Is the 700r4 a 3 speed w/OD? Or is it a 4 speed with OD?

I had a horrible time in D on the highway, as it would go into and out of OD and constantly want to downshift into 3rd. I go up to 15mph in first, 30-35mph in second, and would have to keep it their going about seventy, because forth gear would just loose speed until I had to downshift, oyve. OD obviously doesn't engage in first and second, at least I think, does OD engage in third? Anyway, That problem seemed to be alleviated by the addition of a turbo. I could cruise in D with 3lbs of boost, and around 900 to 1050F egt's, comfortably but that is not the case anymore. I was on the freeway and in 3rd it would just rev to all hell with no power. I had second gear and got it to my shop. It was like 3rd was neutral.

Anyway, I'm hoping that a new tranny, as this one was only 25K-30K old and reman., will be a different experience. I'm going to buy one from Level 10. They have a stage 2 700r4 that's beefed up and "bulletproof" whatever the hell that means.

Thanks for your patience and sorry for my ignorance.

[Robyn]

Ryan
The 700 R4 is a very fussy tranny to say the least.
To totally fix the problems you really need to install a Transgo 700G shift kit. Now I am not stumping for transgo but their stuff works and works well. I have used their products for many years and recommend it to anyone for any box with problems.
You may also have a switch problem in the valve body switches. depending on what setup is there.
If one of the pressure switches on the valve body is having a bad day when it gets hot you are going to have eratic behavior. I Recently rebuilt an 88 700R K case for my Hummer replica project and I placed a 5/16 check ball in the snout of the LTC solenoid. This runs the LTC with only the valves in the valve body. You must be sure you have a set of valves in there as some models had aluminum plugs in the valve bores and ran the LTC with the computer.
But to fully realise the best from a 700 you need to do the transgo kit thing. Its not hard to do if you just follow the instructions one step at a time. Drain the pan and let it set for several hours with the filter off. Removing the valve body needs some care as there are several check balls in there. Not to worry just as long as you coral the little buggers. The kit will tell you where to put them back and which ones to leave out.
Some none graphite wheel bearing grease works fine to hold the little suckers where you want them upon reassembly.
If you do the kit as described you will be amazed at how the 700 works. Mine is an absolute terror now. Dont try to second guess the instructions and if given a choice be honest and follow the recomendations for the application. DONT set it up for FULL RACE for your daily driver cause its going to be brutal. Just go middle of the road and it will be wonderful.

[Robyn]

There is also a temp switch in some models. It is a round silver little fellow that is bolted to the back end of the valve body and has to conectors on it. If this guy takes a **** you can get intermitent lockup, no lockup or variations.
The 4th gear (OD) not working is controled by the valve body and is a result of the 2-4 band. Also there could be a problem in the servo assembly which is on the side of the tranny toward the front.
This servo has a compound set of pistons in it that runs second gear and 4th (OD) if there is a seal problem things get goofy. Also if second gear is getting real soft and taking a long time to slide in its a good bet the 2-4 band is toast.
The shift kit makes some serious recomendations as to what pistons to use in what applications.
Not to call trash on any one tranny shop but far too many tranny techs dont have a clue how to keep a 700 alive and working good. This box will kick your butt big time if things are not right.
TV is very critical on this box. The cable is not just passing gear but serves to tell the box what the throttle position is and how much demand is on the engine as there is no vacuum modulator.
When the throttle is wide open the TV cable should be maxed out. On a stock diesel it is easy to do. The adjustment is at the back of the engine.
press the little cable release button on the end that goes in the bracket and slide the little ratchet slider all the way toward the firewall and then mash the throttle to the mat. The cable should adjust itself properly. The way to tell is to go for a low speed light throttle 1-2 shift on flat ground. As soon as the tranny makes the 1-2 shift, stomp it. You should get a 2-1 downshift. If you dont you need more TV pressure which means the cable needs to be adjusted longer.
The 700 will go away if you try to run with to little TV pressure.

[Robyn]

To Shamanie
Sorry to hear of your 700 troubles.
The 700 is a 4 speed tranny. The 4th gear is Overdrive. The indicator can have one several indicators D with a circle around it is OD and will shift from 1-4 the D position will shift 1-3 and then 2 and 1
The lockup can happen in 2-4 only and will not happen in 1st.
Depending on how the box is wired you can have lockup in 2-4 3-4 or 4th only and the calibration of things (valve body or computer will control the LTV engagement speed).
When the tranny is working properly you will feel the 1-2 shift the 2-3 shift and the 3-4 shift. If the LTC has been messed with (recalibrated) the lockup can occur right after the 1-2 shift and stay locked through 4th gear.
I prefer to install a manual switch to shut off power to the LTC so it can be turned off around town. You need to run lockup at highway speed though as running 4th without lockup can result in too much heat buildup. Hope this helps.
RC

[shamanie]

Robyn,

Really appreciate your input on this thread as it is quite evident you have extensive experience with this tranny. Much appreciated.

I'm all go on the transgo kit and as soon as I hear back from the shop I'll order it.

I don't know what to look for as I have only ever driven my rig but it seems like I don't feel any difference in the transmission until 4th. It shifts and then I get a drop in rpm's.

Hopefully everything will work out. I'll keep the thread active with my updates as they progress. As long as that's ok with the original poster?

[Robyn]

Another thing to think about.
If the box is coming out of the truck and to be taken apart here are some real important things to do.
Have the tech install a "TORQUE DRIVE' assembly
this includes a special hardened input shaft with an updated input drum. This package also comes with a reenforced sun shell and a special sprag race and a torrington bearing that replaces a plastic thrust washer. The sun shell is the weak link in this tranny followed closely by the input drum. As this is in a 4X4 its almost a given that one of these parts are going to fail and it wont be in your driveway when it does. This upgrade is not cheap but just rebuilding this tranny is not the answer to get rid of its problems. Also it would be a great idea to replace the front pump with a 13 vane unit. when the pump is apart the drain back hole from the front seal area is also a problem and if not opened up as is described in the kit can cause seal failure or blowout do to oil presure buildup due to the hole being too small. A kevlar 2-4 band is a real plus too.
Be sure and dont go crazy on the 1-2 shift programing. Dont use a corvette servo for 2nd gear its toooooooooo brutal with all the other mods that the kit makes. It wont hurt anything but it will kick you hard everytime it hits 2nd gear. If this tranny has any metal or junk in the pan be sure and replace the convertor with a heavy duty one and always flush out the cooler lines and **** ALWAYS PUT AN INLINE TRANNY FILTER IN TH RETURN LINE**** If you dont do this you will eat your new $$$$$$ tranny in a short.
I have never had a real love affair with the 700 but it does have some nice advantages if you build it right. Its got to be clean and its got to be calibrated right. If your tech does not agree with what Im telling you do yourself a favor and find another tranny guy unless $$$$$ is something you have to burn. The 700 will fail again and again if its not done right and the stuff I am telling you is the only fix that I have ever seen that works on these little beasties. Hope this helps out. Also if your tranny is not an 87 or newer with a 30 spline input shaft toss the thing and find an 87-90 and rebuild it. The early ones had a 27 spline and will self destruct in a 4X4 in time. Not if its when. The only other thing to remember in the 700 is to be sure that it has a Convertor clutch valve assembly in the valve body. Many of the later ones had a set of aluminum plugs in the TCC valve bore. These can be replaced witha valve set from an earlier 700. some trannies also did not have the TCC valve bore. Stick with an 87-88 model box and you will be fine. If you want you can set this critter up so you can run the lockup fully electric or you can wire in a switch to put power to the clutch when you want on the highway. Or you can follow the kit instructions and set it up so the hydraulics will run the whole shooting match. I prefer to wire it up with a type two(2) wiring diagram and then you can just turn the power on and let it do its thing or shut it off around town or anytime the thing is hunting. ( locking and unlocking quickly like around town)
If you have a gas rig with a computer control on the lockup its not a problem you can run it just as the factory had it setup if you like. Just swap all the internal switches from your original box to the new one (If you use a different box) also be sure that all the switches are working properly as having one of these not working right can drive you nuts with problems and goofy little things going on.
I hope this helps you. I spent many hours researching this stuff before I did the last 700.
When working right they are a sweety and when they arn't they are a !@#$%^ :0)
good luck
Robyn

[Robyn]

One thing to keep in mind with these older rigs.
Unless "you" are the original owner and know the complete history of the truck there is absolutely no way to know for sure if what you have is the way it began life.
It was mentioned earlier about the shift indicator being D321 well they made a bunch if different stuff duriong the many years of production.
Early Blazers and 1/2 tonners had turbo 350 trannies in 1982 the 700R4 came on the scene and was used in the 1/2 ton and Blazers as well as light duty Subs. The 1/2 tonners and Blazers were not fitted with TH400's Many can be found there as the aftermarket can fit almost anything into anything else. During the early years if you had big power in your Blazer a 400 was the only way to fly. I ran across an 84 Blazer the other day with a Vortec 454 in it and a 4L80E tranny and its mating trans case. Real sweet swap looked to be factory as it was very clean install. Just try hard to think things through and be sure the combination you have will work right. So many shops just toss stuff together and hope it works.
The wrong combination s will wreak havoc on your wallet and your patience.
**** Never try and use a tranny from a L4 or V6 up behind your strong mouse or big rat thumper its just not gonna happen.
The L4 and V6 boxes have too few clutches and will never hold the power.
Ask many questions and if you dont get matching answers from several techs Fall back 30 and regoup.
This is not rocket science its just some very basic common sense that has to be used to make life run smooth. There are no little gimics that will fix these trannies without some serious $$$ and some time. Just bite the bullet and do it right or do it over and over and over.
Seen it all and its cost many good folks a lot of lost $$$$$$ and lost sleep.
best to ya
RC

[Ryan Colley]

Thanks for the posts RobynC52...very interesting and informative reading. I will also look into the transgo kit. Any recommendations on where to find one (that will ship to Canada without major fuss???).

Shamanie - no problem continuing this thread, I will be watching with interest.

Thanks guys,

Ryan

[Robyn]

Ryan
I would think you could get them through your local parts disributor or auto parts store.
if not look up transgo on the web and order direct from them.

[Robyn]

Here is an ebay listing that is a buy it now.
This is the kit I used in the last 700 I built and it works super.Item number: 7946859146
if you cant find one locally give this a shot.
Ebay is my favorite place to find things.

[Ryan Colley]

thanks I'll check it out...

[Fumes]

I have a 85 GMC Van, and I rebuild the tranny when, I changed motors. I rebuild it myself with the help of the Service Manual, some 700R4 books and video I picked up at JC Whitney.

I also put the Transgo kit in, and it works great. After a certain speed the converter stays locked up. This is great when pulling a trailer as it keeps the tranny running cooler.

I didn't add filter, but this probably a good idea. What brand did you put in - Robyn C52?

[Robyn]

Fumes
there are several types availablem from themparts houses or tranny supply shops. What works real well is to put in a remote spin on unit and run the return line through it. You can then toss the filter every 5-10 K miles and this really helps keep the junk out of the tranny. Auto tranny's by their nature make crud even when there is nothing going sour. The small inline units are made by several treans parts suppliers. Just ask your parts man for an inline auto tranny filter and he will know what you want. The come to fit either 5/16 or 3/8 line. you can just unhook the retyrn line from the cooler and stuff the hose over the flared end and clamp it and put the other end onto a pushlock fitting that will screw into the cooler. ( Or if you are using a cooler that has only push ons your set)
KEEP EM CLEAN AND COOL AND THEY WILL LIVE
Another new twist I am seeing done is the local guys are having a super heavy duty NON lockup convertor built for the 700. This requires changing a valve in the trans to feed the oil right but I am hearing that this really makes the 700 head and shoulders more durable. The non lockup convertor they are building is using the large Ford Drive and driven turbines and this greatly improves the ability to transfer power without all the heat buildup. With the lockup plate inside the 700 convertor has much smaller turbines and generates far more heat.
I am going to put one of these in my Hummer replica I am building. I have a fresh 700 in it now andthe lockup is a pain. I have it on an on off switch so I can shut it off around town and run it at highway speed. The thing is anoying around town as mine will lock as soon as it hits second gear. I can fool with the calibration but even at best the lockup is marginal in any heavy application

[farmerherb]

Guys, I have 5 so called rebuilds on one 700r4. The original trans. went 147,000 miles, every rebuild not more than 70,000. I have a 4l80E in my 95 K2500 with 302,000 miles. Transmission shop mainly repair not rebuild transmissions. I rebuilt my own 700R4 with all the heavy duty parts($300 worth)besides the rebuild kit. There is a 2-4th gear servo you can install outside the transmission that they say you can tow in fourth gear. It is huge compared to even the corvette servo everyone sells. But its pricey 57.00.

[dieselbegreat]

I have an extra corvette servo kit for a 700R4 if you are interested, which is supposed to make the upper gears hold firmer.

If I may interject here, I think this is a good thread with very good info, BUT there is something I noticed in my quick reading that bothers me. Do I understand correctly that this 700 is a transplant for what was originally a 400? Does it correctly use a throttle valve cable setup or a vacuum setup? Beyond that, each vehicle and rear axle ratio had its own governor (located behind the round cover on the driver side) spring/weight calibrated combination to determine default shift points. I know from experience that if these things are not correct for the vehicle, it will probably drive very badly indeed.

[Robyn]

Farmer
Rebuilding a 700 can be tricky in that there is far too much bad information out there.
I have done my share of autos and have had zero problems with the 700 as of late.
Here is the tricks that work.
The basic rebuild is the easy part, just be careful to install the lip seals in the drums correctly and dont force them. Use the tools needed or a good improvisation. Be sure you have a tranny that was designed for the power you are using. V6 to V6 V8 to V8 and so on. The clutch packs are different.
Now comes the easy part. Buy a transgo 700G shift kit and follow the instructions to the letter. Also its a good plan to install a "Torque drive system" and the "Beast" sun shell Outside of this all you need is a good quality convertor and you are set. Also as was said earlier, the governor. The kit addresses this and its a piece of cake to change if need be.
Good luck
RC

[shamanie]

Well, I just got off the phone with Level ten and I'm looking at a $3000 transmission through them. They say it is as good as it gets with the 700r4. (Shrugs shoulders) They have 3524.00 with a 500 core that would be deducted once I get the 700r4 I have shipped back to them. I have to pay 350.00 round trip shipping. And then comes the install charge???????

Tciauto.com wants 2000 no core charge. I just emailed them to see if that includes a torque converter. I hate being so incredibly ignorant. I hate having my truck down.

Level ten wanted to know what transfer case I have? I have no friggin idea. 83 chevy blazer 4x4....Transfer Case?

I need your help here guys...this will indefinately break the bank.

What other altenatives do I have here?

[john8662]

shamanie,

I think DieselBoy needs to post here too, I seem to remember him going through several Bow-Tie Over drive 700 units until getting an Art Carr unit that worked and has stayed behind his turbo 6.2L. I need to build a new 700 as well for my 4x4 burb and probably in the near future my 86 truck.

For the transfer case, if it's stock it's an NP208 for an '83 that is. If in doubt, crawl underneath and there will be a 2" round red tag screwed to the back of the case near the tail shaft. Clean if off, it will have the model number on it.

[Stray Cat]

Avoid PATC (Performance Automotive Transmission Center) in Louisiana like the plague!!! They have a great web site that highlights their 700R4 products, "Raptor" and "Raptor Jr.", etc. After excessive thousands of dollars, excessive down-time, and multiple re-builds, I learned that their product is garbage! The story is long and sad; I don't have time to tell it all now. But, if I needed to to save someone else from the cost, frustration, and down-time, I will. PLEASE don't buy from these people...while the marketing is excellent, the product is poor!

[shamanie]

Consider PATC avoided stray cat. Thanks for the heads up.

[TimK]

Shamanie,

I would think for $3K you would be able to get a 4L80E and the standalone computer to run it. It seems to me to be a much stronger tranny the 700r4. Have you considered this?

TimK

[shamanie]

TimK, here is a breakdown of what I am looking at...

TCIauto.com

Part# 371403 Truck Master 700r4 for diesel =

1950.00

Part# 242821 Chevrolet/GMC 1984-91
TH700R4 w/Diesel and 1991 &
later 4L60E w/Diesel =

$381.62

No core charge, and shipping one way.

How does that sound? 2300+install(How much should this cost?)

The level ten kit, although perfectly capable, is just completely out of my price range..

So I'll get a new TC and a Tranny. Here is a description of the Truck Master 4x4 tranny from
tciauto.com

"Truck Master Transmissions

The Truck Master 4x4 transmissions bring performance to your four-wheel drive. A four-wheel drive application is especially tough on an automatic transmission and the addition of bigger tires makes the job even harder, We designed the Truck Master series to be as tough as your truck, because they are built with the best components available and programmed to provide crisp shifts time and time again."

[Dominique]

I am on the transmission Mission also and I came across this Item on Ebay 7948816551. This guy is a trans builder in Florida and after talking to him yesterday I'm going with the super heavy duty model that he has for $1195 shipped to my door and no core charge. He has other models avail too If that will help. I think $3000 is a bit pricy.

Dominique

[Robyn]

Do your own rebuild and do it by the book with a good transgo shift kit and you can have a killer 700 for under $500
These guys are fleecing the folk here they are.
This tranny stuff is not rocket science or brain surgery. Follow the GM book or one of several how to tranny books and do the transgo thing along with a new converter and an extra filter. Boom PloP DONE