Just figured out my truch has TH700R4 trans...

[Davidf]

Ok, so you might ask how did you not know. Well, I purchased the truck in March and have been concentrating on get it running right, good brakes, A/C, etc. The trans operated ok and only leaked slightly...so I did not pay much attention to it and assumed it was a TH350. Then, I drove the truck 350 miles in one day...mostly highway at 75mph indicated. Upon returning home, the leaking was worse and bad enough to warrant repair.

So, assuming a TH350 I purchased all external seals/gasket. I pulled the pan/filter and immediately thought to myself something seems odd. Sure enough, after a bit of online investigation, I discovered it is a TH700R4 (4L60). Dang or hurray, not sure which. I thought the TC cable was the TH350 kick down cable and always thought it odd that I did not have a vacuum line connected to the trans (i.e. modulator).

Anyway, the leaking issue is mostly from the pump to case seal (o-ring) Obviously not an easy fix. So, I was thinking of trying one of those stop leak products for automatics...something I never have done or even recommend. What do you think, might it work? I fear the o-ring might be broken and the stop leak won't work. Dang!

[leftybass209]

You shouldn't have said that, now you opened the door for piles of people to tell you how crucial your tv cable adjustment is and now your transmission will explode because you drove it way too far!

In all seriousness, those transmissions do run hot. I wouldn't waste my time with a stop leak. I know it's a pain to have a hard to get leak ( my 700r4 leaked everywhere but the front pump) but you do want to learn about that transmission so you can better keep yourself from getting stranded.

Check the numbers on the transmission and find out what year you have. An '88 or later trans is preferable because GM made several improvements, but an earlier trans isn't the end of the world. Also, drain it regardless and check what comes out of the pan, if the tv wasn't/isn't adjusted correctly, you'll get a lot of band material.

Next, post some pics of your throttle linkage. The tv setup is important to the longevity of the trans, but some people go overboard with how they try to get that point across, using scare tactics that driving even 5 miles will burn up your trans .

Bowtie Overdrives has a lot of great OD trans info. It's invaluable reading but beware, once you read their web page you'll feel like your transmission will spontaneously combust if you haven't purchased their products.

Best of luck!

[Bigdav160]

Most likely it's the pump/torque converter bushing and seal. The pump o-ring, in my experience, doesn't leak.

[michael bustamante]

" Bowtie Overdrives has a lot of great OD trans info. It's invaluable reading but beware, once you read their web page you'll feel like your transmission will spontaneously combust if you haven't purchased their products. "

too true!!!! im still debating driving my truck because of a spring they say i absolutly must replace
in all seriousness though i also highly recommend reading the info on this site

[Davidf]

Guys, I am not a newbie when comes to transmissions. I successfully rebuilt the ZF automatic in one of my BMW's. So, when I say the leak is coming from the pump to trans case o-ring, then that is where it is leaking...common or not.

Once I realized it was a 700R4, the first thing I did was check the TV cable. The bracket geometry is good. Rochester carb, cable connector is about 1" down and 1/2" back from throttle plate rod. Cable is mounted parallel to linkage connection point. The cable seemed a little slack at idle, so I readjusted for tight at WOT. I check the movement of the valve in the VB and I get full depression of the valve at WOT. The fluid was not burned and normal material on the magnet in the pan.

But, back to using stop leak products...I think I will give it a try. If it doesn't work, trans comes out. Then, I might figure out how to make the torque convert lockup function work.

Thanks for the link, Michael...will give the site a visit.

[Davidf]

I think I will just go ahead and drop the trans and fix the leak properly. Ugh, now I have two trans to drop ahead of me. my '04 BMW 545i is leaking from the front trans input seal as well.

[67ChevyRedneck]

I'd rather have a leaky 700R to fix than a leaky TH350! So, in that respect, you have a good problem to have!

I can't believe the seller didn't talk up the 700R, I would definitely spend a little more on a truck that was already set up with OD.

I think you're making the right decision... I personally believe that those "stop leak" products also plug up stuff they're not supposed to...

I too drink the Bowtie Overdrives Kool Aid. I used both their TVmadeEZ and brake switch lock up kits in my 700R about 9 years and about 35,000 miles ago. Still shifts as it did 9 years ago. I set up my first 700R wrong (was a young kid) and it lasted about 3-4K miles...

[michael bustamante]

when you drop the pan, make sure you get the filter out in one piece. sometimes, if i remember correctly, the tube that mounts the filter loses a piece inside the shaft and when you put in a new filter, the filter will prevent the pan from being reinstalled. double check that part where the filter tube installs when you install the new filter

[Davidf]

Yep, you are talking about the filter seal. It did indeed stay up inside the trans and was a bit tedious to dig out.

Been doing a bit of research on the 700R4 and connecting the lockup feature of the torque converter seems like a very simple process. Just needs power all the time except when the brake is depressed (so engine wont stall during panic stop). Only locks up in 4th gear.

[michael bustamante]

yup. i used a brake switch from a 92 chevy truck.

[VetteVet]

I like this website.

http://www.transmissioncenter.net/hi...FYsWHwodp6QKnA

[67ChevyRedneck]

Originally Posted by Davidf

Been doing a bit of research on the 700R4 and connecting the lockup feature of the torque converter seems like a very simple process. Just needs power all the time except when the brake is depressed (so engine wont stall during panic stop). Only locks up in 4th gear.

You've probably read my posts about that. Scared the crap out of me when the engine died and I lost pretty much all my braking power (PDB). I used to have a switch that just locked and unlocked the TC based on pressure or something (don't remember) but it sure as hell didn't work fast enough when you slammed on the brakes. I pulled it out and replaced it with the BTO one.

Using one out of a truck that came with a 700R is a great idea too.

[Davidf]

Update: Over the weekend, I dropped the transmission (very easy, took about 1.5 hours), replaced all seals, and reinstalled. While the trans was out, I tested the TC lock-up solenoid and could get no response when 12v applied. So, today I purchased a new solenoid to install prior buttoning up the pan.

It seems there was remains of the TC lock-up circuit evident but not complete. The wire had been cut. A dual circuit brake light switch is already present (wired to constant 12V????) along with a vacuum operated NO switch. So, I will wire accordingly: Switch 12v power through brake light switch, through vacuum switch to TC solenoid. Should work well, I hope.

[Taibo]

Originally Posted by leftybass209

You shouldn't have said that, now you opened the door for piles of people to tell you how crucial your tv cable adjustment is and now your transmission will explode because you drove it way too far!

In all seriousness, those transmissions do run hot. I wouldn't waste my time with a stop leak. I know it's a pain to have a hard to get leak ( my 700r4 leaked everywhere but the front pump) but you do want to learn about that transmission so you can better keep yourself from getting stranded.

Check the numbers on the transmission and find out what year you have. An '88 or later trans is preferable because GM made several improvements, but an earlier trans isn't the end of the world. Also, drain it regardless and check what comes out of the pan, if the tv wasn't/isn't adjusted correctly, you'll get a lot of band material.

Next, post some pics of your throttle linkage. The tv setup is important to the longevity of the trans, but some people go overboard with how they try to get that point across, using scare tactics that driving even 5 miles will burn up your trans .

Bowtie Overdrives has a lot of great OD trans info. It's invaluable reading but beware, once you read their web page you'll feel like your transmission will spontaneously combust if you haven't purchased their products.

Best of luck!

Yo, Lefty! TV cable, dude!

[Bigdav160]

The wire had been cut.

It could have a hydraulic lock up kit installed

[kyman]

And u can also make it lock up in 3rd, that's how I wired my 67. I just used relays and brake light switch. Can use a vacuum pod off of a mid 80's van or truck, but I didn't feel the need to.

[Davidf]

The TC lock-up solenoid was wired to a 4th gear (internal) pressure switch (ground wire). A (internal) pressure switch is installed in the 3rd gear pressure port, but not used. I don't care about 3rd gear lock-up anyway. There is no external hydraulic pressure switch mounted.

I tested the lock-up solenoid last night with compressed air and indeed works fine. It takes pressure to reset the plunger so that when 12v is applied it actually moves the plunger and makes noise. Otherwise, you can tell if it is working or not.

[Davidf]

Update: All new seals on the trans, reinstalled, filed with fluid and no more leaks! TC lock-up working and trans shifts are nice and crisp now that the TV cable is adjusted properly.