700R4 went out while towing. Culprit?

[OuchMyToe]

The TV cable needs to be right, close enough won’t get it done. Ideally the cable needs to be adjusted with a pressure gauge connected.

Unless you have a really stout 400 engine (500-600 hp) a 700 is just fine.

Drop the pan, I bet you find a bunch of crud in the pan. That’s the remains of the clutches and band.

When you rebuild the trans, install the raybestos Z pac, wide band, upgrades drive shell, updated input sprag, hardened pump rings, and a decent shift kit.

Once all that is done, make absolutely sure the TV cable is adjusted right. The line pressure needs to increase as soon as the throttle is increased.

BTW, the linkage on a old school carb for the kickdown linkage won’t work for a 700.
Read this, even though it says 2004R, the process is the same.

https://www.ckperformance.com/Files/112573/ThrottleArmTVarticle.pdf

Thank you!

 

[OuchMyToe]

My bet is the lockup was never plugged in or converted. Need a rebuild but like others say... Use all the upgrades and you will get plenty out of the 700. Big cooler! There is a small "breather" tube on top the trans. Run that down away from exhaust to prevent a fire if it ever over heats again.

Awesome point! I'll do it.

 

[OuchMyToe]

What size tires and what is the final gear ratio?

Stock tire size I think—can't remember off the top of my head and can't look 'cause I'm at work. Not sure about the final (OD) radio either. I agree that if it's got a custom high OD ratio, that could add to the issue.

 

[OuchMyToe]

As long as the trans isn’t constantly shifting/downshifting between 3-4, the converter doesn’t skip, and the engine doesn’t lug, you can tow in overdrive. The “don’t tow in overdrive” rule of thumb came about because the weezing engines of the early 80s barely had the power to pull the truck unloaded, put any weight behind the truck and the nonstop shuttle shift overheated the trans.

The 3-4 clutch has been a issue with the 700 since day one. The trans originally had 5 clutches, then later in its production run they made engineering changes to fit 6, when the 4L70 came out they upgraded to 7. The problem with adding more frictions in the same space requires thinner clutches/steels. The thinner parts don’t handle heat nearly as well. They warp, burn, glaze, once that happens it’s all downhill

The ultimate fix is the Raybestos Z Pak, it uses 12 single sided frictions. The 12 thick single sides frictions offer more surface area, and radiate heat better than thinner clutches

As long as the trans isn’t constantly shifting/downshifting between 3-4, the converter doesn’t skip, and the engine doesn’t lug, you can tow in overdrive. The “don’t tow in overdrive” rule of thumb came about because the weezing engines of the early 80s barely had the power to pull the truck unloaded, put any weight behind the truck and the nonstop shuttle shift overheated the trans.

The 3-4 clutch has been a issue with the 700 since day one. The trans originally had 5 clutches, then later in its production run they made engineering changes to fit 6, when the 4L70 came out they upgraded to 7. The problem with adding more frictions in the same space requires thinner clutches/steels. The thinner parts don’t handle heat nearly as well. They warp, burn, glaze, once that happens it’s all downhill

The ultimate fix is the Raybestos Z Pak, it uses 12 single sided frictions. The 12 thick single sides frictions offer more surface area, and radiate heat better than thinner clutches

Great information—what I like to learn. Thanks.

 

[HotRodPC]

Culprit was overheat, foamed the fluid and puked it out the breather tube most likely and burnt up the forward and/or direct clutch pack(s). Heat Is #1 killer on transmissions. Some tolerate it better than others and handle some abuse, but 700r4 isn't one of those. Have a factory radiator cooler is NOT enough if you're towing or putting a strain on it. ADD, and I say ADD a cooler, don't bypass the radiator cooler to replace it with a bigger cooler, ADD a cooler to the radiator cooler. You also need the radiator for warming the fluid in colder climates of colder months.

 

[shiftpro]

Culprit was overheat, foamed the fluid and puked it out the breather tube most likely and burnt up the forward and/or direct clutch pack(s). Heat Is #1 killer on transmissions. Some tolerate it better than others and handle some abuse, but 700r4 isn't one of those. Have a factory radiator cooler is NOT enough if you're towing or putting a strain on it. ADD, and I say ADD a cooler, don't bypass the radiator cooler to replace it with a bigger cooler, ADD a cooler to the radiator cooler. You also need the radiator for warming the fluid in colder climates of colder months.

You nailed it BossRod.
Once the oil starts bubbling out the dipstick the damage is done. Even a temp gauge... once it shows HOT!!! it's too late. If you watch it closely, and see it beginninging rise then it's time to shut it down.

 

[Itali83]

What is “too hot” temp wise? My temp sensor is in the line directly out of the trans so my theory is it’s the hottest point the oil is in the system. I put 400 hard highway miles on the old girl yesterday. Not towing but it was 90 out, I was running 80mph+ and had a steady 200 degree. Towards the end of the trip, it was creeping up to 210-215.
If the converter unlocked it would spike to 250 but come right back once locked.

my trans is funky. I did a half ass rebuild 8 years ago and it’s been this way from day one so I just run it still.

Ben

 

[HotRodPC]

I'd say you like it around 200 or lower if you can get it. Expect up to 220 with a strain or climbing a small grade But I'd say 250 for sure is HOT and killing it.

 

[Matt69olds]

The best place to monitor temp is the pan. That’s the best place to get a good average temp. Don’t use the line pressure tap, there is zero fluid flow, you will be basically reading the temperature of the case. The cooler line out of the trans to the radiator will be the hottest fluid, that’s basically the fluid coming out of the torque converter.


I wouldn’t worry until the temp gets over 230-240 continuously. It might get that hot if your really working the truck, but ideally it will cool back down once you start moving and the converter locks. Obviously, the lower the temp (within reason) the better.

Adding a big cooler is always a good idea. If you drive the truck in cold climates, keeping the radiator cooler is a good idea. That prevents the fluid from getting too cool.

 

[Dave M]

LOL! Yes. Yes I have. There's the stock transmission lines running to and from the radiator. Because of the all the tweaks I had to make, it's got a somewhat upgraded cooling system (4-core rad, upgraded fan, etc.). I was planning to add an aftermarket trans cooler though.

An aftermarket trans' cooler is more so what l was alluding to, not the factory cooler incorporated in the radiator.

 

[OuchMyToe]

When you rebuild the trans, install the raybestos Z pac, wide band, upgrades drive shell, updated input sprag, hardened pump rings, and a decent shift kit.

Why does the Raybestos site indicate that z pack "rzp-001" is for 1988+, but resellers list it as 1982+?

Also, what constitutes a decent shift kit?

Finally, would it be more economical to piece out the rebuild or to just get a kit (e.g., "Monster")? After all, if I'm tearing into the trans, I'm ought to replace everything that could fail.

 

[HotRodPC]

An aftermarket trans' cooler is more so what l was alluding to, not the factory cooler incorporated in the radiator.

I get that, I'm just making sure it's known to USE BOTH. The radiator coolers offer benefits too and not only for cooling when you're in colder weather climates.

 

[HotRodPC]

Why does the Raybestos site indicate that z pack "rzp-001" is for 1988+, but resellers list it as 1982+?

Also, what constitutes a decent shift kit?

Finally, would it be more economical to piece out the rebuild or to just get a kit (e.g., "Monster")? After all, if I'm tearing into the trans, I'm ought to replace everything that could fail.

Don't do MONSTER anything. There are plenty of kits out there of good quality at good prices. I use transmissionpartsusa.com for most of my kits, then add other things I might want like bushings and thurst washer kits etc. Ebay has some good kits too, more of a one stop big master kit that aren't to bad, but I like buidling my own kits. Like that Alto commercial clutch pack, if I can find it, there's a clutch pack kit for your 3/4 clutch pack that lots of builders have good luck with, where some sweat by the Raysbestos Z pack. I personally prefer the Commercial Clutch pack just for the simple reason of what happens in the 3/4 clutch pack is cluthes cone with overheat. So how does it make sense to use even thinner clutches? OK, so theoretically what I say makes sense, but also keep in mind, the Z pack is designed to keep the temp and and the clutches tigher to avoid the heat, but if it does get hot.... KNow what I mean? So I just use the commercial clutch pack make up that many use and have good success with. Let me see if I can find the cheap clutch pack for you. If it's still available fpr that price.

 

[HotRodPC]

Damn, Trans parts have gone up too. Not as bad as lumber, but they've gone up.

Fits Chevy 700R4 4L60E Transmission High Energy Alto 3-4 Power Pack Kit | eBay

I like the Smart Shell too. I don't think you'd find it for any less than this. You can find all kinds of knock off for THE BEAST sunshell, or hardened shell from China and it NOT be THE BEAST. The Beast is good too, but the Smart Shell is actually better and worth it since it removes some strain off the rear planets also while being a stronger sunshell. The sunshell breaking is #2 failure of the 700r4 behind the #1 failure of 3/4 clutch pack burning up.
Sonnax Smart Sun Shell 77749-02K 4L60E 700R4 4L65E 4L70E SmartShell (99930)* | eBay

I'd so these upgrades and the Vette servro at bare minimum. With an aftermarket ADD ON cooler if you want to tow with it. Now you can go with THE BEAST sunshell if want to save about $25-30 over the Smart Shell, but for real, the money you're going to spend to do it right, another $30 is just insurance. I'd spend it.

 

[Dave M]

I get that, I'm just making sure it's known to USE BOTH. The radiator coolers offer benefits too and not only for cooling when you're in colder weather climates.

Absolutely, l tend to think of the radiator set up as an oil temperature stabiliser.