700r4 troubles

[TYCOBURBAN]

I was pulling my horse trailer today and my tranny temp gauge jumped to 220 all of the sudden. Then a little futher down the road it started surging in and out off overdrive between 35 and 60 MPH. Then when I get home I revved the engine and the speedo started to move but I was in park. Wh :confused: at gives i know allmost nothing about this tranny. any help would be wonderful thanks

[farmerpatrick]

I know this doesn't help with your tranny problems, but I noticed your at Eglin AFB. I was born and raised in Fort Walton. I'm in NC now, I just got out of the Marine Corps.. I'll be back in Okaloosa County in about 6 weeks. For good this time. Maybe we'll have a little diesel wheelin rendezvous.. I got a 4wd Blazer.. We could have some fun on the beach and in the swamps.
Are you stationed at Eglin? Gonna be there for awhile?

[BC Clark]

A couple of things I have learned after burning one up on the family vacation (climbing out of Kingman, Airizona at 100+ degrees) in my '90 gas sub.
1. The AAMCO guy in Flagstaff is a good guy and will work on (rebuild) your transmission on Sunday while you rent a car and go see the Grand Canyon anyway. I am not fond of the AAMCO chain but he put in a lot of hard parts besides the standard rebuild kit. And went halfies on the tow all the way from Williams to Flagstaff.
2. You should not pull anything in overdrive and that has nothing to do with the strength of the transmission. After I had the transmission rebuilt in my'90 V1500 sub, I added an aux. cooler and the Permacool external filter and temp gauge unit (Summit Racing has them). My sub with 3.42 gears lives on the ragged edge of unlocking the torque converter at freeway speeds in overdrive. What I have noticed is that in overdrive, the oil flow through the cooler is not sufficient to cool the transmission with the torque converter unlocked and therefore generating heat. Temps really climb even with the added cooler. Heat is what kills a 700R-4. In drive, the added RPM flows a lot more fluid through the cooler and the ratio allows the torque converter to lock reducing heat in the first place. The engine also pulls more air through the radiator and oil coolers. The 700R-4 will lock in 3rd and 4th. More than likely towing the horse trailer in OD kept you out of TC Lock and you cooked it. Overheating a 700R-4 will do more than just glaze clutch packs, the front pump and planetary take a real beating, and burnt fluid looses it's lubricity fast.
3. The speedometer on my '90 is electronic and gets it's signal from a sensor in the transfercase. Your two wheel drive has it's sensor in the tailshaft I believe. You said it started to move, was it just a flick or did it stay up while you reved the engine? What does the transmission do now? Will it go through all the gears? Irratic shifting can be slipping clutches or contaminated servos/valves. The filter in a automatic is little more than a suction screen, disintigrating clutches and burnt fluid will gum up the servos and valves. How many miles do you have on this unit? Has it been rebuilt before? Do you tow a lot?
Hard to say from just erratic shifting, but the reality is that if you have more than 100K on this transmission and you have to open it up you are probably looking at a rebuild anyway. The good news is that due to it's volume an popularity with the hot rod folks, there are a lot of places out there now that can rebuild it better than new.

[TYCOBURBAN]

yes Im stationed at hurlburt fld but I live on eglin. I will be here for a long time. not many places for me to go.

As for the tranny with out the trailer it works perfectly the only thing that i have noticed is sometimes it shifts really hard and somtimes just kind of slow and spongy. I bought the 1991 suburban used with 139000 miles and the odometer quit working at 169000. I have a Aux tranny cooler and the tranny fluid looked brand new this morning be for i left. But i did have it OD. as for the speedo it acted like a tach it would rise and stay steady with RPM's. I know when i have the trailer on the truck feels like it is taking forever to get going but i dont think it is excessivly slipping. Plus I'm running whatever the stock rear gears are do you think I should change them to say a 3.73 or 4.11 for better pulling. I only drive about 7 miles to work thru town so top end speed does not really matter to me.

[britannic]

The speedo is driven by a gear in the tailhousing on the 2wd and in t-case on a 4x4. If the speedo's moving, then the output shaft is turning the speedo drive gear. You'd better get underneath and have a look see.

Here's a really helpful forum, if the speedo thing is a red herring: 700R4 Forum (http://bbs.netgearhead.net/postlist.php?Cat=&Board=700r4)


Originally posted by TYCOBURBAN:
I was pulling my horse trailer today and my tranny temp gauge jumped to 220 all of the sudden. Then a little futher down the road it started surging in and out off overdrive between 35 and 60 MPH. Then when I get home I revved the engine and the speedo started to move but I was in park. Wh :confused: at gives i know allmost nothing about this tranny. any help would be wonderful thanks

[BC Clark]

If it's shifting okay now you might have just got it too hot. The 700R-4 will shift differently depending on load and throttle. The Throttle Valve, activated by the TV Cable on your throttle linkage changes both detent and part throttle shift points and shift feel by allowing hydraulic line pressure to build higher before it shifts. The later 4L60E dropped that in favor of full electronic controls (the "E" part of 4L60E). There is a quick adjustment that should be performed periodically with all 700R-4s. You push the adjustment tab through the rubber cover. Holding the tab down you move the plastic slider back until it touches the fitting. Release the tab and rotate the throttle all the way against the stop. The slider should ratchet out a bit. Check for full thottle movement and that's it.

The speedo is wierd, something's gotta be turning down there.