Need help with Chev Z71 PU tranny problem

[Bob A.]

My son owns a Chev Z71 P.U. with a 5.7L. engine and 3-speed auto transmission with over-drive. He bought it used with 100+K miles. Very clean and very smooth running.

He was towing a tent trailer this past weekend and experienced several "hiccups" in overdrive. The truck runs great in D, but "hicupped" several times in overdrive on a 370 mile round-trip in hot weather (100 degrees F), going over a mountain pass.

Any additives or ATFs that might help? For example, Amsoil has come out with a couple of new transmission fluids.

Or is the OD going out?

Suggestions?

Bob A.

 

[04SpecV]

What year is it? I think you mean the 4l60E. Its not recommened to tow in OD with that transmission.

 

[Bob A.]

It's a '94, 04SpecV. I don't know what the 4l60E is. I assume it's the transmission.

I'm just passing on the info. from my son . . . looking for some input: '94 Chev pickup with 5.7L engine and 3 speed auto transmission with an overdrive that hiccups.

Your info. wasn't lost on me. I guess that your suggestion is probably listed in his owner's manual, eh?

Bob A.

 

[aualtima3.5]

I would agree with 04specV: leave it in D, (3) whatever, when going on inclines. The constant shifting the transmission does is further damaging it by increasing fluid temps due the multiple shifts.

I would do a fluid exchange and add a transmission cooler. At the least the cooler. You can pick one up for around 30 bucks.

And the 4L60E is no transmission to give crap. They die easy.

 

[Rhymingmechanic]

I'll third what the others have said--have your son change fluid and filter, install a good sized cooler after the one in the radiator, and tow in Third, not Overdrive. He could probably pass on synthetic fluid until it's clear the trans is OK. Installing a drain plug while the pan is off will make future fluid changes easier. If the trans is mechanically sound, shift improver kits are said to improve lubrication and clutch application as well. Does he know the transmission's service history?

Hoping for the best, my uneducated guess from the information you gave is that heat caused his hiccups. Lots of what I've read about the GM 4L60E and 700R4 overdrive automatics, especially the early ones, suggests they generate a lot of heat and that an auxilliary cooler is mandatory for towing and performance applications.

 

[Bob A.]

Great info., guys. Thanks. His rig does have an auxiliary transmission cooler, but my guess is the fluid probably hasn't been changed and is in need. He doesn't know what the service history is.

I like the idea of installing a drain plug.

Any transmission fluids you recommend? Dino, syns., semi-syns. (if there is such a thing)? Stick with the Chev product? Are there better aftermarket fluids? Any cooling type additives?

 

[TxGreaseMonkey]

Drop and clean the pan, replace the filter, install a B&M drain plug in the pan, install an auxiliary B&M transmission cooler, drain the converter, and fill with Amsoil or Mobil 1 synthetic ATF. I have seen many truck transmissions boil over in Texas who did not use synthetic ATF--it makes a big difference. Nothing like seeing ATF boil up through the fill tube or transmission vent all over the ground. In hot West Texas, it's not cheap to have your truck towed several hundred miles home.

 

[TxGreaseMonkey]

Bob A., I would also drain the differential and fill with Mobil 1 or Amsoil synthetic gear oil. Also, give consideration to installing a transmission temperature gauge.

 

[Bob A.]

Thanks again, everyone. He'll do the following:

1. Not tow up mountain grades in O.D. . . .
especially during triple digit weather in
the hottest part of summer.

2. Drop and clean the pan -- and replace the
filter.
3. Install a B&M drain plug (or comparable
model available in the P.N.W.).
4. Check to see what transmission cooler he has and
if it is of sufficient capacity. Adjust, or
not, as needed.
5. Install a transmission temperature guage.
6. Fill with Amsoil ATF.
7. Drain the differential and fill with either
Amsoil or Schaeffer's fluid.

Much obliged. Your responses provided really good info. and suggestions. We are indebted.

Bob A.

 

[TxGreaseMonkey]

Bob A., sounds great. Don't forget to drain the torque converter. Over half of the fluid resides there.

 

[Bob A.]

Yeah. I forgot to list it in the "to do" message, but didn't forget that it needs to be done.

Thanks again, all!

Bob A.

 

[Mike_dup1]

On a high mileage vehicle I would have a good trans shop do this for you. They can evaluate the fluid and what they find (in anything) from dropping the pan. If all looks good, go ahead with Amsoil fluid. But I would not blindly install pricey synthetic unless I was 100% certain I had not pending trans problems. Like you said, you don't know the service history and lots of things can happen to a vehicle in 100,000 miles.

I had a good friend with a 1994 truck and his trans up and failed out of the blue one day at around 37,000 miles. He was bummed out, truck was still under the time warranty (got it new) but over the mileage. Chevy dealer told him that some were prone to failure and Chevy would cover a new trans at over $3g. That was way back in 1995 or 96, fat chance of getting anything today. They said as long as he was still under time warranty, the zone manager would approve on a case by case basis.

 

[Bob A.]

Thanks, Mike. It's always an interesting game with the dealers and the manufacturers. I'll spare you the details about a verbal exchange my daughter-in-law had at a supermarket with the used car salesman who sold my son and her the truck.

Actually, the truck is a really good one and was a good deal, despite the transmission "hiccups". But the dealership owner's attitude and response was really offensive when he was approached about their responsibilities in the deal.

Why does it always require that the consumer become an ***hole in order to get some semblence of justice? 'Tis a true trial of patience and grace . . .

 

[Mike_dup1]

Never trust a car dealer or salesman, just too many that let money be thier god.

I know someone that bought a demo truck from a Chevy dealer. Nice truck, short box Silverado 4x4 with all options. Paid a great price, truck had something like 1800 miles. They told him it was the owners truck to drive. Nothing ever went wrong or anything but many months later he was doing something inside the car and had the hood open. He is checking the oil or something and can see light shining thru hole in firewall. This get him wondering why a hole is there, looks closer and you can see its been drilled. Hmmm? Still has him bugged so he stops at a friends reapir shop to get his opinion. He is shocked what the guy tell hims, that truck had a snow plow on it. Sure enough, he points out other mounting holes under hood etc where the control where. So he is po'd, goes to dealer and aks's did this truck have a plow? Yes it did, but we told you that, yadda yadda yadda. He swears to this day, they never said one word. Never had a problem with the truck in 10 yrs or so he had it but its always bugged him they never mentioned that fact. (not same guy with trans problem)

 

[vicmackey]

Oh god here we go with the "let me one up you with my salesman story" tirades.

 

[Scooby]

quote:

---

Originally posted by Bob A.:
My son owns a Chev Z71 P.U. with a 5.7L. engine and 3-speed auto transmission with over-drive. He bought it used with 100+K miles. Very clean and very smooth running.

He was towing a tent trailer this past weekend and experienced several "hiccups" in overdrive. The truck runs great in D, but "hicupped" several times in overdrive on a 370 mile round-trip in hot weather (100 degrees F), going over a mountain pass.

Any additives or ATFs that might help? For example, Amsoil has come out with a couple of new transmission fluids.

Or is the OD going out?

Suggestions?

Bob A.

---

BOB A: I'm not a real smart man, so go easy on me. Based on your vague description "hiccup", I'm not totally convinced this is a problem with the transmission. More information is really needed.

But like has been said, he should not tow in OD unless he is on flat grade and transmission isn't hunting.

 

[04SpecV]

I bet it has the original transmission fluid in it

Probably the diffs, transfer case also have original fluid. The only way it wont is if some car nut had it, which isn't that likely. Might wanna check the Antifreeze, brake fluid also. Check brake lines, etc.
Unless this truck has a modified engine, I cant see it towing up hill in OD anyways. My truck(93) is at like 1500RPMS at 55 in OD. What gears does it have? Probably 3.73s.