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95 Blazer 4L60E Reverse /Stuck in 4HI

evolve991

evolve991

Resident Problem Child
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Heerre we go again.....Bought a 95 Blazer that *had* a Reverse problem before it was fixed then parked for months. Owner was informed it was a dirty filter and fluid both of which were changed.
I've read,and been told,quite afew times that if Reverse was toast then it wouldn't have 1st either. Well it does apparently. So does anyone here have any insider knowledge on this?
 
There are two clutch packs that come on in reverse, the low reverse clutch and the reverse input clutch, if either fails you will have little to no reverse and full function of the four forward gears. If the splines on the reaction sun shell are stripped out then you will lose reverse, second and fourth gear. This is a very common failure on this vintage 4L60E usually caused by high line pressure induced by the ECM when the TCC regulator bore is worn out or a Mass Airflow Sensor is on the fritz.
 
Thanks Greg. It has all forward gears with no slippage. However it has 2 new problems: 1 it will not disengage from 4 HI now and 2 is blowing fluid from the top vent tube. It began as a drip off the cooling line but after I moved the line started coming out heavier.
 
Thanks Greg and Joe. Sorry,haven't been back here til now. I discovered the rubber hose attached to the TC vent tube has been cut halfway over the tranny. OK...common sense tells me that IF that hose is lower than the transfer case it will cause a siphon effect will it not? I drained most of the fluid from the TC and when started it's still leaking from somewhere up along the passenger side of trans.
This damn thing ran GREAT the day before ,although in 4HI,and not a drop....could a clogged filter cause the trans vent to blow fluid?
Just when I think I know all this transmissions little nasty tricks.............
 
evolve991 said:
Thanks Greg and Joe. Sorry,haven't been back here til now. I discovered the rubber hose attached to the TC vent tube has been cut halfway over the tranny. OK...common sense tells me that IF that hose is lower than the transfer case it will cause a siphon effect will it not? I drained most of the fluid from the TC and when started it's still leaking from somewhere up along the passenger side of trans.
This damn thing ran GREAT the day before ,although in 4HI,and not a drop....could a clogged filter cause the trans vent to blow fluid?
Just when I think I know all this transmissions little nasty tricks.............
Click to expand...

A filter can't cause fluid to run out a vent tube.This is assuming that the driver-operator hasn't poured several gallons of ATF into the dipstick tube trying to get the transmission to shift or move the vehicle.

What a plugged up filter WILL do is keep fluid from getting to the front pump and it will complain noisily.

It will whine, buzz and/or you will not get into gear - not that the command doesn't go to the circuit you are asking for - there's just insufficient or no fluid to push the pistons to make the clutches connect hard enough to get you to move.

That's a simplification of the process, but it will suffice for now.

Let's get this straight first ----> Is the 'tube' you see in the transmission or the transfer case?

Please refrain from using shorthand terms like TC or TR or whatever you are trying to talk about as it's confusing to someone (me) who is used to the full names of the unit in question. OK?

The true vent tubes are supposed to run as high as possible, usually to right behind the radiator support where they terminate in a kinda checkvalve that is supposed to keep water out of the line while allowing air pressure to vent. A vent tube is just that: a vent tube.

Serious off-road vehicles will sometimes have vent tubes as high as the snorkel intake for the engine. They are important to keep water, mud and pedestrians out of the gear sets.

Why even have a vent tube?

Images here: (these MIGHT be Jeep though, come to think of it - but the information is all good)

Because when you are running the vehicle and everything is up to normal operating temperature and you decide to cross a river or big puddle. Then the heated object gets quenched with cold water and it has to inhale quickly to equalize the internal vacuum that just formed.

Without an atmospheric vent, then it's the seals (wheel, output, input, shaft, etc) which will be forced to take water INTO them to relieve the vacuum in the unit in question.

Various hot-quenched components have to inhale from SOMEWHERE.

You SHOULD have the same-such vent tubes/lines on each differential, the transmission and the transfer case.

This is another time when the ability to post a picture is not afforded to someone who doesn't want to spend the money to become a premium member. Too bad.

Another thing - there have been a few transfer cases that I fixed that had pinholes in them and I found a video on that same repair if you want to see it:

This is not a commercial endorsement as I didn't use this product, but if a picture is worth a thousand words, then a video is worth a million.
 
I have used that same plate on three 263xhd transfer cases!
Two where preventative The last one I did was installed in a replacement transfer case for my sons truck, when we bought the truck it had two holes in it from pump rub!
 
Ok Joe thanks for the reply and sorry for the confusion.
It's a 1995 Blazer with 4.3 V6 and 4L60E, I haven't jotted down the numbers on the transfer case but assume it's an NP unit. It has trans fluid,not gear oil,in it. Drivers side drop. Push button 2HI,4HI,4LO

The "tube" is a rubber line ,or maybe 2 I can't see up over the transmission and haven't wedged my hand up there...yet..., I can see where the hose connects to the transfer case then runs up and over the transmission. I can see the other end ,which I assume and have read, connected alongside the trans dip stick tube ( I've never seen this done factory in my older chevys) with a plastic vent cap.

Also I found another rubber line which ends right around the cooling line fittings - I'm not sure it this is the transfer case vent hose and has been cut or if it is a seperate hose hooked to the transmission vent stub. It was wet but I haven't determined if it is what's spewing fluid yet. What started as a slow drip on the road became a fast drip,slight gush when I came home and pushed lightly the cooling lines looking for a pinhole. That's when I shut it down and started looking online for others who've dealt with this or something like it.

I read that it could be an overfilled transfer case due to the seal between case and transmission leaking. I don't have a 30mm and have to find my 1-1/16 socket or wrench so I used an adjustable but it doesn't fit into the tight space around the upper plug so I pulled the lower drain plug and got about a quart and a half of fluid out of the transfer case. I buttoned everything back up and started the truck,it still leaked although not as heavily,it was a gloomy day and my grandsons have helped me scatter all my flashlights everywhere except my truck and/or my toolbox so I still didn't locate the point of the leak. I guess I'm spoiled because my Suburban was easy to crawl around and gawk in tight spots compared to the Blazer which needs jacked and blocked up and the transmission is tucked tight against the body so I'll be using the mechanics braille method tomorrow.

I bought it off my Daughter in Law,I saw her driving it and heard no complaints except that Reverse was slipping sometimes. Her cousin told her that the filter could be clogged and cause no Reverse so she gave him the money to replace filter,gasket and fluid. Found out later ALL he did was empty the pan:angry1: He also had a piece of tape over the light on the 4HI button and the Blazer won't disengage back to 2HI. I'm assuming it's because it won't reverse enough to release,I'm not used to push button 4WD my 'burban was manual.
SO my plan,so far,is drop the pan and change the filter while finding where it's actually leaking from. IF it still has no Reverse I intend on ordering a TransGo or Sonnax boost valve kit,which I've read could be the problem.
It has all forward gears with no slip,no chatter,no surge. Drops into gear quick,no lag. Was not overfilled. Fluid is still red not burnt looking or smelling. I'll know more when I see the bottom of the pan.

If this explanation changes any of your answers or thoughts I'll be REALLY grateful :bow: for your advice. Or anyone else for that matter,I will never claim to know everything about....well....anything.
 
Yes - there are case vents for both the transfer case and the transmission case that usually rise to the firewall like mine did. I don't remember them being tee'd into each other - but could be.

Actually if you've got a 4wd, you'll likely have four such vents for the two differentials and the transfer case and the transmission.

Servicing the transmission by dropping the pan and changing the filter and the gasket - if done on regular intervals - is more than sufficient and qualifies as a good enough service to the transmission. It also affords you the opportunity to see any debris and junk in the pan - if indeed, there is anything in it.

Yes - the transfer case and the transmission use the same fluid - ATF - and I've just taken the inter seal out the the two so the fluid can move back and forth. Doing that - the transfer case will be significantly overfilled - which is OK with me as I have straight cut gears in mine. The fluid doesn't move around fast enough to cause any starvation.

For the record - there is very little fluid pressure in the cooler lines - just enough to move the fluid through the heat exchanger* (fluid cooler) - and I have seen some tests that indicate about 3-5 lbs/pressure is normal and as you can see, it's very small and quite insignificant.

* this is NOT a "fluid cooler" although some uninformed persons will call it that - it will raise the transmission fluid level to 195F - and that's because the thermostat in the cooling system keeps the engine at that temperature for good reason.

ATF works best at that temperature too - so the idea is to keep the ATF in that range as best as can be done with short hops and long hauls at either end of the driving spectrum.

It's staying at a regular and designed-value temperature that makes a transmission live a good long time. Cold and overheat kills them!​

You should not have any restrictions in the steel lines themselves as they are decently large enough to not plug up.

However - the heat exchanger is capable of getting stuffed up from entrained clutch debris and steel/aluminum shards from just about anywhere and it could create enough backpressure to make a rise in pressure in the discharge side of the fluid lines. Rare - but possible. Still, it's unlikely.

MAYBE this transmission was a rebuild exchange and the cooler was never properly changed or flushed (not always a great idea!) and they didn't want to pay for that repair/service and now their failure to do what's right is catching you by your narglies.

So - the steel lines aren't a likely culprit - but the rubber flex hoses are a larger possibility.

I'm gonna guess here and say that when you moved the cooler line it may have been deteriorated enough to have caused a kink in the line and that could be your problem.

As for the slipping in reverse - it's never good and it can only happen for a few seconds while the clutches burn and they are toast. Boosting pressure may or may not work, and any repair valve to help with a slipping reverse is just a band-aid at best: Your unit needs an internal repair and there are no mechanic-in-a-can that will likely work much - or at all.

OK - here's another part to check - ARE THESE REALLY cooler flex hoses or someone's mistake when they put vacuum hose or garden hose on the lines for a cheap and incorrect repair?

Hey! - late epiphany! - check to see if someone put rubber hose in the fluid lines near the transmission itself.

There could be a ruptured hose of questionable quality, or just plain wrong hoses there by ignorance. Or cheapness.​

I've seen do-it-yerselfers cut the steel lines because they don't have the right tools (flare nut crowfeet) to access the fittings and just put a piece of rubber hose over the rough ends of where they cut the lines with a pair of sidecutters.

Yup, seen it. Fixed it a few times!
 
The cooler lines are steel from trans to radiator,yeah I've had the old rubber line patch catch me by the short n curlys a few times :frown1:
You actually did away with the trans to case seal huh? Pretty cool ! Makes sense to me.
Heat exchange- I learned the hard way when I had my 700R lines hooked to only the add-on cooler,it was fall when I did that and when winter set in I had hard,late shifts constantly because it wasn't warming up with the motor.
I don't trust,or use,many solutions in a can. I'm praying it isn't the sun shell going bad,I just junked my Suburban because the rebuilt 700r4 blew and left me stranded IN Baltimore about 50 miles and a major river between it and home. No AAA,no buddies with a monster vehicle and towbar and I was a day short being done hanging the job so flat broke wasn't paying any rollback costs.
I can get by with no reverse for a while with some creative parking,etc but I need to know where it's leaking and why. Tomorrows my first day off since the leak started so I'll be under there trying to figure it out
 
Just got the chance to crawl under the Blazer. I'm almost positive it's a leak in the cooling line now,it started dripping heavy again when I loosened the fitting on the radiator. I wasn't running or even started today.
QUESTION: Do I have to drop the Y pipe to drop the trans pan? Looks like there *may* be just enough wiggle room but I'd rather know before spending time looking for the exactl angle
 
You don't need to drop the pipe but you stand a good chance of breaking a shift solenoid if you try and worm the pan out so be careful.
 
There is no external cooler,I blew air thru the radiator trans fittings,no debris. Fluid is red/clear with no metal or even sparkly shavings. Upper line was wet at fitting and really corroded. I'd swear someone put something highly corrosive on the lines as well as the brake lines which I replaced already. Everywhere it leaked looked horrible,the rest of the lines looked fine. And the corrosion wasn't where they'd easily be doused with water or mud,it was all up high and hard to get to. Previous owner has a scheming druggy cousin who liked to exaggerate problems and overcharge for fixing anything.

Update on the paranoia theory: I found a nice little sawzall cut on the exhaust pipe while working on the tranny lines. A certain meth freak/garbagehead has a future surprise visit in his tweaking,nodding,felony artist world........
 
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I've got the 3 button 4WD setup. Blazer has been "stuck"(?) in 4HI since I got it. I pulled the battery shelf and checked out the vacuum actuator,the vac line was unhooked. I hooked it back up but no dice,won't switch back to 2HI but the engine ran a little choppier with the line connected. The actuator didn't slide either. Is it possible to manually unlock the front differential at the actuator without vacuum functioning?
 
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