Ok, my S10 Blazer has been sitting for 2 yrs or so. The transmission worked fine when parked. About a year ago I pulled the pump, overdrive clutches and the input shaft/planetary thingy that attaches to the input shaft. I swapped input shafts with one out of my trucks transmission (Blazer had a billet shaft) I put it back together and it has been sitting until now. I used the converter out of the Blazer in my truck for a while and it worked fine but I took it back out cause the stall wasn't right for the truck.

So now I have the new motor in the Blazer and the trans is acting like a fool. It will not engage any gears forward or reverse until I rev the **** out of the motor. I can put it in park or neutral and rev it to 4 or 5k a couple times then it will engage. It may or may not "slip" (by slip I mean move forward or backward but require more RPM than normal to do so) at that point. If it does "slip" I can kick it in neutral and rev it a couple more times then it will engage like there is nothing wrong. I drove it on a 10 mile trip and it shifted fine. Had all gears plus had converter lockup like it should. Shifted great under WOT. Get home, turn it off, start it right back up and NO ENGAGEMENT. Rev the motor and then it engages...WTF??

Today I dropped the pan to take a look-see. Nothing appears out of the ordinary...checked the valve body bolts just to be sure....everything looks good. Put a new filter and filter seal in, filled it back up and guess what-no engagement til I rev it up. Gonna put a gauge on it tomorrow if the guy I loaned it to brings it back. Could I have damaged the teflon rings on the input shaft when I swapped it? Would that cause this kind of prob? I sure dont want to have to pull the trans!! Help, somebody please help!!!!

 

Are there any diagnostic codes?

 

No, there are no codes present.

 

Ok I just got back from driving it with a pressure gauge hooked up. Upon initial startup it shows 75-80psi. Drop it in reverse and pressure goes to about 125...no engagement. Put it in drive pressure is 80ish with no engagement. Put it in park, rev the motor to 4000-5000rpm and pressure touches 150 peak. After a couple revs put it in reverse and it engages fine. Back out the driveway with 125psi in reverse, pull away in drive, shifts 1-2-3-4 just fine. Put it on the floor from a 20mph roll and it downshifts to 2nd, pressure goes to 175-180 shifts nice and firm to 2nd no problem. Pull in driveway let it idle-shows 75-80 psi. Turn it off, wait 30 seconds start it back up-75-80psi and NO FRICKIN ENGAGEMENT!! GRRRRR what is wrong with this thing??

 

Another update...I got the electric fans wired up so I was letting it idle watching coolant temps. At about the 4 minute mark I decided to put it in gear just to see and it engaged just fine without having to rev the engine.

I then did an unscientific test-I checked the fluid level on the stick after it sat awhile with the engine off. I noted where the fluid was then started the engine. The time it took to drop down to the full mark is in correlation to how long it takes until the trans will engage without revving it up (a couple minutes). Then I went to my truck which has a 4l80e also and did the same test. In the time it took to walk from the driver door to the dipstick the fluid level dropped down to the full mark, not taking a couple minutes like the Blazer does.

Its like the pump is losing prime or the converter is draining and taking forever to fill back up. Why is the line pressure the same whether it engages or not?? I would think if the pump wasnt working or not pumping as much as it shoulc the pressure should be less??

 

Well, took it out and beat on it this afternoon. I have been planning on taking it to Super Chevy in STL this coming weekend but now I cant go anyways so I figured I would be hard on it and see what happened. I made several 0-70 or 80 mph passes. Several full throttle downshifts from various speeds (2-1 downshifts, 3-2 and 4-2) The only weird thing it did was a couple times from a dead stop the converter flashed to 4500 or so instead of its normal 3000ish. It did puke a very small amount of fluid from the vent once (just enough to make a little smoke) Once I got close to home I beat on it some more and it shifts nice and hard. Can this be some kind of weird converter problem?

 

Sure sounds like a fluid pickup issue. Check the filter and seal.

 

I replaced the filter and seal earlier this week. Im thinking I might as well pull the dang thing

 

How about pulling a cooler line and check how flow is compared to engagement?

Chris

 

Hello sir. Sounds like a pump or a converter issue or yes a torn sealing ring when you re-installed the pump.

If could also be when you installed the hardened input shaft you have to make sure you lined it up to the feed holes in the forward drum.

The best thing to do is, is pull the transmission out. If you have any other questions please give me a call and lets see if we can fix this issue for you.

 

Have you ever even assembled a 4L80E?

 

+1 I have built many 80's and never had to line up the input shaft. I'm thinking Lou is making a reference to a 60.

It sounds like the pump pressure is good. I know issues like this can beat you up trying to figure out what is wrong. Do you have the same delay in all ranges? If you put the shifter in D3, D2 or D1 does the same thing happen?

 

I've seen a 4L80E with a misinstalled converter that the pump cover was worn badly, yet it still made decent pressure on a gauge, it would have delayed engagement or need to be revved to work.

 

I get it Jake no argument here. You and I would have inspected all components before reinstalling them and as we both know 80's can be a little hard on pumps. I'm curious if this happens in all ranges and if possibly there is an issue with the OD roller. I have seen some weird complaints with the late style one way clutch. I'm sure we both will agree that the large OD roller is the one of choice. It was just another option to check.

 

Chris-I will pull a line tomorrow and see how much fluid comes out. What will it tell me if a normal amount comes out or if little comes out?

Why is the line pressure the same whether it engages or not? It has to be bleeding off somewhere past the pressure port in the side of the case, right? I have been reading what limited info I can find on the hydraulic circuits trying to understand where the fluid goes once it leaves the pump. In the grand schemeof things how far down the line is the pressure port from the pump?

Vince-yes it does it in all forward ranges as well as reverse. And fyi, I think this unit has the later OD roller....but if it was shelled it wouldn't work sometimes would it? The dang trans works great once it engages.

I just keep thinking about the fact it worked fine til I took R and R'ed the input shaft. It actually probably only has 10 1/8th mile passes and a couple hundred miles on it since it was rebuilt (like back in 2007 or so)

 

Not sure it will tell you much. But normal flow is about 1-2 GPM depending on RPM. But at idle I have sen it as low as .5. So not sure it will tell you much.

How was the converter spacing?

Chris

 

Well, its easy enough to check...I will do it tomorrow. The converter spacing is around .160 without shims. I have .060 flatwashers between the flexplate and converter.

 

Not arguing Vince, just stating some things I've seen on 4L80Es.

I've also seen them limit pressure to 125 psi in any range due to cracked case on the line pressure circuit, where it comes around the "corner" in the case and there is a large surface area for line pressure to blow out the case.

I don't think this is the issue here.

I would pull the pump and look at the pressure regulator, where it goes to the converter feed circuit (round hole in the rear pump half, at approx center of PR valve) and be sure nothing is stopping converter feed.

Obviously look at the OD roller and input shaft seals while there.

 

Pull the shims and see what happens...

Chris

 

Ya know, that got me to thinking...that is something I did different this time around. I didn't use any shims the last time this combo was together. Hmmmm