Shift from park to reverse kills the engine.

I am new to this page so thanks for the add. I recently(yesterday) swapped in a rebuilt A 904 (that had sat on a shelf for 7 years) in my 86 D150. The trans that came out was an electric lock up unit and I am now using a mechanical lock up unit. When I got it all put together, I went through the gears and reverse seems to kill the engine almost immediately. I can keep it running but I have to slam hard on the gas to get reverse to actually work.

Right now, I know that the shift linkage needs to be adjusted. I couldn't get the adjuster un stuck (rusted on shaft) so I was just trying to get it going. However, I am thinking that the torque converter is locking up in reverse causing the engine to stall? It drives fine in all forward gears. Could this be a band adjustment that is wrong as well? I know nothing about the trans other than it is older than the unit that originally came out.

Has anyone else had this problem? Any information is greatly appreciated. This is a daily driver so the sooner it is fixed the better.

HARV

The mechanical LU type trans has several valves that should only permit converter LU in 3rd above a certain speed. It sounds like you have LU going to reverse- that would point to some kind of problem in the valve body. Either a valve is stuck or was installed backwards, missing a spring, etc. The 3 you need to look closely at are what's called the lockup valve, the failsafe valve, & the switch valve.

If you rev it up too much in order to go into reverse w/out stalling, sooner or later you'll break something- usually the Low/reverse band or strut.

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63 Valiant Wagon
225 - 4 bbl

Why did you change transmissions? Was the old one not working anymore?

An engine dying when it is put in gear is usually indicative of some other problem with the engine such as a vacum leak or incorrect timing. Basically the engine is running so poorly that any load put on it at idle kills the engine.

Lockup in the mechanically controlled lockup trnasmissions is controlled by a sping and a valve in the top of the valve body. I suppose it is possible that the valve has become jammed in the compressed position or the spring has failed allowing the valve to operate at idle, but the valve should not be engaging in reverse.

Drop the an, pull the valve body, and inspect the lockup valve.

I delved into playing with the lockup control on a 904 and discussed it in this thread. Click on the red text. That link will show you the spring and valve I am talking about and where it is on the transmisison valve body.

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Casually looking for a Clifford hyperpak intake for cheap.

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So I got the trans to shift great in drive throughout the forward gears but reverse still kills the engine. I cleaned the cooler lines and that seemed to help for a little bit but then it did the same thing again. I am going to try and clean the cooling system one more time. I think there is something sticking in reverse. It feels like the torque converter is locked up... only in revers though. It drives like a manual whenever you take off from too high a gear, like a clutch dump. Any suggestions out there?

I have ruled out a faulty pump since all the forward gears are working perfectly. Shifts and lock up are with in specs.

Would a revers band have anything to do with this?

HARV

I am by no means a transmission mechanic... Is there anything that I need to be concerned with if and when I pull the valve body? I was kind of thinking the same thing after driving the truck in forward gears perfectly.

HARV

Oh and I changed transmissions because I lost second gear.

HARV

'Sat for seven years' isn't usually a good thing.
Lots of valves can get stuck from sitting that long.

When you pull the VB, keep track of the check balls and make sure they are where they belong.
Look carefully for cracks in the VB casting.
Pay attention to torque specs when reassembling so you don't get cross-leaks.

You might consider checking the governor for sticking as well, although it's inside the tailshaft.
Front pump wear could also account for this problem.

Do you know why this tranny was put on the shelf in the first place?
Did it ever work properly after the 'rebuild'?

You might end up pulling it back out and going through it in detail, or fixing the old one.

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O==\=/==O

"A mechanic is Somebody."
- Jim Preston

the guy I got it from ( who owns a transmission shop) said he rebuilt it for another guy seven years ago and he never paid for it or came back to get it. So, it just sat on the shelf greased and ready to go for 7 years or so. I mean this thing shifts awesome in forward gears, better than any other 904 that I have ever had. I talked to him today and told me to take the rear cooler line off and route it into a jug... start the truck and put in neutral... said it should be about a quart of fluid in 20 - 30 seconds. I am guessing to make sure that the cooler lines are free (even though I blew them out with compressed air) or to make sure the pump is working ok.

In the mean time he said that he was going to do some research for me and call me back. I am pretty sure that he and I both want the same outcome...A working 904 in my truck.

HARV

I have found this diagram extremely useful in diagnosing what part of a 904 transmission has failed:



If the trnasmission works well in all forward gears, I susoect a problem in the valve body. I recommend removing the valve body, thoroughly clenaing it, and then reinstall it.

_________________
Casually looking for a Clifford hyperpak intake for cheap.

I am convinced it has to do with the torque converter locking up in reverse. So, I am thinking a valve body removal, cleaning and install will be in order. I have never done one before so i am a little nervous. But as long as I am careful I should be ok.

I suspect a sticking valve that controls the torque converter clutch in reverse at this point.

HARV

Ok so there is a new development... Transmission kills the engine in reverse whenever it is hot. So when the motor is cold, it holds in reverse... Not sure what this means

HARV

anyone have any other ideas?

Did you remove and clean the valve body? Did you verify proper band adjustment?

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Casually looking for a Clifford hyperpak intake for cheap.

next two things on the list

So, I pulled the valve body, cleaned it, made sure everything was moving, freely, installed all the spools, springs and check balls in their proper positions with assembly lube. Put it all back together with new trans fluid and filter and it still kills the engine in reverse WHEN HOT.

The thing shifts great when it is cold but as soon as it reaches operating temperature it dies every time in reverse.

I also noticed that the fluid is aerated. Could this point to a pump problem? Anyone?

I think that I will be taking this unit back and getting my money from the rebuilder.

I installed a slant 6 727 that I had laying around and am already more pleased with its performance... Not that is without it's quirks... I think that the torque converter is weak due to the shudder but it seems to shift ok.

Thanks for all the help