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What did i break (in the transmission)?

D

dudeiwin86

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Apr 2, 2010
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Location
Houston, TX
1990 K5, 350 TBI, 700R4

So i was leaving work yesterday, start the car, pop it in reverse, roll out of my parking spot.
i put my hand on the column shift and start to pull it out of reverse gear as im rolling backwards. start to move the column to Nuetral and it slips all the way into drive.

im a strong advocate of coming to a complete stop before shifting into drive (from reverse) and i know better than to screw around going into nuetral while im rolling.

did it anyway.

so i hit drive while still moving backwards and THUD! and it jerks forward.

well it drives fine so i *think im in the clear.
not.

after coming to a stop and leaving with a bit of UMPH... it grinds.
grinds awful loud.
if i get to the top of first gear with close to wide open throttle you hear a BANG... BANG... on the floor board as it rattles the coins in my center console.

so i drive softly... and its fine.
but in ALL GEARS (1,2 and D) it will grind if i leave semi-hard from a light.

it sounds very similar to if you were driving.... and threw the car into park.
that kind of grind....(never done this, but i witnessed a friend do it a few times making very abrupt stops offroad.. lol)

my initial thought is that its the lockup clutches in the torque converter. since it seems to happen no matter what gear im in, and only off idle... as if the lockup clutch is slipping while until it gets enough pressure to be fully locked?

i really dont know... but im hoping it wont be a full rebuild.. i was fixing to buy 3/4 tons and a crossover steer setup.

any ideas would be great.
thank you!
 
back end of the transmission is getting ready to shell out better find yourself a good transmission.
 
my '94s 4l60e died several months back, did some grinding noises, broke while pulling a trailer, turned out to be the planetary gearset, broke one of the gears, and the surrounding shell it rides in. nasty noises, and loud.

i like the idea too about hearing an odd noise like that, and mashing the throttle to the floor to try to regain a normal working unit.... how'd that work out for ya... :whistle:
 
hehe, i know i know.
i was trying to "diagnose" the problem.
my verbage above makes it sound a little more retarded than how i really went about it.
doesnt really make me any less of an idiot considering how i screwed it up in the first place. i will admit to that!

it has only happened intermittently, so i took it for a short drive trying to make it do it so i could figure out if it was in a certain gear or not. hence the mashing the throttle in each gear.

i guess 206k miles on this 700R4 finally gave up the ghost. then again, i dont know if it has been rebuilt before. i would have to assume it has.

like i said, it does not appear to be gear related. it will do it in all gears, but only from a dead stop under decent load.
if you baby it, no sound.
once there is momentum in the drivetrain, there isnt enough load on the trans to cause it to grind.

at least now i have a good excuse to build it bigger and badder.
thinking about going to a manual.
another stupid question. does the ECM/OBDII stuff care what transmission is in there?
could i run something like a SM465 or maybe a 4l80e?
but this would probably necessitate a different t-case wouldnt it?
 
you put it in reverse yet? see what it does then?

when mine died, it would pull forward (noisy), but if you put it in reverse, it would just freewheel and grind like crazy again.

the forward movement had a fast ratcheting type sound, like gears skipping over each other :D
 
reverse works fine. infact, i havent heard any grinding in reverse, but ive have been just letting it roll with no gas in reverse.

the ratcheting sound is pretty accurate.

ive been driving it and just trying to baby from each stop.
im almost done rebuilding my other toy, so i just need this to hold on for another week or so. then ill have room in the garage to work on it (if i can even get this huge thing in the garage...)

i started thinking... and im wondering if maybe i took a tooth out of the rear end? or scattered the "gov bomb"? the rear end was already howling since i bought the thing, and maybe its catching a little bit and is causing the grinding back up towards the transmission/tcase?

the transmission does not slip or have any issues once its got some momentum in it. its just from a stop and its not like any noise ive ever heard a transmission make.

ill be pulling the rear cover off the diff this weekend.

even if it is the transmission, at least it will give me an excuse to build the 700r4 to take some abuse rather than not knowing what was under there and if/when it had been rebuilt.
then i can put in a floor shifter at the same time and have a little more accurate control! ive always hated the column shifter ever since my old suburban.

breaking parts is the best excuse to upgrade :)
 
I wonder if the sungear shell isnt fubar, or like others said the planetary could be messed up too.
 
Don't overlook u-joints. If not u-joints then I would suspect a cracked sungear shell and eventually you will start losing gears.
 
Here are a few troubleshooting ideas:
-The torque converter and pump spin all the time. If your problem is there, you will hear the sound even when the vehicle isn't moving.
-If you tape a plastic cup onto the rear output of the T-case, you can pull the rear driveline and use front-wheel drive to eliminate the driveline and rear end.
-I would take the rear diff cover off to check before I would take the transmission out. That's like a 1/2 days work.

You may have cracked the sun shell or broken a sprag clutch.
 
thanks for the tips, blue85. will do. hopefully i can make some time tomorrow to get the cover off after work.
 
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