I have a problem that has completly stumped me. I'm trying to figure what the cause could be. I have a 1994 Full size blazer with a 4l60e tranny that would not go into Third\Overdrive. It acts as if you have shifted to neutral.
I have ordered and Installed a Master Rebuild Kit, new torque Convertor, new piston\accumulators, a new reman Valve body with all electronics.
Still does same problem. Wierd part, IF you put the rear axle up on jack stands I can run the speed up to 65 and it seems like it is shifting fine. It tachs at around 2000 rpms. I can rev it up and down and it seems normal.
Drop it back down and I can't go over 45 mph and taching at 5000 rpm. Shifts into nuetral again. If I punch it it will downshift into second again but drops back into nuetral when it gets up to speed.
I have had the thing off and on the stands twice to verify this behaviour.
I'm trying to fix this for my son but have spent countless hours trying to pinpoint problem.
Any pointers or direction to check in I would appreciate. What would cause the shifting to be different depending on if the wheels are touching the ground or not? I know when they are on the ground there is more torque on the tranny but what would control the tranny so much that it would completly throw it off so it would not shift, some sensor bad, computer??
I was following a rebuild DVD during the build and I remember that it showed how to find and check it. I cleaned it out and verified movement. Although something I forgot to mention was that right after the rebuild it ran for about 30 miles and worked. Then it went right back to the same problem and has never came out. I then pulled and replaced valve body in a shotgun diagnose method. This did not fix it. I supposed the check ball could have been loose and stuck again. Can I check this without pulling the whole tranny out? Can I access this by repulling the valve body?
Yes it does have reverse. First and second gear work solid.
yes by pulling valve body and looking up(dont get fluid in eye it hurts) take a pick and can check ball for movement. also, was 3/4 clutches fried in trans? if they were and when dropping pan alot of black stuff probally burnt up again.:sad: thats the big drum with 3 clutch packs in it. the top 1s are 3/4. when clutches are up looking at you.to fix it now right.replace drum maybe a cross leak. also replace stator in the pump since that is where the drum gets applied from and the inner stator can turn and block off holes to loose pressure to clutches.i always replace in a rebuild tranny.sonnax or other companys make it. also there a valve you put in case to help those weak 3/4clutches made by sonnax also.also if 3/4 piston is cracked it will burn in miles. valve body gaskets in wrong position or wrong year also will do it.in kit a white stripe is for 2001 and up use others. the one that has a vb goes to the valve body side and other may have a c for the case side under the plate. also what comes into mind is checkballs the front 1 in vb likes to get stuck in the plate.either change plate or got plate savers and put 1 in the plate file down with file to be flat.
When I pulled the pan there was a lot of black particles and bits of metal, like little wire shavings. After the problem reoccured I found the 1-2 accumulator valve was sticking in the valve body, book states ID number 371. So I replaced with a new valve body but like you say the damage is already done. My dilemma is what to do next. Was the sticking valve the root cause and replacing clutches will fix. I need to pull it apart and reinspect all the items you mentioned. Not being experienced I may miss the problem again and wind up with the same issue.
OR buy a rebuilt tranny from Autozone for $1300. I already have about $600 in parts in the old one.
Just for theory of operation purpose, Why do the clutches burn up so quickly when something like this is wrong, is it lack of pressure and why do they fry so fast??
thats the biggest problem with that trans the 3/4 frictions.get sonnax valve part number 77701-076. and also 77898e-k a pressure valve and 77918s-k the stator if inside stator turns it blocks hole to 3/4 clutches. the first valve helps regulate 3/2 control oil and pr valva raises pressure some also back of solenoid by wires take a torx bit and turn 1/8 turn get alot better shifts out of it also. when you back in there theres also alto or from sonnax they call it a beast pack for 3/4 clutches. there thinner and then you get more in there. those 5 spring thingys on out side of clutches throw them away dont use them. as for the clearance in that pack measure snap ring that holds clutches in and you want that much between top plate and snapring.any transmission supplier has these parts. for the stator take 3 torx 27 out and hit from other end to get out installing it use a bearing race installer and hit it to flush dont use press lol. (you will be buying a pump )
My wife has given me the OK to get a rebuilt tranny if needed, BUT I want to give it one more try to fix the problem. I will use all your advice this time while it's apart. If after all that it still fails I will give in and get the new tranny. I don't mind doing the actual rebuild but pulling the tranny and reinstalling in a 4WD on my garage floor is a pain to say the least.
Thanks for all your help and advice. I will PM you after all done and let you know how it turns out. With my schedule it will take me about a month to complete everything.
when you got it apart pm me ill help you before you put it back together to make sure you got all things covered. ive been doing transmissions for 22 years :beers: if i dont know now i should throw in towel lol:thumbsup:
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