700r4 Transmission Meltdown
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
700r4 Transmission Meltdown
I brought this topic to light last fall, but I want to revisit it since I will hopefully be getting something done with the car in the next week.
I have a very interesting problem that needs to be solved. I have in my possession a 1986 IROC-Z with a stock 305. Here is where the mystery comes in. I drove my roommate to his class. I stopped at a stop sign then took off. The RPMs got no higher then 2.5k. Then I heard a bang and I lost power to the rear wheels. I didn't beat on her that day at all. I got it towed to the auto shop and they said the transmission is the issue but they didn't tear into it to see what's wrong.
Issue:
-Accelerated from a stop sign heard a bang and then no power to the rear tires.
-Wasn't beating on it.
-All gears are gone.
-No slipping or anything before the total loss.
-A sprag on it did break last spring and the warranty covered that, but now the warranty is over (as of September last Fall two days before it had a meltdown).
Before someone mentioned it could be the other sprag going this time, but my question is why did forward and reverse go out at the SAME time if it's one sprag?
Could there be something else that went to cause every gear to go out? (Automatic Tranny)
I am thinking about getting a whole different transmission, what would you recommend and why?
I am also going to be building a motor as long as I don't put too much into this transmission so if I did the motor how "difficult" would it be to pull the current motor and tranny at the same time then put the new ones in? ie would it be a two person job ect
Thanks for your comments and ideas!
**EDIT**
Possible Issues:
Input/output shaft?
Driver lugs on pump gears?
low-reverse clutch? (biggest lead so far)
I have a very interesting problem that needs to be solved. I have in my possession a 1986 IROC-Z with a stock 305. Here is where the mystery comes in. I drove my roommate to his class. I stopped at a stop sign then took off. The RPMs got no higher then 2.5k. Then I heard a bang and I lost power to the rear wheels. I didn't beat on her that day at all. I got it towed to the auto shop and they said the transmission is the issue but they didn't tear into it to see what's wrong.
Issue:
-Accelerated from a stop sign heard a bang and then no power to the rear tires.
-Wasn't beating on it.
-All gears are gone.
-No slipping or anything before the total loss.
-A sprag on it did break last spring and the warranty covered that, but now the warranty is over (as of September last Fall two days before it had a meltdown).
Before someone mentioned it could be the other sprag going this time, but my question is why did forward and reverse go out at the SAME time if it's one sprag?
Could there be something else that went to cause every gear to go out? (Automatic Tranny)
I am thinking about getting a whole different transmission, what would you recommend and why?
I am also going to be building a motor as long as I don't put too much into this transmission so if I did the motor how "difficult" would it be to pull the current motor and tranny at the same time then put the new ones in? ie would it be a two person job ect
Thanks for your comments and ideas!
**EDIT**
Possible Issues:
Input/output shaft?
Driver lugs on pump gears?
low-reverse clutch? (biggest lead so far)
Last edited by Shane4524; 04-10-2013 at 02:55 PM.
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Car: 82 S10, 83 280ZX, 84 Z28
Engine: 355 smallblocks..na, 2.8 turbo
Transmission: 85:th350, 84:700R4
Axle/Gears: 85:ford9 4.85, 84:stock 3.24
Re: 700r4 Transmission Meltdown
Could have stripped the splines in the converter.
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Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: 700r4 Transmission Meltdown
So something broke
Quite simple
You either broke a input part ( the convertor , pump , input shaft ) or a output part (output shaft ) disabling the whole trans
You either broke a input part ( the convertor , pump , input shaft ) or a output part (output shaft ) disabling the whole trans
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: 700r4 Transmission Meltdown
The first auto place I hauled it to said that the converter was fine, that was my initial thought.
Seems like we have it narrowed down to the pump gears or the input/output shaft. For clarification, what are the pump gears?
Also, for the input versus output shafts, would there be a way to tell which one it is? When i put it into any gear nothing happens and I hear nothing, so something completely stripped or what not along those lines.
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Car: Pontiac 89 GTA
Engine: 350 TPI 5.7L V8
Re: 700r4 Transmission Meltdown
I'm no expert at all but is sound like you are ether in neutral or park all the time so i'll check the cable that move the lever in the tranny side to see if it broke or is loose.
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Car: 1986 Camaro IROC Z28
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Re: 700r4 Transmission Meltdown
Ha. I would kick myself if that's what happened. But, the cable did come loose before and I had it taken care of. And I can tell it is still connected because you can feel the difference between it being connected and not. It could also be in that area though. The cable could still be connected to the transmission but maybe the bang I heard was it snapping just on the inside and then it slipped into neutral. I can still push the car so it can't be in park.
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Car: 82 S10, 83 280ZX, 84 Z28
Engine: 355 smallblocks..na, 2.8 turbo
Transmission: 85:th350, 84:700R4
Axle/Gears: 85:ford9 4.85, 84:stock 3.24
Re: 700r4 Transmission Meltdown
Well Yes, that is the general consensus and that is why I am asking for help on here. I know it is broken. I'm just trying to learn and see if we can solve the problem without having to pay hundreds for someone else to figure out the problem. If we can narrow it down to a few things or one thing then we have somewhere to work from instead of looking through the whole thing.
The first auto place I hauled it to said that the converter was fine, that was my initial thought.
Seems like we have it narrowed down to the pump gears or the input/output shaft. For clarification, what are the pump gears?
Also, for the input versus output shafts, would there be a way to tell which one it is? When i put it into any gear nothing happens and I hear nothing, so something completely stripped or what not along those lines.
The first auto place I hauled it to said that the converter was fine, that was my initial thought.
Seems like we have it narrowed down to the pump gears or the input/output shaft. For clarification, what are the pump gears?
Also, for the input versus output shafts, would there be a way to tell which one it is? When i put it into any gear nothing happens and I hear nothing, so something completely stripped or what not along those lines.
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: 700r4 Transmission Meltdown
Perform a line pressure test then post up your results. I will tell you where to go from there. You could pull the pan and see if there are parts in the pan. Something could still be broke inside the tranny and not have pieces in the pan. So a line pressure test will tell you the pump pressure in each gear.
So as soon as I figure out some more info I will give an update on here.
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Car: 1986 Camaro IROC Z28
Engine: 5.0L 305 TPI
Re: 700r4 Transmission Meltdown
I met with a Mechanic who had rebuilt 700r4 for the past 30 years and worked at a Chevy dealership. He definitely knew his stuff. He showed me diagrams, pointed stuff out, and I think he found my problem. He mentioned the low-reverse clutch. He specifically said when they go there is a bang. This was before I told him that I heard a bang when the tranny stopped working. Now it is to decide if I want to keep messing with this 27 year old tranny that has been opened up several 3+ times or if I should go for a different one. He did mention him having a bunch of 700s laying around so I may go that route.
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Car: 86 IROC
Engine: 5.0 TPI
Transmission: 700-R-4
Axle/Gears: 2.73 open
Re: 700r4 Transmission Meltdown
I met with a Mechanic who had rebuilt 700r4 for the past 30 years and worked at a Chevy dealership. He definitely knew his stuff. He showed me diagrams, pointed stuff out, and I think he found my problem. He mentioned the low-reverse clutch. He specifically said when they go there is a bang. This was before I told him that I heard a bang when the tranny stopped working. Now it is to decide if I want to keep messing with this 27 year old tranny that has been opened up several 3+ times or if I should go for a different one. He did mention him having a bunch of 700s laying around so I may go that route.
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Car: 1991 Pontiac Trans Am
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3:42
Re: 700r4 Transmission Meltdown
My advice buy a prebuilt trans with a warranty. I rebuilt my trans just so the valvebody can seize up from gunk and smoke my fresh built trans.
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