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)

 

Could have stripped the splines in the converter.

 

Or broken the drive lugs off the pump gears
Did that several times back in the day on my TH350 with the stock style powered metal gears until I installed billet steel pump gears
Problem solved

 

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

 

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.

 

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.

 

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.

 

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.

 

I am currently away at college so I cannot do the line pressure test til I am with the car next Saturday. I will be calling the auto shop this up coming week to see what the deal is. They did mention about at least taking a look at it even though it is past the warranty. So i will see where they stand and may just have them do the pressure test. I will also be going around the town I am currently in and asking the auto shops their opinion and I will post their feedback also.

So as soon as I figure out some more info I will give an update on here.

 

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.

 

the main thing is that your trans case is not damaged ,you can rebuild it indefinitely if it is ok

 

If you decide to end up using another 700r4, try to get a 1988-1992 700r4. They're a lot more durable than the earlier ones. GM was still working the bugs out of them in 1986, and didn't really get them right until around 1988 or so.

 

anyone check to see if the driveshaft is turning?? raise up the rear wheels and put it in gear -- I have seen a few that break a rear diff and car won't move. Does it hold still in park?? (just thoughts)

 

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.

 

http://www.700r4l60e.com/

 

yep, when you don't get everything clean (cooler in the radiator) and go through the valve body, that can happen.....