Broken C4?

[flexmerc]

here we go....
just recently completed an engine swap, and was dialing in the Holley Sniper EFI. I have regear (4.56), and a rebuilt D20 (hermtheoverdriveguy), Gear star C4, that I've been running now for over a year, and the engine was the last mechanical piece I wanted to do. I have always kept the Bronco running, throughout all these changes.

Well during my third test drive post engine swap, the bronco just didn't have the get up that it had before...it felt sluggish and I was chasing AFRs/Timing; and during an hard acceleration a very loud and aggressive clunk shook the truck and now it will not drive, I had to call the wife to tow me back to the house in my truck (yes she took a picture of me on the side of the road).

Shifter linkage is solid, and the tranny is shifting through the gears, just not engaging. I also double check the t-case, no issues there.

Any thoughts?

 

[Broncobowsher]

Does it buzz when shifting into park with the engine running?

 

[flexmerc]

No buzzing, shifts like normal and I'm unable to push the vehicle while in drive...but it will not move with throttle input.
While in neutral the vehicle will roll forward and back.

 

[Viperwolf1]

Did the tcase pop out of gear?

 

[flexmerc]

nope, slipped it out into Low and High, and did the same for the front...it has a twin stick.

No dice

 

[Big Ben]

Did the torque converter disconnect from the flexplate?

 

[73azbronco]

vacuum problem??

 

[Broncobowsher]

No buzzing, shifts like normal and I'm unable to push the vehicle while in drive...but it will not move with throttle input.
While in neutral the vehicle will roll forward and back.

So the transmission is 'locked' while the engine is running, You can load the convertor but feels like a brake is solid apply. But free to roll with the engine off.

Ignoring park position, does it do the same for all gear positions RND21? Only need to check running, off there is no hydraulic pressure and will all be the same.
It sounds like a clutch is stuck on. Either welded (transmission rebuild) or a valve body issue (probably a bit of garbage stuck a valve). There are a series of pressure tests to figure what is really happening.

 

[flexmerc]

Did the torque converter disconnect from the flexplate?

Negative, you can see the flex plate and toque converter in one of the photos

 

[flexmerc]

So the transmission is 'locked' while the engine is running, You can load the convertor but feels like a brake is solid apply. But free to roll with the engine off.

Ignoring park position, does it do the same for all gear positions RND21? Only need to check running, off there is no hydraulic pressure and will all be the same.
It sounds like a clutch is stuck on. Either welded (transmission rebuild) or a valve body issue (probably a bit of garbage stuck a valve). There are a series of pressure tests to figure what is really happening.

No, the trans seems to be shifting properly.
If it's in park, it can't move, neutral and it rolls.

I added a short video with it running through the inspection window

I double checked transfer case and tried front drive only, 4x4 low and high; only rear low and high...etc

It will not move; well I have a three year 36000 mile warranty, so I'm calling on Monday.
Their website says not to remove or make modifications until I troubleshoot with a tech on the phone.

 

[73azbronco]

bellhousing/case is cracked bottom, 4th pic on right. Yours or they supplied it?

So one hit I keep finding on c4 is vacuum problem could result in no tranny movement. Modulator good?

 

[flexmerc]

yes, I noticed that too, bell housing was supplied by gear star.
I check the modulator out

 

[73azbronco]

Yeah so that crack is not going to get better. I had crack like that same spot, had a speed shop weld it for me.

 

[flexmerc]

We'll see where we're going with this transmission on Monday. I have another bellhousing I can put in it

 

[flexmerc]

bellhousing/case is cracked bottom, 4th pic on right. Yours or they supplied it?

So one hit I keep finding on c4 is vacuum problem could result in no tranny movement. Modulator good?

So I used a known good vacuum modulator...I forgot how much trans oil comes rushing out!

Still no dice, I tried 4low, front low, rear low, 4hi and front high, rear hi...D20 seems to be operating and shifting fine.

I'll be on a phone call tomorrow

 

[flexmerc]

Keeping yall updated.

I called, Gear Star, I need to remove the D20. and see if I can see the Output shaft move while in gear.

MTF.
-flexmerc

 

[gnpenning]

Have you considered removing the inspection cover on the Tcase and checking operations first?

 

[73azbronco]

and rebuilt d20, hmmmm

 

[flexmerc]

Follow up:
I removed the D20, and with the engine running, and shifting through the gears, the output shaft was not turning.
so from the engine to input/TQ is spinning, but no movement on the output side.
I'm removing the trans and shipping it back to Gearstar, per their recommendation, so well find out more details in a few weeks.

 

[flexmerc]

I got the trans out, and prepped for shipping, some times this damn bronco is a full time job.
Any of you guys just want to drive it off a cliff to end the suffering of this addiction?

...Anyhow, there is the front input shift, it looks like the small end stripped the end a bit.
Engine, is 1987 302, bored out .30, with a comp 35-349-8, stock E7 heads and stock valvetrain.
Nothing crazy


Is this a common failure, did I screw up the TQ install?