What did I blow up in my 727?

[440beep]

This past Saturday night I was out with a buddy of mine and his 70 Charger R/T and we were messing around on some back roads. He accelerated, and I followed suit and as I was accelerating, I was overcome by stupidity, and downshifted from D to 1 (with my 727). For a split second, the car accelerated then a loud bang and no more going. I gave the car some gas but it just continued coasting; had nothing in D, 2 or 1. Got to the side of the road and started looking. There was no fluid pouring out, fluid was still red and saw no metal shavings on dipstick. While being tow strapped to my buddy's house, a whining noise could be heard in N. Car still moves in R. And this is a 727 built by a reputable Mopar transmission guy, so kind of sad this happened. Really hope that whatever is blown up, it's not the GearVendor OD.

Learning my lesson never again to downshift from D to 1 while accelerating, I'm assuming I need to drop the trans and have it rebuilt, as it's probably more complicated than just the valve body or something accessible with the pan off.

I'm doing my learning now, so what most likely did I blow up?

 

[toolmanmike]

Probably a sprag. Time for it to come out and get repaired. They have billet sprag and planetaries that are much tougher than the oem ones.

 

[WileERobby]

Check all the linkage, but you might have a blown sprag.

 

[451Mopar]

When I did that, the transmission survived, but several engine valve got bent.
As mentioned, most likely the sprag, rear band and/or rear band servo?

 

[Photon440]

I've had a blown sprag, but it still moved forward when in position '1' because that would apply the rear band as well.

 

[twecomm]

My 66 Chargers 727 was going strong with no issues. But nothing lasts forever..
One day at a traffic light, at the 98 K mile mark, went to accelerate after light changed and a strange crunching noise and a bang from the tranny. Then, almost no forward motion at all. I shifted around and more grinding noises were heard as I tried to move. Managed to limp home since I was not more than 2 miles from home. Went to go up driveway but no forward motion at all possible however reverse was fine. Backed up driveway into garage, checked tranny fluid levels, OK no smells. Next morning found a repair shop that guaranteed me that car would be kept on the lift indoors until repaired. Had car flat bedded to the repair shop. They had many lifts in this place. A big plus was that the owner of the repair shop was also a classic car guy. They did a full rebuild on the 727, plus new torque convertor. Came with a great warranty on the repairs. Now it shifts better than it ever did.

 

[Ron H]

You'd have more fun with a manual. I'm no trans expert other than having done work on them on the car such as installing a shift-kit and adjustments; but was informed long ago that it was not a good idea to do harsh downshifting. You can manually upshift all day..

 

[Dipstick]

I'm thinking if it were the sprag, it would still move forward in 1 but not in D or 2. Could be the front planetary. Does it still have reverse?

 

[440beep]

Yes, reverse still works. D, 2 and 1, no movement whatsoever.

I'm thinking if it were the sprag, it would still move forward in 1 but not in D or 2. Could be the front planetary. Does it still have reverse?

 

[66 Sat]

Does shifting from D to 2 at between 2,000 and 3,000 rpm and then nailing the throttle also count as bad for the transmission? I do this all the time. I also drop to 1 when accelerating but that's less often.
I didn't realise I was potentially doing damage. Is there a safer way of doing this - full throttle alone doesn't always kick the transmission down (depending on the revs) and then it changes up again before I want to change (usually at 5,800 rpm).

 

[Ron H]

Experts here could let us know. High rpm neutral drops and wicked downshifting, as I was lectured anyway, was unwise with a stock trans. I have a ’63 727 PB trans that’ll shift to 3rd gear around 25 mph – unless under full throttle. These older trans didn’t have partial throttle downshifting unless flooring it. When I tromp on it anywhere after it shifts to 3rd and maybe up to around 60 mph or so, there’s a real kick in da butt downshift; but after this it won’t. The shift kit I put in does give a harsher shift; but didn’t go all out with it having a choice on the setup.

 

[Dipstick]

Does shifting from D to 2 at between 2,000 and 3,000 rpm and then nailing the throttle also count as bad for the transmission?

That seems to be one of two ways to strip the splines out of the front planetary. The other way is a 1-2 shift under full power.

 

[dvw]

The sprag (low roller clutch) will not disable 2nd and 3rd. It either broke something in the rear clutch assembly or stripped the front planet splines.
Doug

 

[440beep]

The Bee is up in the air, and dropping the trans/Gearvendor tonight. Though I still need to run out and buy another jack for tonight, one jack to support the motor, and one to lower the transmission. Also needed higher jack stands, so I searched the posts here, and picked up 2 sets of the US Jack 6-ton stands and being very close to Benton Harbor, MI, the jack stands were here in a day. As someone said in one of the posts, "how valuable is your life?" There's always a part of me that is hesitant getting under a car even with the wheels on.

Luckily I'm very close to Keith Long (727specialist.com) who will be doing THIS rebuild. After learning about the Griner valve body, I'm very interested to see if I notice any difference in the shifting.

 

[Moms68]

Fun is.....the top bell housing bolts are a joy to get to.

 

[Dipstick]

Attack the top bolts from the rear with a 4-foot long 3/8" drive extension with a 9/16" swivel socket.

 

[451Mopar]

Attack the top bolts from the rear with a 4-foot long 3/8" drive extension with a 9/16" swivel socket.

https://www.amazon.com/GearWrench-84917N-Universal-Impact-Socket/dp/B00UM687VG

 

[66 Sat]

The Bee is up in the air, and dropping the trans/Gearvendor tonight. Though I still need to run out and buy another jack for tonight, one jack to support the motor, and one to lower the transmission. Also needed higher jack stands, so I searched the posts here, and picked up 2 sets of the US Jack 6-ton stands and being very close to Benton Harbor, MI, the jack stands were here in a day. As someone said in one of the posts, "how valuable is your life?" There's always a part of me that is hesitant getting under a car even with the wheels on.

View attachment 1174917 View attachment 1174918

I'm sure that set up is safe, but I'm like you in that I hate getting under cars when they are in the air.
I'd put a stack of hardwood blocks under the frame rails too, wherever I could that would still allow access. Just as extra insurance.

 

[440beep]

Transmission is out safe and sound. My mechanic buddy, who has the 70 Charger R/T, came by to help me get out. No way that could be done solo, especially with the OD unit on it. And headers suck!!! when you have to work on the car!

 

[StrokerSpanky]

It's either the forward clutch or the front planetary gear carrier or forward ring gear. Chrysler calls it the front annuls gear but same thing.