[tooski]

When a trans goes bad how often would the internal structure of the trans be damaged.

I put a B&M shift kit set to street n strip in a TH350. Shifts were annoyingly harsh. Trans finally let go. Park n neutral are ok. All other gears are emulating neutral.

I do expect most of the responses would be to open it up and find out.

Frank M.

[242177P]

Which convertor did you use? Had a cheap
"Saturday Night Special" from TCI fail, same
results except it whined like a Powerglide.

[chiphead]

Typically when a TH350 has a hard part failure, it's often the intermediate sprag race. The direct drum is spinning at like 2/3 engine speed in first gear. The sprag stops the direct drum during the 1-2 shift, and takes all the shock load in doing so. The harsh chirp-type shift kits stop the drum faster than the stock calibration, so the shock load often causes the rollers to climb the inner ramps and kersplode the outer race. That usually results in the loss of 2nd gear, but it will still move in first and reverse. It may make crunchy noises while doing so. The case usually survives this.

Loss of all forward movement would be the FWD clutch, which is engaged in all forward ranges. Loss of reverse would be the Direct and low/reverse clutches, which gives reverse. If only low/reverse were dead, it would try to creep forward in reverse selection, through the direct clutch.

It could be as simple as the S link fell off the shifter's rooster comb inside, or something simple came loose in the VB, but unlikely. I've had that happen once, when I forgot a pin in the direct shift valve. The valve fell apart but didn't damage anything. I just lost direct and had to limp home and fix the VB.

Is it making any bad noises or low on fluid? The next thing to do is either put a gauge on the test ports, or drop the pan. With loss of all movement, I suspect malfunctioning valvebody, or dead clutches, or broken input shaft or broken torque converter. That's why I really dislike the harsh shift kits, they break stuff. I always use the Transgo 1-2 kit. Softer shifts, but will still break things if you do something stupid, like pedal the car on a nitrous pass..... Turning the nitrous on-off-on rolled the sprag and the drivetrain twist broke the bellhousing on the 1-2 shift!

[srmmmm]

Originally Posted by tooski

When a trans goes bad how often would the internal structure of the trans be damaged.

I put a B&M shift kit set to street n strip in a TH350. Shifts were annoyingly harsh. Trans finally let go. Park n neutral are ok. All other gears are emulating neutral.

I do expect most of the responses would be to open it up and find out.

Frank M.

I did the exact same thing in 1976. The transmission lasted about 6000 miles of tire chirping shifts from first to second and even from second to third at 85mph (Had a 2.73 rear end at the time). On a very important first date with my best friend's sister, I lost second gear. It was whiplash with every shift the rest of the night as it shifted from first to third at 4000rpm. Checked all the simple stuff the next morning: downshift cable, vacuum modulator and even pulled the governor to inspect for varnish buildup. Nothing looked bad and the fluid wasn't even burned. Dad said, "Better drop the pan". There was a handful of intermediate sprag rollers and cage fragments in the pan. That was a costly lesson for a 21 year old college student.

The transmission shop rebuilt it with a Trans-go kit including the 24 element sprag and that lasted almost 100,000 miles.