Does anybody know if Hurst made any changes to the 72 H/O turbo 400 tranny during their conversion process? Such as changes to the factory valve body or removal of check *****? Mine shifts hard as a rock and I love it. But it's making some noises like I've never heard before and I don't want to mess that up with the wrong rebuild kit (gaskets/springs/bearings/wavy clutch plate replacement etc). My hope is all I need is a pump rebuild. Thanks

 

What kind of noises? I wouldn’t be surprised if the Hurst cars got special transmission calibrations, but they would still need to be civilized enough for the general buying public. While performance enthusiasts appreciate the “bang/screech” shifts, 95% of new car buyers won’t. Sounds like your can has had a shift kit installed somewhere in its past.

A TH400 with a regular auto shifting valve body will work with only 2 check *****. The others are used to control the rate at which clutches/bands apply.

Remove the transmission pan. The debris and crud in the bottom of the pan will tell you what you need to do. Hopefully all you will find is some fine silty debris, the normal end result of friction/thrust washer wear. If you see big chunks, or enough crud to support farm crops, then chances are your transmissions days are numbered. If it works ok, replace the filter with one than has the brace screen instead of fiber filtering media. Some shops call it a Allision filter.


If you do need the trans rebuilt, just tell the builder to reinstall the valve body/spacer plate as is. Tell him you like the shift the way it is, just don’t like the noises it makes. If he argues, build it yourself. If your comfortable building an engine, a 400 trans is pretty easy.

 

Thanks Matt. I wish I could describe the noise. Maybe a clunky scraping type noise along with vibrations that are intermittent. I've listened to failed torque converters on u-tube and it's not a squeal or continuous whine. But it does only happen after things warm up say 20 minutes of driving or so. And you can feel it through the car to the point where I thought the trans was just going to come apart internally. I like the idea of just reusing the valve body/spacer plate as is. When I got this car back together and started it after about 17 years of being in pieces, about the first 20 starts or so the trans made a whining noise and I just figured it was the pump. That noise stopped and I drove the car for the first time without any problems.

 

I can tell you they made changes to the TH400s in the '69 H/O's, so it is possible. You might try reaching out on the Hurst Olds Club of America Facebook page, lots of knowledge there.

Good luck!

 

The 1969 H/O used a TH400 that was unique to that application, with it's own OH designation. No other Olds used an OH trans in 1969.
The 1972 H/O used the same OD trans as did every other car with the L75 motor that year. The handful of 72 H/Os built with the L77 W30 motor got the OW trans just like every other AT W30 that year.

 

I have never seen literature on the hurst Olds trans, so I cant speak with any certainty. I do know the Ow and BB used a unique valvebody calibration with A special 1-2 detent valve. They also had special direct drums that accept 6 friction plates (no wave plate) no spring in the 2-3 accumulator, and a special governor.

You may find this interesting. I have been searching for this valve body calibration for several years.

http://www.buickperformanceclub.com/SPTrans.htm

 

Drop the transmission pan. If there is anything wearing or damaged, you will see the evidence in the pan and filter. If everything looks good, look elsewhere for your noise.

 

Great link, thanks for providing that.

 

Your welcome. I thought that was an interesting article. While the basic TH400 hasn’t changed much over the years (other than production/engineering changes) I didn’t know there were that many different calibrations and spacer plate variety. I’d love to see some engineering sheets outlining what valve bodies got what valves and springs.

It pains me now knowing I probably scrapped a few hundred of those valves/sleeves I’m searching for now when I worked at Coan. One of my jobs was tearing down valve bodies in preparation for machining. I would typically tear down 100 valve bodies at a time for transbrake, reverse manual, and the pro tree transbrake.

 

Pain? In 1979 I had a 69 Camaro with a 402 I had put in it. My buddy had a 72 Hurst/Olds. I laughed at a sticker in the engine bay that if I remember correctly was on the radiator core support or fan shroud that had numbers on it that also contained W30 300HP. Told him we had to change that. I bought a cam, aluminum high-rise and Holly carb and tore into it. He met a girl and disappeared from sight. I finished the build and he sold the car for $2,000 which was more than I could afford at the time. The next time I saw that car the front end was bashed because the setup wouldn't make enough vacuum to allow the brakes to properly function. Never saw the car again. Ouch!!! That still hurts today.

 

Identified! The noise and vibration was from the bushing on the output shaft of the Gear Vendors OD. My driveshaft was 1& 3/8 inches too short and the yoke wasn't seating properly and the bushing became ruined. Trust your own measurements guys! Gear Vendors gives detailed instructions with the OD unit on how to size your driveshaft. My local driveshaft shop I used based their shaft solely off the length of the original driveshaft. Said they knew what they were doing. Won't call them out, not my style. I should have questioned them when my number was not their number. Nice new aluminum shaft from my new driveshaft guy was only $650. GV rebuild kit $42.50.-Just love spending money twice on the same thing right.

 

Glad you found it, but FYI, nowhere in this thread did you tell us that you have a GV in the car. The mind reading thing still isn't working. It's kinda hard to give useful info if you don't know the details.

 

True Joe. I've been chasing this drivetrain vibration/noise thing for awhile now. Had a thread on the rearend where I ended up replacing the pinion bearings. Noise reduced but still vibration after that so I turned to this transmission thread thinking I should just focus on each component one at a time. Finally took the car to a shop with a dyno so that I could observe the drivetrain under load. Would never have suspected the Gear Vendor unit as it has less than 250 miles on it. All caused by an incorrect driveshaft length. I haven't done a test drive yet so keeping my fingers crossed. Should know if problem solved by this 62 degree Saturday we're supposed to get in Cincinnati. As always thanks to all who took some time to help me out! Merry Christmas!

 

I thought I would add this to this old thread. Don't know if anyone will see this but....We all know sometimes what we think is the problem never is. I finally found the cause of the vibration my butt was feeling. When my drivetrain would heat up the 2 top studbolts securing the nosecone on the overdrive would lose their clearance and butt up to a support brace on the underside of the floor pan (aftermarket A-body full floor) that I had installed. I lowered the trans down, saw the gouge marks and then cut about a quarter inch off the 2 top studs. Like riding on a soft puffy cloud now. Again, thanks to everyone who took the time to help me out! Having fun at local events now.