The first year (1964) was a little bit of an oddball as you could not manually select second gear. I have a fresh one on my bench (nailhead pattern) and not sure what I am going to do with it.
The t400 is a beast and can be made ridiculously strong, but the thing i dont like about it is the reversing of the sun shell during the 2nd to 3rd shift. It also has much more hp loss than the t350. I'd prefer a built 350 in anything less than 2800-3000lbs, unless there is big power and big traction involved. I was pleasantly surprised that its not a ton heavier than a t350. I usually play with 727s and they weigh alot. -rick
Not sure what you mean by "reversing of the sun shell". In 2nd gear the sun gear is held stationary then accelerated to input shaft speed in 3rd. It works exactly the same as a 350, a 727, a 904, a C4 or a C6. They all have the same basic gear set. Do you mean there is no engine braking in automatic 2nd gear meaning that the sun gear shell is allowed to rotate clockwise? The 350 works the same way. If you let off the throttle in automatic 2nd gear, the transmission just shifts to high where you do have engine braking.
The best tough transmission, I have one behind the blown big block in the 41 and one behind the small block in my 57 p/u I plan to tow with, then there's one I just had my son build as a backup for my 51 Henry J
The input shell does not reverse. Because the forward clutch and the high/reverse clutch are both applied and form a direct output the input shell which is keyed to the high/reverse clutches stopped the independent rotation of the input shell. Thus locking the high/reverse clutch and forward clutch together, producing a dir3ct output giving high gear. I taught automatic transmissions for 15 years in a vocational class. I used a C4 parts group to demonstrate the operation in open class and used C6, Th350, and Th400 transmissions to small groups once they understood basic Simpson transmission function. I had many guys graduate and be successful automatic transmission mechanics. As a humorous aside, I taught bumper to bumper and had a student come in the class and told me that all he really wanted to learn, was automatic transmissions. I told him that he must participate in all of the class activities, but was welcome to use his free time to study automatic transmission as he wished. So, he spent lots of hours researching Ford, GM, and Chrysler automatic transmission manuals on his free time. I came by and he would be taking copious notes on each manufacturer's transmission. I offered my help, but he said that he was learning okay as is. When the class got to the automatic transmissions course and found out that almost all automatic transmissions operated exactly the same, with each manufacturer having a different name for almost every item in the transmissions even though they were really the same design he came to me and said that he wished he had listened to me I in the first place. There is alot of macho involved in the auto industry and all 3 major manufacturers will have a different name for the same transmission part. Back in the dark ages when I learned, my instructor taught us by function and not by what a certain company called something common in all auto transmissions. It sure helped me, and I know it helped lots if my students figure out that automatic transmissions weren't that scary, and were designed and built by regular people.
Thanks for the explanation. I have a ST400 in my car with a shift kit, I have no engine braking when I down shift to 2nd. Everything else works fine on the upshift. Any ideas here.
Nice video. When I taught automatic transmission repair, I had a Storm-Vulcan dyno. It was an enormous machine with a variable speed belt drive. It was designed some time in the 50's. It had an input and output speed and I think 6 pressure gauges. It also had a vacuum pump and a tank that held 55 gallons of ATF. The dyno in the video is very nice.
Building and running Pontiacs most of my life I always went with the 400. Tough Trans and with a shift kit along with a torque converter they made a killer setup. ...
there is nothing wrong w running something that is solid with no electronic s in them unlike these newer transmission s
Have had a 400 turbo behind a blown injected 392 hemi in my avatar car for 20 years. Still going strong.
Tell me more about this. I’m running a TH400 that needs an OD. I thought gear vendors or a 700r4 were my only options.
I’ll add some TH400 trivia that my save you a headache in the future: from the beginning to about 67 TH400s had a smaller tail shaft seal. I found out I have an early one when trying to get a little extra length out of the driveshaft but buying a longer slip yoke. Well, they only make longer slip yokes for the later, more common 2.7” seal. So my fix was buying a new tail shaft housing from Summit for $100 with the more common larger seal and slip yoke. Just FYI.
It’s an add on OD. Bought one from Marketplace a few years ago. Bolts in place of the tail shaft like a GV. It uses a 2speed rear end motor and switch to operate.
I had an OT car with a TH350 behind a 427 BBC and the trans needed a rebuild. I took the car to a trans guy and asked him to build me a TH400 that could be used for street and strip, and he told me he could build the TH350 to be plenty strong for the engine. Let him do his thing in 1982, and when I sold the car in 2015 the trans was still in there, and still working great. Just did a service on my late 60's Chev Suburban 2 days ago as the pan gasket began dripping. Dropped the pan and did filter and gasket, and the magnets in the pan had almost no metal powder on them. It's a TH400 and has always been my tow rig, and daily driver/hauler for many years. I have a built TH350 manual shift kit in my Austin gasser, but went to a well built 700R4 in my '39 Chev gasser so I could take it on long trips. I think both trans are great, and have proven themselves as reliable transmissions.
That was originally made by Doug Nash. The design was later sold to US Gear. They were made in both overdrive and underdrive units. Either can be used so long as they are paired with the correct rear end ratio. While they do not have the same HP/torque rating as a Gear Vendors overdrive, they work well.
There was a 375 also that had a smaller output shaft. I want to say it was the same size as a 350. The output shaft was the same size, the trans was the same as a 400
I believe the 375 has a th350 spline on the output shaft whereas the early small diameter th400 has a 400 spline.
I purchased two 1963 Grand Prix’s late last year and have been driving one of them with the Slim Jim” roto-problamatic transmission in it. The car runs ok after sitting for 35-40 years but the shifting of that transmission is annoying at best. I find it interesting that GM saddled Pontiac and Oldsmobile with one of the worst automatics ever built, and then just a few years later replaced it with the best automatic transmission ever made.
We had a version of the Slim Jim in GM Holden vehicles as their first auto in 1961. Lasted through three vehicle models (EK, EJ and EH) until we got the 'Glide for the HD Holden in 1965. Cheers, Harv
I would imagine the Slim Jim was not a good transmission of choice for some of the more remote areas of Australia. There are probably many thousands of these that have been sent to the recycling yard or are waiting on that same fate while gathering dust under someone’s garage bench. I plan to replace mine with a TH400 in the next month or so, still working on the adapter plate and gathering a few items.
We were fortunate (if you can call it that) that GM Holden didn't over-tax the power going into the gearboxes. The hydramatics were only put behind 138ci "grey" motors (75bhp), and 149ci/170ci "red" motors (up to 115BHP). We didn't see a V8 until 1968, when we imported 307 and 327's to run in the local HK Holden assembly. Cheers, Harv
I walked into a beer cave other day, so many choices, bright colors, felt like I was in a calidioscope... took me 20min to pick Corona, got home, and I'm out of limes.
The Jalopy Journal
