TH-400 Question

[zodiacblue442]

Does anyone know how to get firmer shifts in a TH-400 (without installing a shift kit)? I seem to recall hearing somewhere that if you turn an adjustment screw someplace it will make the trans. shift firmer :confused: The guy that rebuilt my TH-400 about 7 years ago in my 442 did a great job. He was a transmission mechanic at a Chev. dealership for decades. He built the trans. "stock." Like I said, he did a terrific job, but the trans. shifts "soft" (especially on the 2nd to drive upshift). Feels more like a trans. out of a 98 Regency than a 442. I'd like to firm it up a little. Any help would be much appreciated! Thanks! :)

[73CS]

Have read and talked to guys (Olds guys) that use the ford type F trans fluid, they say it thicker and has less slip, I have not personally tried it, anyone else used this?

[76HOProposal]

erased

[442MUCH]

Hi Gary, I also wanted quicker shifts and went the shift kit route. My transmission was rebuilt in 1992 and I paid to have it guaranteed for life (thank goodness). They installed (at my request) a Transgo Shift kit and if I put my foot into it, I get rubber in second gear with out shifting. On occation, I can get it to chirp in third if I shift. On a wet road, she breaks loose going into 2nd and 3rd (with your foot into it). Otherwise you just feel the shift under regular driving.

I went with a Transgo because I had read that they were the best. Bob seems quite experienced in this and he seems to agree, so I'm glad I made that choice years ago.

[zodiacblue442]

Thanks very much for the info. That's interesting about the leaking trans cooler in the side tank. When I restored my 442, I replaced the original radiator with a brand new Modine. I'll keep the shift kit in mind for a winter project. The vacuum mod. screw is what I was referring to. I do 99% of my own work on my cars as well so installing it won't be a problem. I agree that one really has to be careful when someone else works on your car.

To follow up on the other post, I don't claim to be a bodyman, so I had that work done and didn't get my money's worth. The car looks gorgeous, but there is evidence starting to show that the bodyman didn't correctly repair the isolated rust areas in the rear quarters. The car has been in about 6 rain storms and washed maybe a couple dozen times in the last 7 years, so it's not exactly been abused. It's never seen winter snow/salt since it's been restored. The car is garaged all the time and parked from Oct. to late April. The humidity here in CO is usually only around 10%. I still get to deal with rust issues again down the road. I do my own engine rebuilding, but had a machine shop do the necessary machine work. The engine failure was an out of round connecting rod, thanks to the machine shop not reconditioning the rods right. No. 5 rod was the worst one. Funny thing is it plastigauged within spec. It was obvious it was out of round though after the failure looking at was was left of the bearing and the crank journal.

Thanks again for the information! :)


Gary,

Unlike others, I do most all the work on my own cars. In this day of poor care and service one has to. You never know what you are going to get even with all the dialog that transpires before hand. (I saw your other post on the subject of work done for you.)

The screw you are referring to, I think, is in the Vacuum Modulator. That adjustment only can be done correctly if your car has an adjustable one. (Oh I've heard of the stories of people adjusting the factory's stock Modulator. But I've heard of even more stories of torn rubber Modulator diaphragms of those trying doing to do the same.) It will only delay your shifts or make your shifts sooner. Which now that I think about it, can make the trans. shift a little harder. Because of the slight increase in line pressure at a higher RPM.

For the problem you describe I would recommend the TransGo THM 400 Shift Kit. (Hey if you can change your trans. filter and fluid you can install one!) Their kits are well thought out and copied by all the other aftermarket companies. So much that they now have patents.

Please also note that the 73s had a Oldsmobile factory campaign where the trans. cooler was replaced inside the radiator side tank. The cooler would leak , mix ATF with coolant and because of the water soluble clutches inside your trans. it would fail. So Nice. I had it happen on my 73 Hurst Olds. Most dealers wouldn't change them unless your trans went out. And they usually never told the customer that there was a campaign. A friend of mine in Olds service let me know and I paid nothing at the time. Quite a savings for me at the time. Just a thought for you.

[zodiacblue442]

In drag race cars, I know some guys run Type F fluid in their TH-350's and 400's because it's more "abrasive" and gives more positive shifts - doesn't let the clutches slip. It's harder on the clutches though and causes the clutches to wear faster. My personal opinion, I'd stick with Dexron in a street driven car.


Have read and talked to guys (Olds guys) that use the ford type F trans fluid, they say it thicker and has less slip, I have not personally tried it, anyone else used this?

[GT73]

I agree with Gary, stay away from using F Type tranny fluid.

If you don't install the TransGo shift kit (set it at stage 2 for street cars) then at least get an adjustable modulator (runs on vacuum) so that you can adjust the shift points (2-4 mph). Hurst sells them... http://hurst-shifters.com/catalogpdf/1-Automatic-Shifters/Access1.pdf

Also, its a good thing to have the tranny checked internally for any worn plates. I know cause I just went through this entire ordeal of trying to improve the shifts on my '73 Cutlass Supreme with a modified 455 Rocket. The car will now chirp from 2nd to 3rd under full throttle using a 10 bolt posi rear with 3.42 gears.