TH350 vs TH375b

[Maine1]

ive never heard of TH375b till the other day i found aTH350 for a good deal suppossed shift kit and alto bands for good deal from this engine builder whos just getting rid of stuff but hes taking all day to get back with me on the trans and is hold up completion of my project so i end up finding this guy with TH375b looks just like TH350 short tail he says its a beefed up version of TH350 it has fresh rebuild and shift kit like the TH350 im trying to get question is will this trans rob power like a TH400 and are they better than TH350 really or just another GM experiment that went wrong both are going for the same price

[ProPower engines]

It may be for the newer vehicles that use a lockup converter. They did have issues with converters and pumps.
The older TH350 is a better choice if you will beat on it.

[nabx22]

tification
The 400 transmission has a main case of cast aluminum alloy with a length of 24-3/8" long. Its aluminum case is essentially smooth. The rear mounting face of the transmission has a hex bolt pattern with ribs running forward longitudinally. The fluid pan shape is irregular (see image, left), being likened unto a distorted Texas pattern. The TH400 is the largest of the common GM auto transmissions, but still surprisingly compact in light of the immense power they can handle.
The TH400 and Jeeps have quite a history together. This list is of the Jeep powertrains that had this excellent transmission. The TH400 came in 2wd or 4wd Jeeps, coupled either to the popular Model 20 transfer case or the Quadra-Trac, the latter being an option from 1973 to 1979. The early versions had factory block adapters. Later AMC versions had their own case with no adapter.

1968-1971, 350 V8 (Buick)
1969-1972, 225 V6 (Buick)
1972-1975, 232 I6 (AMC)
1975-1979, 258 I6 (AMC)
1972-1979, 304 V8 (AMC)
1972-1979, 360 V8 (AMC)
1974-1975, 401 V8 (AMC)
There are two significant variations of the TH400. The TH375 was a version of the transmission used from 1972-1976 in smaller displacement cars. It is identified easiest by its "375-THM" designation cast in the underside of the tail housing. The TH475 was an extra-heavy-duty version, and was found in larger trucks from 1971 on.
If you are trying to determine the TH400 from another in a vehicle, a fast way to tell is to look at the kick down mechanism. The TH400 uses an electrical slide switch, which is controlled by the throttle linkage. The TH350 uses a mechanical cable kick-down mechanism that is attached to the throttle linkage.
An interesting variable pitch stator feature of the Turbo 400 was available in 1965-1967 Buick, Olds and Cadillacs. These are identified by the two-prong plug on the case. While 1970-1974 models also had this plug, it is for the transmission controlled spark system.

[Baprace]

ive never heard of TH375b till the other day i found aTH350 for a good deal suppossed shift kit and alto bands for good deal from this engine builder whos just getting rid of stuff but hes taking all day to get back with me on the trans and is hold up completion of my project so i end up finding this guy with TH375b looks just like TH350 short tail he says its a beefed up version of TH350 it has fresh rebuild and shift kit like the TH350 im trying to get question is will this trans rob power like a TH400 and are they better than TH350 really or just another GM experiment that went wrong both are going for the same price

The Turbo375 uses many T400 parts, the outputshaft is the smaller size but oil pan,valve body, case, pumps,drums are mostly T400 pieces and it uses a T400 modulator upfront on the passenger side with an electronic kickdown.

[Alan Roehrich]

A THM375 is a TH400 with a medium length TH350 output shaft.

There is a TH350 that was designated a TH375 (note the lack of the "M", TH375, and NOT THM375), it is merely a TH350 with a few minor upgrades.

[Schurkey]

375 = light-duty 400. Fewer clutch plates, smaller output shaft (same spline count as a 350)

375B = heavy-duty 350. More clutch plates, maybe other internal parts are stronger. Same output spline count as a 350.

The "B" makes all the difference.

A 375B would be an EXCELLENT choice for any application where a 350 is being considered; and strength is a concern.

The lockup clutch version of the 350 is the 350C.

If there's a difference between Turbo-Hydro and Turbo-HydraMatic (TH vs. THM) I think it's purely in the mind of whoever is writing down the initials.

[rfoll]

I have a THM 375 that was given to me. I have been hanging on to it for THM 400 parts, but I am starting to wonder if there is anything of value inside.

[Alan Roehrich]

The drums will hold fewer clutches, and the direct drum will have the low capacity roller clutch as opposed to the 34 element HD sprag. But it is still a good core, you can make a regular 400 out of it with the correct output shaft and extension housing. The drums can be changed.

[Maine1]

yeah the trans is TH375b not 375m it feel heaver than the TH350 i have over heaver but will it rob power like a TH400

[Schurkey]

yeah the trans is TH375b not 375m it feel heaver than the TH350 i have over heaver but will it rob power like a TH400

The 400 does not "rob" power any more than any other automatic trans, except that it has considerable rotating weight. For MOST vehicles, this is simply not a concern. It won't show up on the timeslips.

For VERY quick cars, the additional inerta of the 400 may begin to affect quarter-mile times. But by then, you've got cubic dollars in the engine; so cubic dollars in the trans and rear end is to be expected.