Original automatic behind 305

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Original automatic behind 305

Postby kgroombr » Sun Sep 20, 2015 9:44 pm

A friend and I were discussing the available automatics that came behind a 305 V8 in Monza's starting in 1976. I have never seen anything other than a TH200s in 76s and later, but he insists that the TH350 was an option. I googled a bit and found nothing to say either way.

Anybody know for sure?

Thanks,
Ken
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Re: Original automatic behind 305

Postby monzacoupe » Sun Sep 20, 2015 10:07 pm

Found this from Bryan's website. http://monza.homestead.com/files/MonzaP ... umbers.htm

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Re: Original automatic behind 305

Postby marco_1978_spyder » Mon Sep 21, 2015 7:39 am

I can confirm, the 78 and 79 used the the TH350 behind the V8. 76-77 TH200.
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Re: Original automatic behind 305

Postby cammerjeff » Mon Sep 21, 2015 1:04 pm

I don't know about V-8's, But every Automatic behind a 231 Buick from 78 to 80 I have ever seen were T-350's. But I have seen M200's behind Iron dukes of the same years
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Re: Original automatic behind 305

Postby stage169 » Mon Sep 21, 2015 3:12 pm

It is possible that GM decided not to continue the TH200 for the V8 H body after 77. You can find the lawsuit against GM on the longevity issues for the TH200 easy enough on the net. The crazy thing is that GM continued to put it behind V8's in other models including trucks. The RPO MX1 basically means a three speed automatic (TH200, TH350 and even the TH400).

Having said that if you look at transmission parts on GM wiki parts everything I've seen stops the use of the TH200 behind the V8 after 77. So it wouldn't surprise me that this is the case.

Wish I had proof for the answer but I don't. Something I've looked into in the past just out of curiosity. Maybe the PDM info for 78/79 would show the trans options? I think Marco has one?

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Re: Original automatic behind 305

Postby marco_1978_spyder » Tue Sep 22, 2015 12:13 pm

Of the 2... I think the 200 is geared better (I could be wrong on that one) Steeper 1st gear for use behind low torque 4cyl engines. Less clutches and lighter over all assembly requiring less hp to turn = the 200 metric might the faster 0-60 of the 2 tranny's considering a stock 77 305 vs a stock 78 305... but wouldn't take much abuse or extra power.

Who has a stock one anymore anyways. There's a few but not many.
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Re: Original automatic behind 305

Postby spencerforhire » Tue Sep 22, 2015 4:32 pm

I find it funny that GM gave up on the TH-200; this particular transmission may be weak in it's stock form, but they are highly popular in NHRA/IHRA Stock Eliminator. Beefed up race specs, they are apparently lighter than a TH-350 and the lower gear ratios make them harder launching.
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Re: Original automatic behind 305

Postby stage169 » Tue Sep 22, 2015 9:54 pm

Ken, there are a lot of TH350 examples for the 78 & 79 v8's, here is a 79 build sheet from AusRs you can just make out M38 at the top of the third column.
Image

Ken's 78
Image

The RPO for a 3spd auto trans in 78 & 79 is listed as MX1 for the Monza. Here is an example of a LG3 5.0 V8 with MX1 and M29 (TH200). Although a 78 four door Malibu if Chevy did it with that it wouldn't be a stretch to see it in a Monza. MX1 was a catch all for 3spd auto trans and if your memory serves you correctly that has got to be the case for the 78/79 Monza's.

The views and opinions expressed on this post are soley those of stage169. These views and opinions do not necessarily represent those of any/all contributors to this site. :D Brian
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Re: Original automatic behind 305

Postby PeerStalkHawk » Wed Sep 23, 2015 2:54 pm

I had mentioned this before in a thread but the th200 metric was used in later h-body years too such as in the '1980 2.5 Monza I had and other cars into '87. But by then it had some changes such as the low/reverse clutch drum and plantetary gears shared with the later 200-4r and also they had a lock up torque converter. Known as the th200c. The shift detent cable on the '80 would look identical to the th350(the teardrop shape) rather than the earlier long slotted-type such as on my v6 1977 Skyhawk with the earlier th200metric. Only this is the detent cable setting is very important to the shifting and long life of that transmission(including the teardrop style on a th200). I can say the th200 on that '80 Monza ran excellent with absolutely no mods whatsoever. I do know that it was very much recommended to put a shift improver kit on the th200 right from new to correct some shifting and clunking issues which it did and to prolong the life of that trans.. I read that that should really have been one of the first of any mods to do on a new one. Now, my '77 Skyhawk's th200 mteric the (motor in this car was set up for stock eliminator-type racing) was gone through and modified a bit with things such as the better clutches and also has the TransGo shift improver kit in it, is still going perfectly fine after a lot of years later and I can tell you the hp/torque is very much more than stock. It also has a 3600+rpm stall converter and much lower rear gears with small diameter tires and is street driven here and there but of course likes it a little faster such as on the highway and at acceleration/steady higher speeds. I run Amsoil Super Shift Racing atf synthetic fluid and have the detent set up carefully for the firmest best shifts and it works great so far and the fluid is perfect. So I don't think a properly set up stock th200 should be a problem at all on a more stock 305 if it is in good shape to begin with. And yes, things such as the lower 2.74 first gear, less resistance in rotating mass, and bit case lighter case does help give a slight advantage if looking for a slight edge in et/performance. Although, some th350's can be built to have the lower gearing internals and better non-drag internals to basically match. I hope some this helps.
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