trans slipping

TH400, 125K on it, behind a 454. Never had a problem shifting/slipping at all until this week. Now after towing a trailer into the mountains it's slipping. Probably the obvious answer that I fried it. Didn't
really go up any huge hills and it was only an hour and 15 min trip.
Symptoms now are slippage pretty bad in 1st and 2nd. Put it to the floor engine sounds fine but not picking up speed anywhere near as fast as I should. Seems to shift kinda hard also.
So my questions:
First, is there anything simple I can check? I checked the fluid already and it didn't smell burnt and was at the right level. Should I get a gauge and check the line pressure? If so what kind of gauge(what size end) will thread to the port on the tranny? Do I also need a vacuum gauge to check the modulator? If so what should it read? Is it worth dropping the pan and changing the filter? It had a tranny service about 2k ago with a filter change. No metal shavings in the pan then.
If I'm just totally screwed here, any recommendations on replacement? Suck it up and go to the dealer? Will they warranty it if I put it in(yes I've replaced engines/trannies before and have the equipment to do it). Am I better off finding a good shop and just having them rebuild it? If so anyone know any good shops in the albany ny area?
Thanks in advance, Ed
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125K behind a 454, aint got no room to complain there at all , especially if she's done a lot of towing. Kind of hard to beat Target tranny if its available for the price vs. the warranty. As long as you do everything they say to do when you change it then the warranty will be good even if you put it in. I have found it cheaper to have Chevy replace 700r4's than to have one rebuilt in the past, and get a better warranty to boot. 3yr 36,000 mile. Believe the warranty is the same on the TH400.
Whitelightning
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On Wed, 07 Jun 2006 02:18:10 GMT, "Whitelightning"

Sounds like you did not have aux tranny cooler because THM400 are pretty tuff if kept cool. I have a 79 J20 with origanl THM400 in it and it started life as a farm truck and them plowed snow for many years and tranny still works like new today but it did have regualr fluid changes and a small aux tranny coole added to it too when it was new. One more tip, when you tow with automatic and you are pull hills, keep rpm above 2500 RPM on hard pulls as that way you will be fully off the stall of converter and the extra heat it makes while on it. ----------------- The SnoMan www.thesnoman.com
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SnoMan wrote:

I'm not sure I understand the problem here.You say it doesn't pick up speed like it should.Do you mean the engine revs go way up out of proportion to truck speed or just that the accelleration is not good. Reason I ask is that a trans that is slipping badly and has been under load will have burned smelling fluid 99% of time. And the slippage is usually most pronounced DURING shifts,yet you say it shifts HARD! Why not take it into a shop that has a free check,(AAMCO usued to have this)- just don't let them drop the pan. So when does it slip,when you are IN 1st or second and punch it? Could be the TC?
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Brian,
Yes engine revs go way out of control, to the point of if i put it to the floor at say 20 miles per hour it literally takes about 15 seconds to get to 30 mph. Good idea on the free check, I'll look into it.
brianorion wrote:

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If it was the TC, if you not have much power at low speeds (no torque multiplcaton) and tranny would always feel loose and would do the same in all gears including reverse. ----------------- The SnoMan www.thesnoman.com
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