got a 71 lark that came with a buick 350, th350, and 2.56 gears in the rear. i have changed the engine to a 455 alum headed monster and keep the tranny and rear as a temporary solution to allow me to run at the track. this is my problem i. when i put the tranny in 1st manualy the car will not move hardly, it feels like the thing is in park. i also verified this as not being a linkage adj problem by going through and adjusting the linkage just to make sure. the trans manual shifts into all park, drive, 2, 1. when i take off normal i can't feel a shift until wot. so is 1st out and when i go wot i get 3rd? i'm not that savvy on transmissions does a th350 have 2 or 3 gears? all i know is i need some help anybody?
You know sometimes the board is slow and you might not get an answer for awhile. The first thing you do when the trans acts funny is to check the fluid and level. Is it red or does it look and smell burnt. If it looks like mettallic red paint, the trans is toast. Fluid OK? check the vacuum supply to the modulator. Any leaks, or restrictions/bends in the line? Check the modulator, does it hold vacuum? Any ATF on the vacuum side? Beyond that, it gets technical, and if you've never worked on transmissions, you're better off having a shop look at it. I can tell you this, Heavy Car + Big Torque + Perfect traction = broken trans if the trans aint up to the engine power. A TH350 can be built to take the abuse. A TH400 will take the abuse also in pretty stock condition. Did it just start doing this?
Do you have the throttle cable connected? As Larry said, the vacuum modulator must be getting appropriate vacuum also. Lot's of things come to mind but the one that stands out due to the symptoms is that vacuum modulator. If it isn't connected at all, the trans will act all sorts of crazy.
Somewhat odd symptoms. It's hard to determine sometimes what is going on over the internet. May be a hurt low roller clutch, so it has no low gear and doesn't really engage until you are in 2nd..
to be honest i think it has always done this the fluid is correct and the vacuum and cable are hooked up. the thing that really gets me is that i can't put it into 1st manually. lol along with the thing not shifting . i told my dad about it and he laughed and said if the car is running 14.4 with no 1st and traction just wait till i get this stuff fixed. how important is 1st gear anyway. my dad said he had a van and first went out and it was a dog to start off. i told him that the engine is so powerful its hard to say because it aint a dog of the line. powerful engines are great but in this case i may have a seriously hurt tranny and can't even tell it
Like Larry said (well, he was nicer about it) you killed your TH350. You can get it rebuilt to handle enough torque or you can find a TH400 and a short tail shaft and put it in. For my money, I think I would have your TH350 rebuilt to withstand 600 ft.lbs of torque or more. The cost for each will be comparable, but the 400 is a lot more work...
i rebuilt my 400 and it wasnt that bad oNo: since you have the 350 and obviously the driveshaft works with it, i would have it rebuilt for the abuse. It has a lighter rotating mass, means quicker acceleration basically.
I would first see if you do in fact have a TH350, or if it's maybe a ST300. Maybe you only have a 2 speed... If you have a TH350 I have a post that covers rebuild and modifications here: http://www.nastyz28.com/forum/showthread.php?t=53671 I also have some specialty parts that are specific to getting the TH350 tgo handle 500+ lb/ft of torque. The 36 element sprag/drum setups are the major piece I recommend at that level. They make the TH350 a much stronger setup. Compare to the stock parts:
put in a new vacuam modulator valve and the exact same results as listed above. i think i going to confirm this thing starts off in 2nd gear. i took it to the track today and got the same time but picked up 1 mph went from 98 last week to 99. now i'm on the hunt for a tranny builder and a posi rear end. anybody got a rear they don't need?
on second try, since the board doesnt like .bmp images :grin: Im not so familiar with th350's myself, but i would guess the governor is housed here :TU:
ok i'm dumb founded it put on a vacumm mod valve and got nothing but after about 30 miles of driving the thing now want to shift from 1 to 2 sometimes. i don't like a sometimey tranny. is this thing just getting back right or is this thing just toast. haven't had time to look at the governor but what am i looking for or measuring. do i just look for obvious damage and brake clean it off then stick it back in? or is there something i suppose to adust?
There is no way we can diagnose your trans over the internet. All we can do is make suggestions of things you can check. When you pull the governor out, look for obvious signs of damage to the drive gear, the lands, and governor bore(in the case) Make sure the weights move freely. If it is gummed up, yeah, hit it with some brake clean and lube it back up with ATF before installing it. Hold the governor upside down by the drive gear. Pinch the weights together and let them go, and observe the valve for movement. If it doesn't move it may be gummed up. If you have some feeler gauges, you can measure the clearance between the valve and the intake port (close to the gear) and the exhaust port (closer to the weights) Should be .020. Pinch the weights together, measure between the valve and exhaust port. Let the weights hang free and measure between the valve and intake port. That's all I have. If it still won't behave, have a shop look at it. BTW, you do have the detent cable hooked up and adjusted, right?
