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1968 delta 88 I believe has the T400 . It’s a 3 speed auto .
My question is does anybody have a video or pictures on how to adjust the shift timing on these transmissions ? The car shifts very fast from 1st,2nd,3rd under normal acceleration. Also, if you put it to the floor in first gear it winds out way to far and doesn’t want to shift unless you lift your foot off the gas a tad, then it immediately shifts to second . All shifts are smooth and it does down shift from 3rd to 2nd and 1st as it should. Thanks .
Could be a TH350 or a T 400. Is the pan almost square with one corner cut-off? If yes it is a TH350.
Is there a switch inside the car at the top of the accelerator pedal? If yes it is a TH400.
Re: the shifting start with confirming the correct fluid level and that the rubber connectors/vacuum hoses at each end of the steel modulator line are good shape. Look for rust along that same line that could be a vacuum leak.
It’s a 455 . If that’s normal how do I correct it not wanting to shift from 1st to 2nd wide open throttle ? I don’t have a tack but just by sound I have defiantly wound it up to at least 5000 and it won’t shift unless I lift the throttle for a split second to let it shift then stomp it again
Could be a TH350 or a T 400. Is the pan almost square with one corner cut-off? If yes it is a TH350.
Is there a switch inside the car at the top of the accelerator pedal? If yes it is a TH400.
The TH350 didn't exist in 1968. The switch pitch converter was dropped starting with the 1968 model year. The switch on the accelerator is the kickdown switch. If the car is a 350-powered car, the trans will be a TH375, which is a light-duty TH400. This is easily identified by the tailhousing, which will have "375THM" cast into it. All other full size cars got the TH400.
Assuming the car is secure on car stands, how would it run you over? Block the wheels on the ground, set car stands under the rear axle and relax.
As long as the stands are in good shape, and have a weight rating that exceeds the vehicle weight, and properly located and on solid ground the car isn’t going anywhere.
I had the car up on a lift and I think I can get the cover off but not sure if there’s enough clearance to actually slide the governor out with the exhaust . I was doing some other things while it was on the lift so I didn’t try . Gunna take another look soon though and give it a shot . Will update then.
I had the car up on a lift and I think I can get the cover off but not sure if there’s enough clearance to actually slide the governor out with the exhaust . I was doing some other things while it was on the lift so I didn’t try . Gunna take another look soon though and give it a shot . Will update then.
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Last edited by ClaraBerkey; Apr 21, 2023 at 10:11 AM.
-Have you performed any recent services on the car?
-Did this shifting problem just start?
-How many miles on this trans?
-Has the fluid & filter ever been serviced?
-Is the cars state of tune good? Good vacuum signal...properly adjusted timing and carb?
-Since it's downshifting OK I'd look at the modulator before the governor.
Assuming this is a TH400 it sounds like dual root causes(problems)...Cause 1...Your description describes classic modulator trouble. Short shifts = modulator isn't functioning as designed. Not a sufficient vacuum signal to overcome the internal spring & bellows = short shifts as it's not sensing enough vacuum and thinks the car is moving faster than it actually is.
-Verify the line to the modulator is hooked up to a straight intake manifold vacuum source. Not connected to the carb.
-Verify the line from the source to the modulator valve isn't restricted, cracked, or leaking. I've witnessed a plugged steel modulator line cause high and WOT 1-2 upshifts.
-Verify the modulator is good. Does it hold vacuum?? If it's bad install an adjustable Standard (Brand) TM-50. You can now adjust your upshifts. Follow TM-50 initial installation & final adjustment procedures. You will lose trans fluid. Be ready to jamb the new valve in quickly. Helps if the car is safely raised on the passenger side.
Symptom 2: or root cause 2,
1-2 upshifts occurring only at full throttle could be the detent switch sticking or the solenoid sticking open or bypassing fluid. Look at the switch above the gas pedal. Verify smooth function(slides freely w/full travel). Verify it with an OHM meter. Loss of the detent signal causes no automatic downshifts. Stuck on causes WOT upshifts.
Symptom 3: (which you do not have but I'm using as an example of a defective governor signal)...
1st gear only no 1-2 upshift could be a sticking governor, a bad governor-driven gear, or a bad 1-2 shift control valve... Deeper problems will need deeper troubleshooting meaning it's time to seek out a good trans shop that knows analog transmissions.
