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View Full Version : Any tranny gurus out there?


godtool
02-16-2007, 06:22 AM
I changed the vacuum pod on the back of my TH350 auto transmission and TV cable for the kick down. My transmission seems to be shifting from first to second good and also from second to third when I let off the gas. I guess with 35 inch tires and 373 gears I will have to get going pretty fast to get that third gear change. I just can't get going fast enough on the roads around where I live. The tranny seems to stay in second until I let off on the gas before it will change into third. Even though I change those two parts, I guess there could be some internal wear that causes it not to shift well from second to third, or I just need to get out on the freeway. I do remember when I was going fast on the highway I used to switch back into second out of drive and then back into drive to get my third gear shift. I believe before that it would switch to third until I got over 90-100 kms. does that make sense to anyone?

kootenaycat
02-16-2007, 10:44 PM
Still sounds like it's sensing too much throttle pressure (modulator?)overcoming governor pressure. Or something like that, not an auto trans guy, been too long since school! :D Need to review my apprenticeship books.

The TH350 is the most basic of transmissions, and if the fluid smells clean, not burnt, it's not noisy, and doesn't flare between shifts, it's more then likely NOT hard parts.

Under moderate throttle on a flat road, what speed will it shift to 2nd? My TH350 with stock 3.08's and 31's will shift to 2nd at around 10-15mph under light to moderate throttle and then into 3rd by 20-25mph if I'm really easy on the gas. If I give it half throttle at that speed it will downshift. So with 3.73 and 35's it is like 31's and 3.30's, very close to what I have, so it should be upshifting much earlier.

Hope someone else with auto trans experience pipes up, but I'm thinking governor valve sticky? I think it's only accessible through the tailsection of the trans, been way too long since I had one apart.

weiser
02-16-2007, 11:14 PM
I don't Know if this will help any but you running 373s and going to a 35inch tire. This is what I have to do.
44356
I have ta change my gears from 355s to 456 Just to bring it close to factory settings. Untill i get er done, first gear is dang hard on the clutch.
Oh ya when my speedo says 80 my gps says 102.:eek:

brothergrimms
02-17-2007, 01:25 AM
check your vacum line from motor pod make sure it not the line but none that is the problem get a small scerw driverb flat head put it in the pod trun cratuor clock wise 2to3 full truns should help ajust to your likin.

godtool
02-17-2007, 10:06 AM
vacuum line has good vacuum but I'll double check entire line. I'll adjust the pod. I need to find a book on rebuilding a th350 - check library? Time to learn some new stuff:confused0006: . I'll let you know how it works. I have 410's in 3/4 ton diffs to go in this summer or when I want to get going on it. Got diffs with free truck:) .

kootenaycat
02-17-2007, 12:55 PM
Oh ya when my speedo says 80 my gps says 102.:eek:

Not sure about your year of Ford, but the '92 to '96's speedos were easily relcalibrated by grounding out a terminal under the glovebox and entering a new calibration number by pressing the trip/reset button on the cluster. Haven't had to do any '97 and newers though. Worth checking out.

sj-x 500
02-17-2007, 02:02 PM
whoa whoa whoa... you say that again kootney? i got a 95 f-150 that is on 35's and the speedo is all out to fuck, what is the calibration number needed for such a change?

weiser
02-17-2007, 10:20 PM
Not sure about your year of Ford, but the '92 to '96's speedos were easily relcalibrated by grounding out a terminal under the glovebox and entering a new calibration number by pressing the trip/reset button on the cluster. Haven't had to do any '97 and newers though. Worth checking out.
[36] Thanks I'll be looking into that.[cheers]

kootenaycat
02-17-2007, 11:39 PM
whoa whoa whoa... you say that again kootney? i got a 95 f-150 that is on 35's and the speedo is all out to fuck, what is the calibration number needed for such a change?

Get me your gear ratio and I'll send you the instructions how to recalibrate it. Really simple. Will get them off Mitchell at work Monday.

Only catch is it can only be done 6 times (I believe) max, then you need a new speedo head. SO, as long as yours hasn't been recalibrated more then 5 times, your good to go! There is a way to see how many times it's been done, can't remember, will find out. I think it's push the odo reset button and hold while turning the key on. Some numbers will show up, then push the reset button again to see another number(s). Don't worry this won't change the calibration. You have to ground the connector under the glove box to do it. The odo should have some numbers on it, single digit for number of times, and then calibration number. Been a while since I worked for a Ford dealer!

kootenaycat
02-19-2007, 09:28 PM
Here is the programming procedure for the '92-'96 F150's. Forgot to check if the '97and newer are the same.

Mitchell won't let me "copy/paste", some kind of copyright protection, so I just did a printscreen and saved as a jpeg. Some of the steps were cut off, and repeat themselves on the next picture. CAREFUL in step 7, the 6th step down, ONLY PRESS THE RESET BUTTON ONCE! Where the one page cut off, it looks like you have to press the reset in two seperate steps then press select button to change the conversion constant, it is just a copy! If you press the reset button twice in step 7, you will knock off one of the chances to recalibrate the speedo and you only have 6 tries! After you have grounded the wire under the glovebox (I think that's where it is!) and entered the programming procedure, you can still cancel by turning off the key, you won't have ruined one of the recalibrate chances.

I'll try to crop out the text so it's not as confusing! :dontknow: :D It's really pretty simple.

sj-x 500
02-19-2007, 10:35 PM
k, cool, but what is the constant for a 35x15/r15...

kootenaycat
02-20-2007, 12:07 AM
Ooops, forgot to put up the SCC formula! [16]

Speedo Conversion Constant = (Tire Revolutions per Mile ) X (Speed Sensor Teeth ) divided by 8000.

So first your tire RPM is = 1528 - (28 X Tire Diameter), so 1528 - (28 X 35) = 548.

I'm assuming you have an 8.8 rear end that has 108 teeth ring.

Next SCC = 548 (tire RPM) X 108 (sensor ring teeth on rear axle) / 8000. SCC=7.398, rounded off to 7.40 or 740 (entered in the instrument cluster) without the decimal as the instructions say.

Clear as mud, right! I want to double check something at work tomorrow. Went through calculating a 31" tire with the 8.8 and came up with a different constant then is in the chart. I got 8.91 and the chart is 9.18 :confused: For some reason, I think I remember a typo in the Ford manual.


Have you checked what constant is in the truck right now? Step 4. Let me know.

godtool
02-23-2007, 12:43 PM
Thanks everyone.[cheers] I see a lot of technical stuff has been added.[36] Cool. I replaced my TV cable and my vacuum modulator. My truck down-shifts good again. Replacing the vacuum modulator on the back of the transmission solved my upshift problem, but with a 35 inch tires the upshift from second to third is considerably higher than normal. I've yet to try backing out that screw more on the pod. I don't think I'll worry about it. I'll bring a screwdriver with me in case it bothers me in the future. I don't have 456 gears but I do have 410's diffs. I'll put those under in the summer.[36]