TH400 shift speeds? And i have this momentary wobble that goes away...

[Dabba]

Firstly: I had my mechanic replace the modulator on the tranny and check for vacuum leaks, says he replaced it and theres no leaks. The tranny shifts at around 21mph and then at about 36mph. My only other experience is with 2 k5s with a 700r4 and the diesel seems to be pretty loud before it shifts and it seems to still shift pretty hard most of the time. Is it normal in these trucks? I know deisels dont really have a high redline and i dont wanna think im overreving to shift?

2nd thing: I noticed when driving down the road, if i hit a big bump or pothole, the truck will start this nasty wobble, as i slow down the wobble starts to go away than disspears completly, and as i speed up its normal again. This happend twice so far, so by slowing down i seem to get things back into the right order and it drives fine again. Feels like its coming from the front end. Any ideas?

 

[crusty]

My truck had a high shift problem that was due to the old, deteriorated vacuum hoses collapsing under load. A couple of bucks worth of new hose and it's fine now. I replaced all the rubber vacuum hoses from the pump to the regulator on the IP and down to the modulator. They looked ok but were softened from age.

 

[Westech]

mine shifts at 20 and 30 MPH. You can adjust the modulator but best thing to do is install a Heavy Duty Shift kit to increase the line pressure and put in the softer springs in the governor to lower the Shift point speeds.

 

[CUCVFAN]

Those aren't crazy shift points, but you can rotate the top of the vacuum valve on the passenger side of the IP toward the rear of the truck to lower the shift points. Higher shift point means more line pressure and firmer shifts which usually equals longer tranny life (not that you will drive enough miles to wear out the TH400).

 

[CUCVFAN]

As for the wobble, check the tranny mount, tire balancing and front end parts (king-pins, tie-rod ends, etc).

 

[Dabba]

i told the guy whos doing the inpection to check the front end, so well see. higher shift points are better for tranny life? fine with me then heh, sounds like mine are okay then, i was actually concerned more with 1st to 2nd but if its not that off than good. Thanks for the help, ive spend so much so far already on prevenative maintainence i cant get tires for awhile OH well, im stuck with bald highway tiresss

 

[Goatwerks]

Check the vac pump, low vac will cause hard late shifting and eventually break parts. TH400 should shift firm but not slam. As for the wobble, classic worn ball stud symptoms(aka king pins).

 

[BIG_RED]

I've got same shift problems. Vacuum lines were what I had in mind too.. mine are just rotting away. I'll let you know if new ones helped me any. I heard that where the vac line goes into the tranny, that there's some kind of adjusting screw.. like in the hole you hook up the line to. A buddy of mine told me this, he only has experience on civilian TH trannys, but I'd imagine they're not much (if any) different from the Mil ones. I haven't had a chance to take a good look at mine, but I'm thinking my vacuum line is pretty small diameter tube, must be one tiny screw if its down a nipple hole. Anyways, just my thoughts.. I'll keep you posted on if I have any luck. I'd like to know if anyone knows about the adjusting screw, I don't know much about how an auto tranny can be toyed with. Thanks.

 

[tm america]

check vacume at the modulator with a guage it should be at least 20 at idle and drop when the throttle is pressed.you can use a small screwdriver to adjust the modulator turn the screw out or counter clockwise to lower shift points you can take it all the way out if you need to .also check to make sure there is only one o ring on the modulator ive seen guy forget to remove the old one.does it have kick down and does it shift earlier when you drive it easier

 

[tm america]

shift kits raise the shift points not lower them they raise line pressure to about 180 with a manual valve body or a trans brake if you put one of those springs in the pressure regulator you will have to add some weight to the gov to get it to shift anywhere near right since it will take more gov pressure to over come the shift valves with more line pressure more weight onb the gov makes it shift earlier since the weight will sling out faster . so to maove shift point with the gov you need stiffer springs or heavier weights but .its ussually a gov sticking or a lack of vacume

 

[tm america]

i rebuild trans for a living if you guys have any questiions you can pm me if you want .we do alot of racing stuff where i work so i have alot of experince with fine tuning them

 

[Cucvnut]

Sounds like DeathWobble could be a bad dampener shock or the king pins on the dana 60

 

[b4thundr]

i just fixed my wobble its the damper shock mine was wore out!!! replace that and I'll bet it goes away!!!

 

[Crash_AF]

A steering damper just masks other problems... check all of the wearables in the front end first. Kingpin wear is the most common problem for the 60, but there's also the possibility of tie rod wear and a slightly lesser possibility of loose wheel bearings.

On the shifting issue, those sound ok to me. My 1009 shifts at 20 and 30,with your lower gearing, you're revving a little more, but I'd say those are right. If you want to test it, put a hand vacuum pump on it and a gauge on the outlet, pull about 20" of vacuum on the gauge and then open the throttle, the gauge should drop to 8" at WOT.

Later,
Joe

 

[b4thundr]

yeah but 25000 miles? do you think that there is alot of wear?