C6 tranny not wanting to shift correctly

[IHI]

i have a 89 E350 cube van with the 7.3IDI and C6 trans 180Kmiles. It's worked flawlessly for years, then yearly this year it acted like the vacuum modulator went bad. 1st gear would hold until truck was going appro 25mph and then clunk into 2nd, will not shift to 3rd gear until truck reaches 46mph. before it'd run through the gears quickly. As it sits, trying to drive it in town is terrible since it just wont go into high gear due to speed limit, so i'm stuck rolling in second gear revving the engine like mad to do the typical 25-35mph in residential neighborhoods.



I replaced the vacuum modulator, checked the vacuum line from the modulator to the steel hardline at both tranny side and top of engine, no apperance of cracked vac lines causing vacuum leak. It did this earlier this year for about a month, then stopped and was good all summer until about a month ago and now problem is back.



Any ideas as to what to look for next?



Thanks

Josh

[FULLAUTO]

this is just a guess but check vacuum pump belt could be loose bolts on pump cold be loose , pump could be bad , line to pump could be bad,vacuum pump creates vacuum that allows tranny to shift and brake booster to work they can go slowly or all at once
wade

[Mr_Roboto]

I would post this up in the 6.9 forum since it is not van specific.

There is a "doo dad" on the side of the IP that creates the vacuum signal for the modulator.

This unit can be tested, I've never dealt with them but other folks can help you with that procedure.

[IHI]

Took it to a shop today as my work load for construction and preparing for the upcoming "snow/freezing rain" called for this weekend has me busy. Ended up just being a few vacuum lines coming off the injection pump, leaking diesel fuel due to bad lines (which i had fixed this summer) had loosened the hoses up a bit enough that they swelled and vibrated off the nipples and created huge vacuum leaks. They got'er fixed and all is well again

Thanks for the help

Josh

[cdnsarguy]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">There is a "doo dad" on the side of the IP </div></div>

That is the Vacuum Regulator Valve (VRV) it is adjustable to get correct vacuum to the trans..... A "vacuum pump test" is on my gallery if you want to check the Vpump anytime.