transmission & rear end gears

[jaypcee]

I changed the transmission in my E350. It is shifting into all the gears but it only goes about 60 mph. Is it possible that my rear end has different gears in it than normal and that is causing the van to go slower. How do I find out.

[dxrflyboy]

There should be a tag bolted to the back cover with the axle ratio stamped into it.

[ModMech]

He posted that about 6 months ago, he installed a C-6 in his van as I recall. The solution was that the vacuum line is either broken/leaking or the modulator is bad (or the cap was left on, seen that a few times) so it's not upshifting into 3rd (trans thinks you are at WOT all the time).

He never checked any of that, was convinced that the rear end could cause the problem. All C-6s are 1:1 in third and 1.46:1 in 2nd, so that CANNOT be it.