CUCV speedometer does't work and tranny shift problems.

[gjones]

The speedometer doesn't work and the tranny seems to only shift to 2nd gear. I'm thinking "Vehicle Speed Sensor". And if so, where is it? Any idea's guys?

 

[Mg84648]

Your speedometer problem is separate from your shifting issue and have nothing to do with each other.
For the shift issue check your vacuum lines from your vacuum pump, to your regulator on your injection pump, and from there down to the modulator on the right side of your tranny. Pay particular attention to the rubber adapter piece on the regulator that looks like an "F". It dries out and cracks. You can just omit it and hook you lines straight to the regulator.
Your speedometer gear may be stripped at the adapter on the tranny or maybe just needs to be lubed.
Hope that helps.

 

[dependable]

I'm thinking "Vehicle Speed Sensor".

No Speed sensors on CUCVs, or related modern electronics, that is what many of us like about them.

Mg's suggestion to check vacuum though to modulator is a good one on the shifting.

The speedo heads have been known to fail, and are fairly easy to replace. First check that speedo cable is fully engaged with back of insturment cluster.

 

[MarcusOReallyus]

For the shift issue check your vacuum lines from your vacuum pump, to your regulator on your injection pump, and from there down to the modulator on the right side of your tranny.

Mg's suggestion to check vacuum though to modulator is a good one on the shifting.

Those vacuum lines are so easy and cheap to replace, and so often the source of shifting problems, it just makes sense to replace them all in one shot.

 

[mike634]

Anyone know what size vacuum line to use??

 

[cucvrus]

3/16" at the front and 3/8" off the pump. You can get nylon elbows and adapters at any hardware store. Top to transmission and bottom to vacuum pump. I hope that helps.

 

[gjones]

The cable was broken at the transfer case. Just got the new one in. And the tranny was over 4qts low. Replaced the 1.5" of vac line at the modulator. From there its metal up to the engine. Don't see a vacuum pump. Only thing I see running off the 2 belts are the 2 alternators and the power steering pump.

 

[tim292stro]

Vacuum pump is tucked under the air cleaner housing on the back of the engine (where the distributor would be on a sparky/gasser).

Looks like this:

 

[goldneagle]

I would do a service on the tranny. Drop the pan and install a new filter and then new fluid. Check for leaks.

 

[joshuak]

The cable was broken at the transfer case. Just got the new one in. And the tranny was over 4qts low. Replaced the 1.5" of vac line at the modulator. From there its metal up to the engine. Don't see a vacuum pump. Only thing I see running off the 2 belts are the 2 alternators and the power steering pump.

Should have 3 right? Redundancy for brake system and steering.

 

[Matthew Gravley]

My speedometer cable just needed a little lube and was good as new. Tranny fluid, filter and pan gasket is only a few bucks. The beauty of our early GMs.

 

[gjones]

Thanks guys. And Merry Christmas.

 

[gjones]

The new cable was the answer. The speedometer now works. Shifts to all 3 gears, but whines up quite a bit before it shifts to 2nd and 3rd. Going to service the tranny and check the vac. line at the vac. pump next.

 

[rustystud]

The new cable was the answer. The speedometer now works. Shifts to all 3 gears, but whines up quite a bit before it shifts to 2nd and 3rd. Going to service the tranny and check the vac. line at the vac. pump next.

The vacuum modulator is probably going bad. They can be adjusted by removing the vacuum hose and inserting a small straight screwdriver and turning the adjusting screw in or out.
To adjust for a high shift point turn the screw out. This should bring the shift point down where it should be.

 

[mike634]

Thanks CUCVRUS. That's the info I needed.