Your Chevy C3500 Dually pu 5sp manual transmission doesnt shift into each gear smoothly and sometimes not at all. If you top off the reservoir of fluid under hood it gets better but still righ?

If topping off the transmission fluid temporarily improves shifting in your Chevy C3500 dually, it strongly suggests a leak in your transmission system. The fact that it still shifts roughly even after topping it off points to either a significant leak or an internal transmission problem. Here's why and what you should do:

* Leak: A leak, somewhere in the transmission case, lines, or seals, is the most likely culprit. The fluid is escaping, lowering the level and causing poor shifting due to insufficient lubrication and pressure. Topping it off simply buys you temporary time before the level drops again. You *must* find and fix the leak.

* Internal Transmission Problems: Even with sufficient fluid, if the transmission itself is worn (worn synchronizers, damaged gears, low clutch pressure), shifting will be difficult. The leak could be exacerbating an already existing problem.

* Clutch Issues (Manual Transmission): If you have a manual transmission, clutch problems (worn clutch disc, pressure plate, throw-out bearing) could contribute to difficult shifting. However, low transmission fluid wouldn't directly cause this. It may still be related to the leak if the clutch system is somehow compromised.

What you should do:

1. Don't keep driving it like this: Continuing to drive with low transmission fluid will cause severe damage to the transmission, potentially leading to a very expensive repair or replacement.

2. Find the leak: Carefully inspect the transmission and surrounding areas for any signs of fluid leaks. Pay close attention to the transmission pan, the bellhousing (where the transmission meets the engine), and the transmission lines.

3. Check the fluid level properly: Don't just top it off. Find the correct way to check your transmission fluid level (your owner's manual will explain how, usually requiring the engine to be running and at operating temperature). If it's low again quickly, you have a leak.

4. Get it professionally diagnosed: Take your truck to a qualified mechanic specializing in transmissions, especially for heavy-duty trucks like your C3500. They can pinpoint the exact cause of the problem (leak, internal damage, clutch issues), provide an accurate repair estimate, and perform the necessary repairs. Ignoring the problem will likely lead to a much more costly repair down the road.

Ignoring this issue could lead to catastrophic transmission failure, leaving you with a very expensive repair bill. Addressing it promptly is crucial.