SBurkle

Grip Shift with Shimano drive train continually goes down the gears until its is on the bottom cog on both the front and rear derailleurs. Is this something I can adjust or do I need to purchase new shifters. If needed I can attach pictures and more specific specs but I want to see if this is and easy fix first. Thanks

dedhed

With any indexed shifter the first course of action is to give it a flush with WD40. Spray it into any place you can while working the shifter back & forth. Better if there are any covers you can take off.

fietsbob

Sram's most basic grip shifters for OEM assembly, * have been made at lowest cost,

I have even had to throw them away because the cable replacement was never considered..

* including those for shifting Shimano's derailleurs..

you can adjust the cable tension at the end its attached to the derailleurs.. with the clamping bolt.

I suggest you replace them with friction thumb shifters those are under $20 for the pair including cables..








..

Bill Kapaun

I assume you mean the smallest cog/ring in physical size.
That's what you'd expect from a friction shifter that doesn't have enough friction to hold the position.
Sure the shifters are Shimano, or is this an X-mart bike with a Shimano RDER and unknown shifters?
I have seen these bikes that have a "Shimano equipped" sticker and the only Shimano part is their RDER made for such bikes that is so cheap, it isn't available through normal channels. I mean BELOW Tourney level.

canklecat

If it's a Shimano RevoShift grip shifter, it isn't really serviceable. It's cheap but functional plastic and a few bits of stamped metal and springs, snapped together. When it breaks or wears out all you can do is replace it. Fortunately they don't cost much. I bought backup RevoShift kits for around $10, which includes both grip shifters and the basic cables and housings to fit most hybrid bikes. They'll usually last at least a few years. Eventually the plastic bits will wear or break. It's designed for comfort hybrids and entry level mountain bike-lite bikes that will be ridden a few times a year and mostly stored in the garage.

I've seen some YouTube videos demonstrating disassembling and attempting to fix RevoShift, but it really isn't worth the effort. Unless folks are just curious. Been there, done that, wasted hours on the chore just to prove it would have been more time and cost effective to just buy a new set. Which I did, after satisfying my morbid curiosity by doing on autopsy on the broken RevoShift.

If you don't mind friction shifting rather than indexed shifting, for about the same price you can buy the SunRace SLM-10 thumb shifter levers. Also cheap and functional but mostly metal and will last a long time. They work surprisingly well for being so cheap.

Andrew R Stewart 

So the OP said "Grip Shift with Shimano" to me this means Grip Shift (likely MRX) shifters and Shimano ders. Many of the replies don't reflect this statement.

The Grip Shift units have a small spring/clip inside that is what rides up and down the ratchet "rack" both producing the audio clicks and the holding power in a specific gear. When the two halves of a Grip Shift come apart (due to stationary grip movement then the rotating grip being able to also move sideways) and that metal clip gets dislodged or lost so to does the gear position holding ability. This is the most common reason to end up with what the OP states. The next common reason is that the grip Shift neck (where the cable is routed within as it travels to the casing) has broken. The last common failure is the Grip Shift "bofy" has cracked and thus the metal clip no longer has pressure on it to engage the rack. The cracks and broken plastic possibilities should be very easily seen from the outside. The missing clip is "found" when the two halves are separated. Since the replacement (if actually available currently) are only about $15 I wouldn't spend too much time trouble shooting. Andy

Retro Grouch 

"Shimano derailleurs and MRX Grip Shifters is a common low end spec. If you ever have to replace the shift cable, you have to disassemble the Grip Shifter. When you do this, be prepared to catch the horse shoe spring Wien it falls out AND be sure to notice how the shift cable fits inside of the shifter. Re-assenbly is best done using three hands.

For personal bikes, like Bill Kapaun, I prefer to replace the MRX shifters with low end Shimano EZ-Fire shifters (and new handgrips). For customer bikes it's more labor cost effective to replace the whole shifter because new ones come with new cables already installed.

LesterOfPuppets

Not my experience with MRX. This is the cable replacement procedure for one style of MRX:

fietsbob

You didn't get the same ones as fitted on a "GMC' Denali" I expect..

LesterOfPuppets

Do they click? There should be fairly solid sounding clicks as you progress through the gears. See video two posts above this one.

If they don't properly click I suspect missing or improperly positioned metal clip that another poster mentioned.