SRAM Eagle Transmission: full-mount install, chain length, AXS pairing and MicroAdjust

How to confirm you have an Eagle Transmission derailleur

A Transmission derailleur has no hanger. It clamps straight onto the frame at the UDH (Universal Derailleur Hanger) pocket, with a big 8 mm bolt running through the middle and a knurled ring around it. You will also see a Setup Key marked A and B on the side of the body, and a Cage Mode button. There are no limit screws and no B-tension screw. If your derailleur has those screws and hangs from a hanger, it is a standard Eagle derailleur; see the GX Eagle mechanical page instead.

SRAM model numbers read like RD-XX-E-B1: RD for rear derailleur, XX for the series, and B1 for second generation, first version. The family splits into two groups:

• AXS wireless: RD-XX-SLE-B1 (XX SL), RD-XX-E-B1 (XX), RD-X0-E-B1 (X0), RD-GX-E-B1 (GX) and RD-S1000-E-A1 (S1000). These take an AXS battery and shift from a Pod controller.
• Mechanical, with a cable: RD-90-A1 (Eagle 90) and RD-70-A1 (Eagle 70). They use the SL-90 or SL-70 trigger shifter and a 1.1 mm stainless shift cable. They have no battery and do not pair.

The serial number on an AXS Transmission derailleur is laser etched on the underside of the B-knuckle. On Eagle 90 and Eagle 70 it is etched under the Setup Key housing. Enter the serial number at sram.com/service to get the exact model. On a SRAM 12-speed chain, the date code is above the round hole on the PowerLock and on the outer plates of the chain.

The frame must be built to the UDH standard with the required clearances, and the rear axle must be a bolt-type thru axle with a 12 x 1.0 mm thread. Quick release wheels will not work.

Specifications

On e-MTBs, multi-shift is off by default and can be turned on in the AXS app under Drivetrain Settings. SRAM says the XX SL chain (CN-TTYP-XXSL) and XX SL cassette (CS-XS-1299) are not designed for e-MTB use, and Eagle 90 or 70 derailleurs on an e-MTB must be used with the SRAM Single Click shifter.

Torque figures

The SL-90/SL-70 cover bolt and skid plate figures are very low. Use a small-range torque driver for them.

Charge and fit the AXS battery

Before you start: wash your hands or use clean gloves. SRAM warns that sunscreen or solvent cleaners on the battery can make it crack.

1. Take the cover off the battery and put the battery in the SRAM charger. The charger light is yellow while charging and green when the battery is full. Press the release button to take it out.

2. On the derailleur, open the battery latch and take out the battery block. The block protects the terminals when no battery is fitted, so keep it.

3. Push the charged battery in and close the latch. It should snap shut and the derailleur light should flash green once.

4. Use only the SRAM charger. For anything beyond charging and fitting, follow the SRAM Battery and Charger User Manual.

   From the SRAM Transmission user manual, SRAM Battery Charging

For long storage or transport, take the battery out and fit the battery block and cover. Store the battery at 50% charge or more. Take the battery out and fit the block before you wash the bike, and do not use a pressure washer on AXS parts. A swapped battery does not need re-pairing.

Chain length, Setup Key and Setup Cog

Transmission does not use a chain gap gauge. Instead, each frame has three settings: a chain length, a Setup Key position (A or B) and a Setup Cog (21T or 24T). SRAM's Full Mount Chain Length Guide and the SRAM AXS app give all three for listed frames. SRAM says the online guide is the most accurate source, and the printed chain length table in the manual may differ from it, so use the guide.

Before you start: a wrong Setup Key position gives the wrong chain gap and can damage the derailleur or frame. Look it up for your exact frame and size.

1. Look up your frame in the Full Mount Chain Length Guide or the AXS app and write down the chain length, Setup Key position and Setup Cog.

2. A new aftermarket T-Type chain has 126 links. Count down from 126 to the length the guide gives and break the chain at an inner link with a chain tool approved for Flattop chains. Some bikes need more than 126 links: join two chains with a second PowerLock and put the two PowerLocks as far apart as possible.

3. Tighten the cage onto the derailleur body. This moves it from the position it ships in.

4. Pry the Setup Key out with a small flathead screwdriver, turn it to A or B, and push it back in so its notch lines up with the matching line on the body.

5. AXS models: press the top button on the Pod controller (or tap the derailleur AXS button repeatedly) until the derailleur is fully outboard. Then press the bottom button five times for the 21T cog (gear 7) or six times for the 24T cog (gear 6). A quick double press of the derailleur AXS button also sends it inboard to the Setup Cog position.

6. Eagle 90/70: push the parallelogram inboard by hand until the hexagon-shaped cutout shows between the fins. Push a straight 4 mm hex key (21T, gear 7) or 5 mm hex key (24T, gear 6) into the cutout to hold it there. Do not use a ball-end or rubber-coated key, and do not twist the key in the cutout.

   From the SRAM Transmission user manual, Prepare (AXS and mechanical)

If your frame is not in SRAM's database, use Setup Key A and the 21T Setup Cog (gear 7), and do the tightening step with the bike at sag. For frames with an idler pulley, wrap the chain over the big chainring, the idler and the largest cog with the shock fully compressed, then add one inner and one outer link where the ends overlap. More on sizing in general is on the chain length page.

Install the derailleur on the frame

Before you start: the cage is spring loaded and snaps back fast when it comes out of Open Mode. Hold it from the outside and keep fingers away from the pulleys. Power off an e-bike before you put the chain on.

1. Remove the UDH. Its bolt is left-hand threaded, so turn it clockwise with an 8 mm hex key to loosen it. Take out the bolt and washer, rotate the hanger backward out of its pocket and remove it.

2. Take the mount bolt and the bushing frame insert off the derailleur. Clean grease and dirt out of the frame pocket, then push the bushing frame insert into the frame from the outside, black side facing out. On split-pivot frames, fit the washer between the pivot bearings.

   From the SRAM Transmission user manual, Prepare

3. Turn the knurled ring clockwise until it touches its stop. The stop has to sit between the two horns on the ring.

4. Grease the mount bolt threads and the underside of the bolt head.

5. Slide the full mount over the frame pocket and insert, thread the mount bolt in clockwise until snug, then back it off one full turn.

6. Rotate the cage forward until the lock icon clears the Setup Key and press the Cage Mode button to lock the cage in Open Mode.

7. Grease the thru-axle threads, fit the wheel, snug the axle, then loosen it one full turn. SRAM says the axle must be loose here or the install will be wrong. It gets torqued at the end.

8. Put the cut chain on the Setup Cog and through the pulleys, with the flat side of the chain facing away from the cassette and the chain below the tab in the cage. Make sure it sits down on the cog teeth.

9. Join the ends with a new PowerLock, arrow pointing the way the chain travels.

10. Rotate the cage forward to release the Cage Mode button, then let the cage settle until the button locks where the two key lines meet. This is Setup Mode.

11. Turn the crank until the PowerLock is above the chainstay, check both halves line up, then close it with chain link pliers or by holding the rear brake and pushing down hard on the crank until it clicks. Check that the link moves freely. A PowerLock is single use.

    From the SRAM Transmission user manual, Hang the Components

12. Check before you tighten: axle and mount bolt each one turn loose, Setup Key in the right position, derailleur in Setup Mode (on Eagle 90/70 the hex key is still in the cutout), chain on the Setup Cog and on every tooth, PowerLock closed, and rear suspension at 0% sag unless your frame needs sag.

13. Pull back on the lower cage to take up chain slack. Keep pulling while you turn the crank forward two full turns and check the chain stays on the Setup Cog. With a 24T Setup Cog, make sure the chain sits fully on the cog's tooth profile.

14. Still pulling back on the cage, tighten the mount bolt to 35 N·m (310 in-lb) with a torque wrench, then let go. If there is still slack, loosen and do it again.

15. Check that the mark on the knurled ring lines up with the mark on the full mount. If it does not, loosen the mount bolt one turn, turn the knurled ring back against its stop, and repeat the last two steps.

16. Torque the thru axle to the frame or axle maker's figure.

17. Rotate the cage forward and ease it back to release it from Setup Mode into Ride Mode.

18. Eagle 90/70 only: push the parallelogram inward to free the hex key and pull it out. Leaving it in can damage the derailleur. Turn the crank so the chain moves fully outboard to gear 12, then go to the cable setup.

    From the SRAM Transmission user manual, Tighten the Components

There are no adjustment screws to set afterwards. Do the whole install again if you change chainring size, change chainstay length with a geometry adjustment, move a lower idler, or fit a new chain.

Pair the derailleur and Pod controller

The derailleur starts and ends each pairing session. Pair again whenever you add, remove or replace a component. Swapping a battery does not need re-pairing.

1. Press and hold the AXS button on the derailleur until its light blinks slowly, then let go.

2. Press and hold the AXS button on the controller until its green light blinks quickly, then let go. With two controllers, pair the right one first. The first one paired acts as the right-side controller.

3. Press and release the derailleur AXS button to end the session, or wait 30 seconds for it to time out.

4. Open the SRAM AXS app and check that the controllers are listed under the derailleur.

   From the SRAM Transmission user manual, System Pairing

To fit a Pod on a Discrete or Infinity clamp, loosen the T25 clamp bolt, line up the Pod's pointed tip with the open slot, set the position and angle, and tighten to 2 N·m (18 in-lb). Check that the Pod does not get in the way of the brake lever.

Final check and MicroAdjust

1. Turn the cranks slowly and shift all the way inboard with the bottom Pod button, then all the way outboard with the top button. If you forgot to release the cage, it releases into Ride Mode on its own as it shifts inboard. The pulleys look out of line with the cogs on purpose.

2. Set the rear suspension to sag. If shifts to bigger cogs are slow, hold the controller AXS button and press the lower button to move the derailleur 0.2 mm inboard. If shifts to smaller cogs are slow, hold the AXS button and press the upper button to move 0.2 mm outboard. The light blinks with each press. You can also do this in the AXS app.

3. MicroAdjust moves the derailleur for all cogs at once. Make changes only with the bike standing still, then test ride. Never adjust while riding.

   From the SRAM Transmission user manual, Final Check (AXS)

If shifting feels rough in the stand but fine on the trail, that is expected on a full-suspension bike: with the suspension fully extended in a stand, the chain gap is smaller than the setup intends. Judge shifting at sag.

Eagle 90 and Eagle 70 cable setup

The mechanical Transmission derailleurs need a 1.1 mm stainless steel cable and 4 mm compressionless housing. Replace cable and housing together at least every 200 hours of riding.

1. Turn the shifter barrel adjuster clockwise until it stops.

2. Cut the housing so it bends gently and lets the bar turn about 120 degrees each way. Fit metal ferrules at both ends and seat them fully in the barrel adjuster and the derailleur cable stop. Avoid long loops at the derailleur.

3. Lock the cage in Open Mode. Run the cable through the housing, the roll-a-majig and the actuation fin (through the fin tab), then under the clamp groove and anchor bolt, pulled tight along the groove.

4. Holding the cable tight, press the shifter release lever until the shifter is in gear 12. Keep it in gear 12 for the next steps. Release the cage from Open Mode.

5. Pull the cable tight without pushing the parallelogram inboard, and tighten the T25 anchor bolt to 4.5 N·m (40 in-lb).

6. Pedal and turn the barrel adjuster counter-clockwise to add tension until the chain runs quietly on the 10T cog (gear 12). Shift to the 12T (gear 11) and adjust until quiet, then shift back and check the shifts are crisp. If you need more than 7 full turns counter-clockwise, start the routing again and check the ferrules, gear 12 and cable slack.

7. Cut the cable about 30 mm past the anchor bolt, crimp on an end cap and tuck the end behind the actuation fin.

8. Fine tuning, at sag and standing still: for slow shifts to bigger cogs, turn the barrel adjuster counter-clockwise one click at a time. For slow shifts to smaller cogs, turn it clockwise one click at a time.

   From the SRAM Transmission user manual, Cable Routing and Final Check (mechanical)

To change the cable in an SL-90 or SL-70 shifter: shift to the 10T cog (gear 12), cut off the end cap and loosen the T25 anchor bolt. Push the cable into the shifter to free the head and pull it out, then feed the new cable in until the head sits in its pocket and do the routing above. If the cable will not come out or has broken inside, remove the cover bolts, take off the cover, swap the cable and refit the cover at 0.4 N·m (3.5 in-lb).

Remove and refit the rear wheel

1. Rotate the cage forward and press the Cage Mode button to lock it in Open Mode. This gives slack to take the wheel out and put it back.

2. Before you tighten the thru axle, release the Cage Mode button so the derailleur goes back to Ride Mode. If you tighten the axle first, the derailleur can be clamped in the wrong position.

   From the SRAM Transmission user manual, Rear Wheel Change

Replace the pulley wheels

Before you start: the cage is under spring tension. Hold it from the outside when you take it off.

1. AXS: shift to the 21T Setup Cog. Eagle 90/70: hold the Setup Cog position with a 4 or 5 mm hex key in the parallelogram cutout.

2. Hold the derailleur body and turn the cage clockwise until it comes free of the P-knuckle, then take it off.

3. Remove the T25 pulley bolts, the pulleys and the spacers (AXS) or bushings (Eagle 90/70).

4. Fit the new pulleys facing the way the manual shows, refit the spacers or bushings flat side out, and tighten the pulley bolts to 3 N·m (27 in-lb).

5. Put a light coat of grease on the clutch spring and refit the cage into the P-knuckle.

   From the SRAM Transmission user manual, Cage Pulley Wheel Replacement

Replace the chain

1. Check wear with a SRAM-approved chain checker. Replace the chain at 0.8% elongation.

2. Shift to the smallest cog, lock the cage in Open Mode, open the PowerLock with chain link pliers and take the chain off.

3. Size the new chain and repeat the full install from Prepare through Tighten. SRAM lists a new chain as a reason to redo setup. Always use a new PowerLock.

   From the SRAM Transmission user manual, Chain, Cassette and Chainring Replacement

Clean the drivetrain only with pH-neutral cleaners (pH 6–8). SRAM warns that strong acid or alkaline cleaners can make parts brittle enough to break. If shifting is still poor after heavy use and nothing else explains it, replace the chainring, chain and cassette together.

Parts and consumables

Tools

• 8 mm hex key (mount bolt and UDH bolt)
• Straight 4 mm and 5 mm hex keys, not ball-end (Eagle 90/70 Setup Cog hold)
• 2 mm and 2.5 mm hex keys, T20 and T25 Torx, 3 mm security hex bit, PH00 Phillips
• Small flathead screwdriver (Setup Key)
• Chain tool approved for SRAM Flattop chains, and chain link pliers (PowerLock)
• Chain whip and cassette lockring tool with guide pin (splines 7–8 mm long for XD/XDR)
• Torque wrench covering 35 N·m, plus a low-range torque driver
• Cable cutter (Eagle 90/70)
• SRAM-approved chain wear checker

No chain gap gauge is needed. The Setup Key on the derailleur does that job.

Troubleshooting by symptom

Derailleur does not shift and its light is off

Derailleur battery flat, controller battery flat, system not paired, or the firmware has stalled. Charge or replace the batteries, pair again, or take the battery out and put it back in.

Light blinks red and green when you shift

The shift was rejected. Below -15 °C (5 °F) shifts can be rejected.

Slow shifts to bigger or smaller cogs (AXS)

Trim is off. Use MicroAdjust at sag.

Slow shifts on Eagle 90 or 70

Cable tension is wrong. Turn the barrel adjuster one click at a time as in the cable setup.

Slow shifting you cannot tune out

Check the thru axle is torqued, the mount bolt is at 35 N·m, the cassette is at 40 N·m, the drivetrain is clean and lubed, and the chain, cassette and upper pulley are not worn. If the chain gap is too big, redo the install on the Setup Cog with the knurled ring against its stop.

Rasping noise you cannot tune out

Loose axle, chain gap too small, wrong chain length, dirty drivetrain or worn cassette.

Chain bounces on the small cogs

Chain too long, or the cage damper has lost tension and the cage needs replacing.

Chain very tight on the biggest cog, or derailleur hits the frame

Chain too short. Check the length against the SRAM guide.

Chain skips under load

Dirty drivetrain, chain gap too big, chain too long, low damper tension, or a worn chain or cassette.

Shifting is rough in the stand but fine on the trail

Normal on a full-suspension bike hanging fully extended. Check shifting at sag.

Related: SRAM GX Eagle mechanical, Set chain length, Adjust a rear derailleur, SRAM DB8 brakes