45RFE and 545RFE Gear Ratios and Specs: Ratios, Clutch Chart, Clearances and Torques

People ask me for "the 45RFE specs" as if there were one number. What they usually want is one of four things: the gear ratios so they can figure out cruise RPM after a tire or axle change, the clutch application chart so they can figure out which pack is slipping, the endplay and clutch clearances because the unit is on the bench, or the torque values because the pan is off. This page puts all four in one place, straight from Chrysler's service information for the RFE, with the source for every number at the bottom.

One note before the tables. The 45RFE and 545RFE share the same gear train. MOTOR described the 45RFE at launch as a four-speed with a reverse gear, built on three simple planetary gearsets instead of a compound Simpson set, with an alternate second gear used on downshifts above certain speeds (MOTOR, June 2000). The 545RFE adds a fifth ratio. Chrysler's 545RFE spec table is what I quote below, and everything except fifth gear applies to the 45RFE too. Chrysler revised parts over the production run, so check the service information for the year on your bench before you trust any clearance to the thousandth.

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45RFE and 545RFE Gear Ratios

Chrysler lists these ratios for the 545RFE (Chrysler 545RFE Description, Chrysler 545RFE Specifications):

The step column is just the lower ratio divided into the higher one, and it explains how these units feel. The 1-2 step is big at 1.80, which is why a worn 2C pack or a lazy 1-2 shift shows up as a flare you can hear. The 4-5 step on a 545RFE is small at 1.12, so a lot of owners never notice fifth coming in at all.

What 2nd prime is for

Chrysler explains it plainly: the primary 2nd gear sits between 1st and 3rd for normal acceleration through the gears, and the alternate 2nd (2 prime) gives smoother 4-2 kickdowns at high speed so you get second-gear passing over a wider highway range (Chrysler 545RFE Description). Going from 0.75 straight to 1.67 at 65 mph would spin the engine way up and jerk the truck. Dropping to 1.50 gives a smaller jump. MOTOR described it the same way in 2000: 2nd prime comes in on downshifts above certain vehicle speeds (MOTOR, June 2000). On an upshift from a stop, you never see 2nd prime.

Watch for this on ERS trucks. Chrysler notes that vehicles with Electronic Range Select display as if the transmission were a six-speed, with 2nd prime shown as third, third as fourth, and so on (Chrysler Road Testing). If a customer says their truck "skipped a gear" or "has six speeds," that is usually why.

What the Ratios Mean at the Wheels

Multiply the transmission ratio by the axle ratio to get the overall ratio. For engine RPM at a given speed, use RPM = MPH x overall ratio x 336 / tire diameter in inches. Here is what that gives on two common Ram and Durango axle ratios with a 31-inch tire, assuming the converter is locked in the top gears:

First gear works out to 10.65:1 overall with 3.55 gears and 11.76:1 with 3.92s. Bigger tires lower all of these, which is why a lifted truck on 33s with factory 3.55s feels lazy and hunts between 4th and 5th on the highway. That hunting means extra heat and extra clutch cycles, and it is one of the reasons I push people toward the axle ratio that suits the tire. Our 45RFE towing upgrades guide goes deeper on that.

Clutch Application Chart

This is the chart I use most. The RFE has three input clutches (underdrive, overdrive, reverse) and three holding clutches (2C, 4C, low/reverse), plus an overrunning clutch for first (Chrysler 545RFE Description). Chrysler's application chart (Chrysler Road Testing):

How to use it: most clutches work in more than one forward gear, so a slip that shows up in two gears sharing a clutch points straight at that clutch. Slips in 2nd and 5th? Both use 2C. Flare into 4th, and the high-speed 4-2 kickdown feels soft too? Both 4th and 2nd prime use 4C. Slips in 3rd, 4th and 5th but 1st and 2nd are fine? OD is the one common factor. Chrysler builds its pressure test on the same idea: if you suspect an element, check pressure in at least two gear positions that use it (Chrysler Hydraulic Pressure Test).

The limp-in rows matter too. Chrysler says the hydraulic system alone gives Park, Reverse, Neutral, 2nd and 3rd by shift lever position, so the truck can still move if the electronics fail. Trucks with ERS (Chrysler lists WK, WH, XK and XH) do not get 2nd in limp-in because the lever has no 2 or 1 position (Chrysler 545RFE Operation). So "stuck in 3rd" on a 45RFE is usually the default gear, not a broken part. Start with codes; the limp mode guide covers what to look for.

Solenoid pack connector color tells you the generation

Before you order a valve body or solenoid pack, check the connector color, because it tells you which generation of control hardware is on the bench. Sonnax's technical write-up on RFE universal valve bodies documents three distinct designs across the family's production run: the original black connector design, a white connector design Chrysler introduced in 2004 when it switched to internal solenoids specifically to reduce operational noise, and a grey connector design added in 2010 for the 65RFE, 66RFE and 68RFE that eliminated the dedicated overdrive solenoid, folding that function into the multi-function solenoid instead. A solenoid pack and valve body have to be matched to the correct connector generation, not just the transmission model, which is why Sonnax built its universal CHR145/CHR146 remanufactured valve bodies to accept any of the three colors rather than make a shop stock three separate part numbers.

Endplay and Clutch Clearances

From Chrysler's 545RFE specification table (Chrysler 545RFE Specifications):

Measure input endplay before teardown, not only at assembly. A reading past the top of the range on a unit that came in with a complaint tells you a thrust surface or bearing is worn, and you want to find it before you order parts. On clutch clearances, I set new packs toward the middle of the range, not the loose end. The TCM learns fill volumes, but a pack sitting at the maximum gap takes longer to fill and gives the adaptives more to make up. After any clutch work, do the quick learn. ATRA notes it resets more than 70 learn parameters to their base values (ATRA Technical Bulletin 990).

You can also air check the packs before the unit goes back in. Chrysler calls for clean, dry air at 30 psi at each apply passage with the pan and valve body off. A working clutch gives a soft thump when it applies and should release when you let off the air (Chrysler Air Checking Clutch Operation).

Pressure Specs

The RFE uses closed-loop line pressure, so Chrysler warns that readings can vary a lot but should always follow line pressure. Test at normal operating temperature, full fluid, 1500 rpm. The scan tool line pressure reading should match a gauge within plus or minus 10 psi. The only case ports are TCC apply and release; everything else needs the pan off and adapter 8258-A on the valve body (Chrysler Hydraulic Pressure Test). Chrysler's published targets for the 545RFE:

• Garage shifts: N-R 220 psi (4.7L) or 250 psi (5.7L); R-N 120 psi; N-1 135 psi (4.7L) or 165 psi (5.7L).
• In-gear maximum: 1st 135 psi (4.7L) / 160 psi (5.7L); 2nd, 2nd prime, 3rd, 4th and 5th 120 psi (4.7L) / 135 psi (5.7L); Reverse 220 / 250 psi.
• TCC lockup: 120 psi (4.7L), 125 psi (5.7L).

A 45RFE behind a 3.7L or 4.7L on an earlier calibration may not match these exactly, but the method is the same: compare gauge to scan tool, then compare the gears that share a clutch.

Fluid and Capacities

Mopar ATF+4 is the specified fluid (Chrysler 545RFE Specifications). Castrol's own Transmax ATF+4 product data sheet confirms this independently: it lists the fluid as licensed to the Chrysler ATF+4 specification for Chrysler automatic transmissions, which is the same spec Ram's service information calls out for the 45RFE and 545RFE. Ram lists the 45RFE and 545RFE service fill at 5.2 liters (11 pints) for 4x2 and 6.2 liters (13 pints) for 4x4, and a dry overhaul fill of 14 to 16 liters (29 to 33 pints) depending on the cooler setup (Ram Body Builder 2008 fluid capacities). Set the final level on the dipstick, not by the number. The full procedure is in our 45RFE fluid type and capacity guide.

Torque Specs You Will Actually Use

From the same Chrysler table (Chrysler 545RFE Specifications):

Almost everything inside the case is inch-pounds. The valve body and solenoid screws go into aluminum, and the pan rail warps if you lean on it. Use an inch-pound wrench for the whole top half of this list. The cooler return filter value above is from the 2007 table; the service bulletins that changed that filter call out their own install values, so follow the bulletin if you are doing that job.

Quick Reference for the Bench

1. Ratios: 3.00 / 1.67 / 1.50 (2nd prime) / 1.00 / 0.75 / 0.67 (545RFE 5th) / R 3.00.
2. Pinpoint a slip: find the clutch the two slipping gears share on the application chart.
3. Before teardown: check input endplay (0.018-0.035 in.).
4. At assembly: set each clutch pack inside its clearance range, then air check at 30 psi.
5. Install: inch-pound wrench for pan, valve body, solenoid and sensors; ATF+4 only.
6. After: quick learn, then drive it so the TCM can adapt.

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Frequently Asked Questions

What are the 45RFE gear ratios?

Chrysler lists 3.00:1 first, 1.67:1 second, 1.50:1 second prime, 1.00:1 third, 0.75:1 fourth and 3.00:1 reverse. The 545RFE uses the same gear train and adds a 0.67:1 fifth gear.

What is 2nd prime on a 45RFE?

Second prime is an alternate 1.50:1 second gear that uses the underdrive and 4C clutches. Chrysler uses it for 4-2 kickdowns at highway speed, so the downshift is smoother than dropping all the way to the 1.67:1 second gear. You will not see it on a normal upshift from a stop.

What is the difference between 45RFE and 545RFE gear ratios?

There is no difference in the shared gears. Both have 3.00, 1.67, 1.50, 1.00 and 0.75 forward ratios and a 3.00 reverse. The 545RFE adds a 0.67:1 fifth gear, applied with the overdrive and 2C clutches.

What fluid and how much does a 45RFE take?

Mopar ATF+4. Ram lists a service fill of 5.2 liters (11 pints) for 4x2 and 6.2 liters (13 pints) for 4x4, and a dry overhaul fill of 14 to 16 liters depending on the cooler. Set the final level on the dipstick in Park with the engine idling.

What is the 45RFE input shaft endplay spec?

Chrysler's RFE specification table lists input shaft endplay at 0.018 to 0.035 inch (0.46 to 0.89 mm) and output shaft endplay at 0.009 to 0.021 inch (0.22 to 0.55 mm). Check the service information for the exact model year on your bench.