kt_Engineer

The other possible reason for the leak could be the Helical Pinion retainer (on Mexican hat side) having a O-Ring over-sized (or bore under-size) which will cause the splashing oil from Helical gears to leak out through shim pack. The oil that leaks get accumulated around the carrier/axle-housing interface forcing you to believe that is where the leak is happening. One more leak area to check is the composite side(or Aluminum) cover on the bevel compartment cover side. It is the same O-Ring over-size/bore under-size issue on the cover that will cause O-Ring to pinch and oil to leak out accumulating around the carrier/axle housing interface. The best option in these cases will be to buy an O-Ring one size undersize and install them. The O-RING on helical pinion retainer and bevel compartment cover size are different and can be bought off-the-shelf. I am assuming you have a CRD92/93, CRD150/151 or CRD202/203 carrier.

You are looking for 25632356 - ( 88AX454) - OEM P/N.

T2180 is the 2nd generation triple countershaft transmission and has been out of production since 2002-2003 timeframe. T318 is the current production (3rd generation) 18 speed triple counter-shaft transmission. There are different versions of 18 speeds in both T200 & T300 series with slightly varying ratios (For example there is T318, T318LR, T318 21 and T318LR21; The LR's have creeper gears and 21's are capable of 2100lb-ft as against 1800 lb-ft torque engines).

The easiest thing for you to do is buy a brand new differential carrier from Dana (inherited the Eaton/Spicer axle when Roadranger partnership was dissolved). You should look at buying a DS404/405 or DST40 or DST41. All three axles have 3.70 & 4.11 ratio available. The question will be if the differentials fit in the axle housing you have. I think they might but I am not absolutely sure about it. Alternately you can buy Meritor 14x or 160 series axles. 14x has 3.70 & 4.11 ratios available.160 series has 3.73 & 4.10 ratio. You should be able to get used versions cheaper but swapping out the whole axle might not be easy. Also you will need to make sure the suspension brackets can properly bolt on with new axle housings. If they are welded brackets, the build will be much harder. Mack axles with CRD150/151 carrier has 3.79 & 4.19 ratio if you are interested in the swap. The have better pinion angles and you should not see any vibration issues.

Looks like you have a old TRL1076 or TRL1078 - 5 Speed transmission. Unfortunately, this 1st generation triple countershaft Mack transmission 5 speed (prior to T107 the T772 was a single countershaft design) had only provision for installing the PTO gear.

What 5 speed transmission model is this?

The Mack Transmissions in general do NOT have a separate PTO gear . The bottom countershaft gear (overdrive - on front box) is located to be SAE compliant and will mesh with 6-bolt and 8 Bolt PTO. This offers weight and and cost benefit when compared to an Eaton transmission. This is true with majority of Mack transmissions but there were some transmissions like TM308 which had unique PTO gear. This was due to gear mesh not being in appropriate positions to be SAE Compliant. The attachment shows PTO gear for a 5-speed transmission. In the picture below it will be the countershaft gear meshing with 2nd gear in the front box. T2050.pdf

The triple counter shaft design is lot more durable than twin countershaft (Eaton) design in general. T2180B was originally rated at 1700 lb-ft torque but can be used up to 1800 lb-ft. Lo Gear/Lo Split - 13.91:1; Reverse gear is 12.88:1; Mack T200 and T300 transmissions did have compound box synchronizer issues in the past and unfortunately the fixes were not put in place in time. But in 2010-2011 timeframe significant improvements were made to the range clutch and other components. The steel was changed from 8620H to 4320H (with higher Nickel content). The Nickel content helps the part with impact loads during dynamic shifting and can withstand abuse scenarios. The taper/dove on the teeth have also been increase on lo and high range side from 3/4 of a degree to around 2 degree. This helps the clutch proper engagement with the internal spline of the gear and keep them inplace during truck operation. The above changes along with other Synchronizer changes improved/decreased the warranty on T300 transmissions 76% over 3 years and projected to reduce it beyond 90% over 5 year period. Most of the previous failures were seen around 350k-400k miles. With these changes there should be few failures below 600k-750k miles. Unfortunately, the changes came a bit late to avoid bad reputation in the market. The attachments should help allay some of your fears with Mack transmissions in general. FSB 431-003 Range Clutch Synchronizer Components.pdf Weibull_T300_Warranty.pdf

Yes. The TM transmissions are no longer available.

Hopefully this will help. Please be aware this is a old datasheet. The T306G, TM308, TM309, TM308M & TM309M are no longer available. The T310 is good upto 1860 lb-ft and there is a new T310ME21 that is good upto 2100 lb-ft. I can provide all ratios if you are interested in a specific transmission. I can post all ratios for all available transmissions in a tabular format if required. MackMaxiTorqueEST300Trans1.pdf

You need to calculate the desired startability index based on Clutch Engagement Torque, Tire Revs/mile, overall gear ratio (transmission start gear x axle ratio) and GCW/GVW. For a typical highway truck you want to have startability to be no lower than 16% to be on safe side but if you are going to drive turnpike only (<3% grades) majority of the time, Eaton suggests a startability of 12%. I have seen one customer happy with a 10.5% startability recently. If it is a vocational truck (especially a garbage hauler) the minimum suggested startability is 25% which would require a deep axle ratio.

Yes. T313LR is same as T318LR as far as transmission goes. The only difference is the shift knob and pneumatic plumbing which prevents the high-split from engaging for T313LR. If you ever want to convert it into a T318LR all you need is to buy and shift knob, pneumatic lines and change the range/air valve for locking pin.

Mack Axles do have a Inter-Wheel Power Divider (IWPD)/Limited-Slip differential feature as an OPTION. This is unique feature not available on Meritor or Dana axles (though some After-Market solutions are available which if used will void axle warranty). IWPD works very similar to Inter-Axle Power-Divider with peanuts/wedges and CAM mechanism. The Bullgear/final Helical gear drives the cage which when spinning will force the peanuts to move up and down which in turn will spin the outer cam and inner cam. The outercam drives the left side axle shaft and inner cam drives the right side drive shaft. The IWPD will automatically torque differentiate when it senses one of the wheels spinning. The CAM mechanism will allow the non-slipping wheel to slowdown and transmits 3 times the torque to it. IWPD can work at speeds exceeding 25MPH unlike the diff. lock feature (which gets kicked out by VECU above 25MPH due to vehicle safety concerns). IWPD is available on CRD150/151, 125/126, 202/203 (previously was available on CRD95/96 carrier series too but currently is not) whereas Diff. Lock became available only with introduction of CRD150/151 & CRD125/126. IWPD does NOT have a lock-out feature like the Inter-Power Divider Lock-out (PDLO) optional feature. You can order a truck with PDLO and IWPD or PDLO and Diff. Lock but not both. The standard Mack axle offering does not have a PDLO or a IWPD or Diff. Lock. You will only get Inter-Axle Power-Divider (with out Lock-out) and a standard gear differential between the wheels. The attachment can help explain IAPD and IWPD in detail. PowerDivider.pdf

T310MLR has starting gear ratio of 27.31:1 and is a pretty popular Mack transmission. You can run side mounted PTO's in stationary mode if you pick the range neutralize feature. The other option you might want to consider is T313LR (13 forward speeds and 3 Reverse). T313LR does not have a deep crawler gear like T310MLR but has starting gear ratio is 16.42:1 and reverse starting gear is 23.98:1 (better than T310MLR reverse starting ratio of 23.96:1). You might want to cost compare and see which ones serves you better.