What type of fluid should I use in my 5spd?

[CAROLINA CUMMINS]

5w30 is the recommended lubricant for our Getrag 5spd manual transmission. Synthetic is highly favored, and one of the best things you can do for longevity or to quiet it down is to overfill it by a quart. This can be done by removing the shifter, using the top PTO cover bolt, or through the stock fill plug location with the truck sideways on a hill.



Steven

 

[dpuckett]

I can personally attest to the noise reduction by overfilling a quart. Since it is a gearbox, the extra fluid wont blow seals as it can in an auto. The reason we need to overfill above the factory recomendation is that in 5th gear, the only lubrication to the upper shaft/ cluster is by splash lubrication- the fluid literally is splashed up onto the upper gears by the lower cluster. That may be ok for running empty, or towing light, but when you hook up 15000lbs, it becomes a different story. The extra quart submerges the upper shaft gears, and thus you dont have as much problem with overheating. In addition it will also prevent the thing from running dry when operating at severe angles as well.

To further extend the life of your Getrag, dont lug the engine. The engine may have the torque to handle the load, but that doenst mean the transmission can handle it. You should actively "manage" your gear selection and lapse into complacency just because the Cummins has " monster/massive torque".

Also, and this applies to synthetics ANYWHERE- if you have a leak, get it fixed before going to synthetic. Synthetic oil/ lube is slicker and will get past bad seals easier than convential oils. I run engine oil in the transmission, though sometimes I'll go with a slightly heavier oil- say 15w40 or 5w50- depending on anticipated loads.



-DP

 

[Ridgerat]

What is the oil capacity for this transmission? Thanks. RR

 

[dpuckett]

Stock capacity is 3. 5qts. That means to "overfill" it by 1-1. 5 qt, you need 4. 5-5qts.

 

[Sri Ram]

I belive the DC manual says 3. 5 quarts (Someone correct me if I'm wrong. ). However, it is generally accepted here that overfilling by one quart will prolong the life of the Getrag.