I recently changed fluids across all driveline components. The fluids and amounts required are as follows:
For the transmission, I performed four consecutive drain & fills in order to achieve >90% new fluid (since the total capacity is 10 quarts, a single drain & fill changes only ~60% fluid). I drove the car normally for a few hundred miles between drain & fills. Based on the fluid color, I will reduce the fluid change interval significantly moving forward. Although my transmission was not misbehaving at all (only ~36k miles on the car), the shifts became noticeably smoother with every drain & fill.
PTU oil, even though it is 75W-90 GL-5 oil, the same way as 88900401, it appears to have a different additive package. I cannot tell if the relatively high price of the PTU oil is justified, but I am certain that it is in fact different from the AC Delco standard 75W-90 gear oil (that my GM truck uses in the front differential).
Changing the fluid in the PTU requires removing a heat shield, which is not too hard. Removing the fill/level plug on the rear differential may require a particularly short hex socket - I had to create this tool because the rear sway bar is very close to the rear differential and blocking access to the plug. Everything except the transmission is to be filled just to the fill plug.
The transmission has to be warmed up to 185F - 203F in order for the fluid level to be correct when measured at the fill plug. Other than having a clean manual fluid pump and some clean hoses, the entire process is not terribly hard. The transmission does have a fill plug but on the XT4 it appears to require removal of components under the hood in order to allow access. Filling at the level check plug is fine as long as the correct fluid level is left, and the transmission is never starved from fluid.
| Transmission fluid | DEXRON VI auto transm fluid | 88865602 | 5.3-6.3 quarts (drain plug change) |
| Power transfer unit oil | PTU oil | 19351882 | 0.69 quarts |
| Rear axle gear oil | DEXRON LS | 88862624 | 0.92 quarts |
| Differential clutch fluid | Pentosin CHF | 88901975 | 0.37 quarts |
For the transmission, I performed four consecutive drain & fills in order to achieve >90% new fluid (since the total capacity is 10 quarts, a single drain & fill changes only ~60% fluid). I drove the car normally for a few hundred miles between drain & fills. Based on the fluid color, I will reduce the fluid change interval significantly moving forward. Although my transmission was not misbehaving at all (only ~36k miles on the car), the shifts became noticeably smoother with every drain & fill.
PTU oil, even though it is 75W-90 GL-5 oil, the same way as 88900401, it appears to have a different additive package. I cannot tell if the relatively high price of the PTU oil is justified, but I am certain that it is in fact different from the AC Delco standard 75W-90 gear oil (that my GM truck uses in the front differential).
Changing the fluid in the PTU requires removing a heat shield, which is not too hard. Removing the fill/level plug on the rear differential may require a particularly short hex socket - I had to create this tool because the rear sway bar is very close to the rear differential and blocking access to the plug. Everything except the transmission is to be filled just to the fill plug.
The transmission has to be warmed up to 185F - 203F in order for the fluid level to be correct when measured at the fill plug. Other than having a clean manual fluid pump and some clean hoses, the entire process is not terribly hard. The transmission does have a fill plug but on the XT4 it appears to require removal of components under the hood in order to allow access. Filling at the level check plug is fine as long as the correct fluid level is left, and the transmission is never starved from fluid.
