Printable View
I hope to get some advise.
2003 Silverado 2500HD LB7 with Allison transmission.
I have what looks like a front trany seal leak.
This requires the removal of an ally that has 208k miles on it. (to my knowledge)
Should I refresh it or do anything while it is out?
I was thinking of the 6th gear kit for better economy. Yet that is only good when I am not hauling something.
I would like opinions please...
GM identified the source of an ATF leak in mid 2003, and issued service bulletin no. 03-07-30-057 in response. This bulletin discussed a possible leak source as being the two lower torque converter housing bolts. Until the Allison production week of September 8, 2003, these bolts were not sealed to prevent ATF leaks. After that date, Allison began installing a copper washer (pn-10139097) beneath each bolt head. Transmissions shipped before that date were assembled without the copper washers, and a few individual transmissions leaked ATF due to case porosity issues. If the threads of the bolts are wet with ATF when removed, the copper washers should effectively seal the bolt and prevent future leaks.
In addition to the copper washers, Allison techs recommend sealing the bolt threads using a dab of Teflon paste, along with a small amount of silicone gasket sealing compound on both sides of the copper washer, before torquing each bolt to 42 ft/lbs.
I had to R&R an Allison a few years ago because of this very problem. While you're in there, I'd replace the front seal as well, but I'd not worry about refreshing the transmission unless it's seen hard use with performance programming or you suspect something else might be wrong.
Secondarily... If the transmission in this truck has been out before, you should verify that the steel alignment dowels on the aluminum adapter (that the trans actually bolts to) are there and undamaged. These steel dowels align the transmission to the crank centerline. If the dowels are damaged or missing, a misalignment will exist that causes chronic front seal failure.
Jim
I would say that it has seen hard use as a work truck for an oil well servicing company. (Key Energy Services)
Yet that does not mean that any performance programming or other power upgrades have been done.
Thank you so much for your response and I will discuss these things with my mechanic.
I would in future hope to up the HP a little in the interest of better fuel economy as the truck is intended for hauling an RV trailer. 50 to 100 more horse power with the right gadget I should think... Would that be okay?
At least for the LB7/LLY, my experience has been that the 50-100 extra hp improves towing fuel economy, in large part because the engine has the power to remain in OD more often while towing in hilly country. Simply put, kicking down and running at higher engine speeds for the time it takes to pull that hill burns more fuel. There may be some additional benefits in injection timing and fuel/boost mapping, but I think the biggest benefit is having just enough extra power to remain in OD. The performance module setting I use most while towing adds an additional 70-hp (it's been dyno'ed a few times).
I also found that with the additional power, EGTs are lower because the engine is running at a lower RPM while pulling hills with a trailer. This is so because factory turbos are more efficient and turbine drive pressures are lower at lower RPMs (in the 2000-2400 RPM range).
Jim