I just rebuilt (made new again) the 3 spd/OD (T89) in the 56J. I installed it NOS about 35 years and 170,000 miles ago. It was manufactured late 1963, so was on the shelf about 23 years before I got it from Lester Schmidt. It's always been trouble free, but about 5000 miles ago developed a light growl, under load in 2nd gear, and under decel in 3rd; in or out of OD had no effect, so I was pretty sure the problem was within the main case. Upon tear down, the main case rear bearing (middle of 3 bearings) was obviously on its way out; the front (a.k.a. input shaft) bearing, and tail shaft (rear most) bearing were both OK. Over the decades, I'd occasionally grind the (unsynchronized) 1st gear, not often, but accumulation took its toll. So the cluster gear's 1st gear cog was chewed up, and its metal fragments were on the case floor. The growl's source was the bearing, but it is adjacent to the 1st gear cog, so my theory is some of the metal fragments got in the bearing at some point. To avoid this in future, I installed magnetic drain plugs.
The transmission is designed with only about .005" clearance between the OD ring gear and OD case. When any of the 3 bearing begin to fail, the ring gear begins making light contact with the case, which amplifies the noise. Glad I took action sooner than later, which resulted in minimal damage.
Several internal components interchange with early T10: synchronizer rings; front & rear case bearings; cluster gear shaft & bearings; input shaft-to-main shaft junction needle bearings, so I bought those all in a T10 kit. I replaced all three shaft bearings, the cluster gear and it's shaft (NOS on eBay) and bearings, and the 1st/reverse slider gear (also NOS off eBay). The synchronizers were as new, so I left them alone. Of course I replaced all seals and gaskets; fabricated the gaskets, and measured each seal and bought them off eBay, by size. I even found a rear yoke seal (National #4889) to replace the long NLA rawhide seal.
Compared to T86, the T89/T85 is not easy to work on, and it does not help that some procedures in the Stude Shop Manual are flat out wrong. It probably took me 15 hours' labor, but I could probably do another in half that time. The real PITA was removal and reinstallation in the 56J. Due to a 50 cent clutch T/O bearing retractor spring, it is necessary to remove and reinstall the transmission with bell housing attached. But I fabricated a different retractor spring (copied off the GM classic car guys), so I could reinstall them separately, which helped tremendously.
For oil, I initially used Royal Purple GL-5, 75W90, which says on the label it is safe for yellow metals. It was available at FLAPS, and I thought I was out of Red Line MT-90. Then I drove the car 50 miles, and thought I'd done something wrong in the rebuild; shifting was tight, even the OD upshift was more pronounced. I then found two quarts of MT-90 I'd forgotten I had. So drained Royal Purple and replaced it with MT-90. The transmission was instantly transformed back to its old self, with smooth and easy shifts.
I am mainly posting this thread mainly for our archives, and titled it T89/T85 because, AFAIK, all rebuild procedures are identical, though some gears, and rear main shaft are different.
The transmission is designed with only about .005" clearance between the OD ring gear and OD case. When any of the 3 bearing begin to fail, the ring gear begins making light contact with the case, which amplifies the noise. Glad I took action sooner than later, which resulted in minimal damage.
Several internal components interchange with early T10: synchronizer rings; front & rear case bearings; cluster gear shaft & bearings; input shaft-to-main shaft junction needle bearings, so I bought those all in a T10 kit. I replaced all three shaft bearings, the cluster gear and it's shaft (NOS on eBay) and bearings, and the 1st/reverse slider gear (also NOS off eBay). The synchronizers were as new, so I left them alone. Of course I replaced all seals and gaskets; fabricated the gaskets, and measured each seal and bought them off eBay, by size. I even found a rear yoke seal (National #4889) to replace the long NLA rawhide seal.
Compared to T86, the T89/T85 is not easy to work on, and it does not help that some procedures in the Stude Shop Manual are flat out wrong. It probably took me 15 hours' labor, but I could probably do another in half that time. The real PITA was removal and reinstallation in the 56J. Due to a 50 cent clutch T/O bearing retractor spring, it is necessary to remove and reinstall the transmission with bell housing attached. But I fabricated a different retractor spring (copied off the GM classic car guys), so I could reinstall them separately, which helped tremendously.
For oil, I initially used Royal Purple GL-5, 75W90, which says on the label it is safe for yellow metals. It was available at FLAPS, and I thought I was out of Red Line MT-90. Then I drove the car 50 miles, and thought I'd done something wrong in the rebuild; shifting was tight, even the OD upshift was more pronounced. I then found two quarts of MT-90 I'd forgotten I had. So drained Royal Purple and replaced it with MT-90. The transmission was instantly transformed back to its old self, with smooth and easy shifts.
I am mainly posting this thread mainly for our archives, and titled it T89/T85 because, AFAIK, all rebuild procedures are identical, though some gears, and rear main shaft are different.
It is well to trust but verify.
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