I'm going on my third day of bed rest dealing with the worst flu/cold I've ever had. Half conscious and heavily sedated I thought it would be a good time to share my story. This is a long one so I won't feel bad if you don't read it lol.
Back in 2010 I bought my 91 Crew Cab. One of the first things I noticed during the test drive was the excessive transmission/clutch noise. Looking over the service history I noticed the clutch had been replaced and transmission had been rebuilt at 164k miles. It was showing somewhere around 215-220k when I signed the title. So the clutch lasted 50 or so thousand miles huh... Anyway I knew the DMF had a bad reputation and I was working 7 day weeks so I paid a reputable shop to swap the clutch out to a South Bend with the single mass flywheel.
I picked my truck up from the shop and the owner showed me the old DMF which was about to grenade. That's when he told me my transmission was making a LOT of noise. He said this was one of many SMF conversions he's done but none of them sounded like this. He felt bad (we both figured the noise was coming from the flywheel) and told me he would cut me a good deal on rebuilding the transmission if I decided to go that route. Well during the ride home I thought the transmission was going to explode--literally explode. I drained the oil and it looked really bad. I decided to go a different route and top it off with a 50w industrial oil from Mobil that was a similar viscosity as 50w ATF. Now the transmission was only noisy when lugging it or driving at slow speeds---fair enough. I turned up the idle and that helped a little bit. Cold weather shifting took some getting used to.
I've never ridden in another IDI with this combo so I didn't know what to think.. After searching to the end of the interwebs I decided the noise was probably normal. Everyone seemed to agree the SMF makes the ZF5 noisy so for the last 30,000 miles I have tried my best to ignore it. Fast forward to December 2013. A friend bought a 91 IDI like mine and a week later locked up and exploded the input bearing in the trans. If figured I'd better check my oil...
Unscrew the fill plug. Nothing. Dip the short end of the allen wrench in. Nothing. Dip the long end of the allen wrench in. Nothing. Drain the trans and find less than two quarts of oil come out... You're kidding me right? Not once have I seen a drop of oil on the driveway and I know I filled it all the way full. I figured it pumped into the transfer case. I check the t-case and it was right were it needed to be. Uh
Pissed off and wondering what kind of permanent damage I did to the trans I go to Wally World and buy the cheapest ATF they have. I fill it up then try to reinstall the shifter boot and completely destroy it--ugh. I decide I don't have time to fiddle with it and just bought a new boot from the dealer. $90 later I have a completely upgraded-redesigned boot that looks to be 100 times better than the original. Fresh ATF. Check. New shifter boot with upgraded sound dampening features. Check.
Now the part you'e been waiting for: It's a whole new truck. Transmission is quiet and I do mean QUIET. Even at an idle with the clutch out it I can barely hear roll-over. No more moaning and groaning rattle and shake and it shifts great
It went from dump truck to grandpa cruiser that fast.
Moral; Use ATF in a ZF5 (because that's what it was designed for....weird) and check the level often. Oh and $90 is a lot of money don't get me wrong but that newer boot design is a winner.
Back in 2010 I bought my 91 Crew Cab. One of the first things I noticed during the test drive was the excessive transmission/clutch noise. Looking over the service history I noticed the clutch had been replaced and transmission had been rebuilt at 164k miles. It was showing somewhere around 215-220k when I signed the title. So the clutch lasted 50 or so thousand miles huh... Anyway I knew the DMF had a bad reputation and I was working 7 day weeks so I paid a reputable shop to swap the clutch out to a South Bend with the single mass flywheel.
I picked my truck up from the shop and the owner showed me the old DMF which was about to grenade. That's when he told me my transmission was making a LOT of noise. He said this was one of many SMF conversions he's done but none of them sounded like this. He felt bad (we both figured the noise was coming from the flywheel) and told me he would cut me a good deal on rebuilding the transmission if I decided to go that route. Well during the ride home I thought the transmission was going to explode--literally explode. I drained the oil and it looked really bad. I decided to go a different route and top it off with a 50w industrial oil from Mobil that was a similar viscosity as 50w ATF. Now the transmission was only noisy when lugging it or driving at slow speeds---fair enough. I turned up the idle and that helped a little bit. Cold weather shifting took some getting used to.
I've never ridden in another IDI with this combo so I didn't know what to think.. After searching to the end of the interwebs I decided the noise was probably normal. Everyone seemed to agree the SMF makes the ZF5 noisy so for the last 30,000 miles I have tried my best to ignore it. Fast forward to December 2013. A friend bought a 91 IDI like mine and a week later locked up and exploded the input bearing in the trans. If figured I'd better check my oil...
Unscrew the fill plug. Nothing. Dip the short end of the allen wrench in. Nothing. Dip the long end of the allen wrench in. Nothing. Drain the trans and find less than two quarts of oil come out... You're kidding me right? Not once have I seen a drop of oil on the driveway and I know I filled it all the way full. I figured it pumped into the transfer case. I check the t-case and it was right were it needed to be. Uh
Pissed off and wondering what kind of permanent damage I did to the trans I go to Wally World and buy the cheapest ATF they have. I fill it up then try to reinstall the shifter boot and completely destroy it--ugh. I decide I don't have time to fiddle with it and just bought a new boot from the dealer. $90 later I have a completely upgraded-redesigned boot that looks to be 100 times better than the original. Fresh ATF. Check. New shifter boot with upgraded sound dampening features. Check.
Now the part you'e been waiting for: It's a whole new truck. Transmission is quiet and I do mean QUIET. Even at an idle with the clutch out it I can barely hear roll-over. No more moaning and groaning rattle and shake and it shifts great
It went from dump truck to grandpa cruiser that fast. Moral; Use ATF in a ZF5 (because that's what it was designed for....weird) and check the level often. Oh and $90 is a lot of money don't get me wrong but that newer boot design is a winner.
). I keep thinking maybe it got hot and pushed fluid out but it doesn't really make sense. If a seal was blown I'd see bright red ATF everywhere... Well I'll keep a very close eye on it anyway and hope for the best. 
(maybe I'll try putting one in over the factory boot someday?)
