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broken tailshaft housing on 85 diesel transmission - help
Posted: Mon Dec 02, 2013 10:35 am
So while we were pulling the tranny it slipped and the round part right where the driveshaft slides onto the tailshaft cracked. It is the actual casing of the transmission rear housing that cracked and a few small pieces broke off. It didn't appear to be in a state of leaking but it does look like there is a seal pressed in there and it is slightly bent/dented. What other transmission will bolt up to the sd25 engine? Preferably we would keep this transmission insides and just throw a new rear casing piece on from a donor transmission, but I have no idea what other vehicles would fit this, and this appears to be a pretty rare truck.
Any help or advice would be great! Thanks[/list]
Posted: Mon Dec 02, 2013 2:31 pm
Find a gasser transmission that has the same length tail. Swap the front bell housings and you are back in business.
Posted: Mon Dec 02, 2013 4:03 pm
Don't mean to sound like I'm questioning you, but how sure are you that the tail housing will be the same bolt pattern where the two pieces bolt together? Has it been done lots before? It would just be a shame to go pull one and find out it doesn't work, as I've found a tranny out of a diesel but the guy wants way way to much fir it
Posted: Wed Dec 04, 2013 6:57 pm
Maybe the other guy doesn't want too much for it after all...
If you can't find another tailstock, the damaged one can be repaired by welding and reaming in a machine shop.
Posted: Wed Dec 04, 2013 7:27 pm
Honestly, the reason he wants to much for it is that the cost of the replacement tranny would be higher then the total cost of the truck. This is for tranny that we don't even know works.... Would be paying more for just the tailshaft housing. .... If we can't finda replacement casing for a reasonable price then the truck ends up in the scrap yard which really would be a shame
Posted: Thu Dec 05, 2013 12:15 am
krprice84 wrote:Honestly, the reason he wants to much for it is that the cost of the replacement tranny would be higher then the total cost of the truck. This is for tranny that we don't even know works.... Would be paying more for just the tailshaft housing. .... If we can't finda replacement casing for a reasonable price then the truck ends up in the scrap yard which really would be a shame
I don't know if you have a 720 kingcab/reg. cab longbox or a regular cab/short box, but either way, you need to find a transmission from a 720 that is the same length as yours and put your front case on it like suggested above, or just change the tail shaft housing over to your transmission, but you have to get the same length transmission, long shaft is 31 inches from the engine mounting surface to the end of the tail, or the short shaft is 26 inches measured the same way, all the 720 cases/gears are basically the same, but the cluster gear bearing will be bigger from 84ish on.
If you do change out the cases, but a new lower cluster gear bearing, it is the weak spot of these transmissions.
Don't buy a 4wd transmission unless it has a speedo drive gear, you need a speedo drive gear in a 2wd vehicle.
Posted: Thu Dec 05, 2013 1:59 am
Thing here is that the internals were apparently rebuilt rather recently on this tranny so if we keep it were gonna wanna keep its intrrnals. What other vehicles would the tailshaft joining likely work from? This is a cab with the rear seats and I'd say the box ain't real big but it's also not tijy.... I'd guess at a little under 5.5 or 6 feet for the length. Any idwas? Newest Nissan Tltrucks? Yay or nay
Posted: Thu Dec 05, 2013 2:17 am
Read through this thread and focus on the links provided by me and asavage.
The links provide the most transmission info you will find anywhere on datsun/nissan IMHO.
Come back and share your thoughts after you have had time to digest some of that information.