Building a 56 Chev wagon for a guy, it has what he says is a 700r4 from a Vette. No age known, but it has a vehicle speed sensor in it as opposed to speedo cable. am wondering if there is a slightly longer tail shaft for this trans (4 bolt tail shaft housing) so i can use not only a regular speedo cable, but won't have to lengthen a drive shaft for it? This one also appears to have been modified, as I can't figure out the type of mount it's supposed to take... weird.
Change the tail shaft housing means changing the tail shaft also. Complete tear down to do that. You can get the speedo parts from chevrolet. Looks to me to be simpler to make a longer drive shaft. Jus me sayin As far as the mount a picture is worth a thousand words.
You can not change the tail-shaft to make the ****** longer. All 2 wheel drive 700R4's measure 30-3/4" in total length. All 700R4's can run either a speed sensor or converted to run a typical speedo cable. It is important to count the input shaft splines. You want a 30 spline input shaft. The alternative is a 27 spline input shaft and they can basically "explode on impact"! Meaning a 27 spline 700R4 is junk, stay away from it. Another thing to look at is the case, more importantly the markings on the bellhousing. There are 3 types of cases. There is a case with no markings, an "MD8" case and the "K" case. You want at least an MD8 case, the K case is the strongest 700R4 case and the case with NO markings on it is garbage. These marking (if any) are found casted into the bellhousing on the right (p***enger) side of the bellhousing. Also the ****** mount to ****** bolts are metric as is ALL the hardware on a 700R4.
Thanks folks I'll look next time it's in the air. I will probably change the housing regardless due to the mount issue. ,, duh.. never occured to me about the shaft lol! I don't do a lot of trans work
I just changed the tail shaft extension housing on my '90 Corvette 700R that is going into my '46 Olds project. I used an '86 ish Camaro extension housing (Impala SS is similar from memory) that allows a mechanical speedo drive. You also need to change the transmission output shaft as well because the Corvette extension housing is slightly longer than others and the tail shaft rides up in the housing rear bushing and won't provide sufficient support for the yoke. Also the Corvette case has no provision for a rear transmission mount as the differential cradle bolts on, the new extension housing is where the mount now is. There are no bosses on my Corvette case for a transmission mount.
I've seen 700R4 cases with provisions for three mounts - two positions under the trans tail, and the rebuilt core in the diesel Suburban I parted out a few years ago had a mount that bolted to the sides of the tail housing with a metal bracket that actually put the mount bolt just behind the end of the case, and below, made it a pain in the *** pulling the trans out over the truck crossmember. So maybe the tail from a truck trans will be helpful. What year they go to electronic varies, 88-up on the pickups, but the Suburban is mechanical at least through '89 if not '90, and I presume same for vans.
I have a 1993 Corvette transmission, with the unique tailshaft housing, but there is a pad on the main body that takes a normal mount.
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