Tranny/Differential Strap help

[chachacourt]

Hey Guys,

I just can't get a break. There must be a zombie in this garage that does not want this car to see the street. I will not give up. Last week we decided to put some gas in the tank and fired it up and back it out of the garage. The gear went in but when I lifted the clutch, the car failed to move. It is the fork/pin in the tranny that failed to engage. Also there was no oil in the tranny. I wanted to hurt my mechanic so bad. We spent about four days taking the trannny out. Last night finally got the tranny back in place. Mech had forgotten to install the strap that goes over the diff before but reminded him that it must be install. We had some problem because the strap is on top of the two screws that are on top of the differential and the shaft. Why I am having problem getting it to sit on top of the diff behind those screws or the nech of the diff. I need it to go back approx 2 1/5 inch back but very hard and only sits on top of the two screws. I know that I am very wordy right now but its just frustration. My mech insist to leave the strap off and say that it wont hurt anything but I am a man that believe in if someone made it then it is for a reason and will not drive the car without it so help me out to see why it does not fit properly or if anyone ran into this problem.

[beermanpete]

If you are using the OEM type rubber mount you need the strap. The strap will keep the differential from moving too much if the mount shold fail.

If you have a solid (metal) mount you don't really need it.

[Zed Head]

I don't know the 240Zs but it seems to me that if you have the original R180 differential and all of the parts are installed correctly, the strap should drop right into place. Are you removing one of the big bolts, positioning the strap, then reinserting the collar and bolt?

Maybe a 240Z person knows but is it possible the mustache bar and diff mount are on backward and the diff is in the wrong place, moved back?

The strap actually has quite a bit of play in it when installed, it's more of an insurance piece to stop excess stretching of the rubber diff mount, or control diff movement when the rubber mount fails. You could drive the car without it, but I would be more concerned with why it doesn't fit. It should be easy.

[jmortensen]

DO use the strap, and DON'T use a metal mount. The strap is not a backup, it works with the stock mount. Metal mounts transfer lots of NVH into the chassis and if you drive hard you can tear the crossmember apart.

Another option, since this part of the car is trouble prone, is to get a Ron Tyler mount and never worry about it again. Search and you'll find info on that. Might be RT mount or R/T mount.

[chachacourt]

I don't know the 240Zs but it seems to me that if you have the original R180 differential and all of the parts are installed correctly, the strap should drop right into place. Are you removing one of the big bolts, positioning the strap, then reinserting the collar and bolt?

Maybe a 240Z person knows but is it possible the mustache bar and diff mount are on backward and the diff is in the wrong place, moved back?

The strap actually has quite a bit of play in it when installed, it's more of an insurance piece to stop excess stretching of the rubber diff mount, or control diff movement when the rubber mount fails. You could drive the car without it, but I would be more concerned with why it doesn't fit. It should be easy.

You maybe right!!! The problem that I am having is that my mechanic guy can't be told that something is mounted wrong. I know I am asking a lot but can someone with a 240z r180 innstalled send pics of diff/mustach,strap

[Carl Beck]

Maybe a 240Z person knows but is it possible the mustache bar and diff mount are on backward and the diff is in the wrong place, moved back?

Given the description of the problem - I'd say it is most likely the lower differential mount is on backward. We don't know if he took the mustache bar off at this point....

The strap actually has quite a bit of play in it when installed,

It has quite a bit of play when it's 30+ years old. It can be quite tight when using a new strap.

it's more of an insurance piece to stop excess stretching of the rubber diff mount, or control diff movement when the rubber mount fails.

The strap is there to prevent upward movement of the front of the differential. If the front of the differential moves up a bit too far - it breaks the rubber lose on the lower mount. The strap works with the lower mount -the lower mount prevents downward movement and side to side movement. You need both in OEM condition.

You could drive the car without it, but I would be more concerned with why it doesn't fit. It should be easy.

If I had to drive without the strap - I'd drive very easy until it could be replaced. Letting the nose of the differential move up/down will case other components to losen or wear.

A fairly easy alternative is to use in place of the OEM Strap - is the method that SCARAB used. A simple bracket that wraps around the bottom of the cross member - and connects to the top metal on the OEM differential mount - with rubber bumper between.

See: http://www.zhome.com/rnt/Scarab/ScarabTorqueControl.htm

FWIW,

Carl B.

[Zed Head]

I learned some new stuff. I've seen recommendations of getting a new mount to stop the "clunk" but don't recall seeing the same for the strap. Mine was so loose when I got my car that I assumed it was there for extreme movement or failure. I've never seen the Scarab mount either, though I have seen an L-shaped bracket designed to do the same, but with no credit given to Scarab (I assume that they never saw the Scarab mount either and came up with the L on their own).

chacha, there are some good pictures in the 1972 FSM, Rear Axle and Rear Suspension section, showing the differential from the bottom, sitting on the mount and cross member. If yours was misaligned, the front of your diff would not be visible in the same way it is in the pictures. 1970 might be different from 1972 though, since they moved the diff at some point for NVH purposes (as I understand things). If you have a 1970 FSM it might have similar pictures or diagrams.

[chachacourt]

the mustache bar is on. We had to take the shaft off and the tranny. prior to that the strap was off . upon returning the tranny; i insist that the strap should be on and now the strap is hard to stretch past the two bolt and sit at the neck of the diff.

[jmortensen]

Take off the front diff crossmember bolts that hold it to the frame. The front end of the diff will droop down, you can put the strap in and jack up the diff and put the bolts back in.

The factory strap/mount setup really is about the worst designed part of the car, that RT mount (or the Scarab clamshell modification that Carl posted) is a big improvement.

[chachacourt]

Hey Guys,

Happy More Z Years to all!!!!!!! . Well its been a long time since we talked. You guys are the best. You guys were right but remember I told you my mechanic guy is very self centered and a know it all. He does not take critics well and no one can tell him he does something wrong. First of all the car is home where it belong since early November 2011. I recently drove it to a friends home close to my home and he did a complete check to see if everything are placed correctly. As he mentioned two years ago to my mechanic, you guys mentioned it in July because we were having issue placing the strap. THE Mustache is on backward and the the diff mount backward. He had welded a piece of metal near one side of the bracket to place the strap but the strap is still on top of the diff four bolts. The car will be on jacks tomorrow and my friend and I will reverse what was done. Just wanted to let you guys know. Thanks. I have another issue though but will see you @ engine with tripple Mikunis thread. What do you think

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[Diseazd]

Chach.....My guess is the previous owner did a conversion on your diff. The early cars had the half shafts coming forward slightly to the diff. The fix was a slightly longer (later Z) driveshaft, a 72 or later hanger and a 72 or later mustache bar ( not straight like the early cars) and then you would reverse the diff mount or use a 71 or later mount (which moved the diff back a couple inches). All of this moved the diff back, made your half shafts come straight to the diff and got rid of a vibration found in early Z cars. However, when this was done , the diff strap now was 2 inches or so forward on the diff.....it was obstructed by the two bolts. It could be put on, but was stretched tight. Look at your mustache bar. If it isn't straight, you probably have a converted early Z.

[chachacourt]

We got everything back to where it should be. the mustache bar was backward, diff mount backward and a longer driveshaft. This is why my guy could not get the strap on the diff the proper way. After taking the car out of the shop, a friend of mine who has a 78 Z was able to work with me and worked things out. we changed bushings, placed the mustache, mount the correct way, we noticed the drive shaft was about 1 1/2 inch longer. We took it to a shop and had it cut and balanced. Ohhh, I found a nice used diff strap from zcarparts "Eric " Nice drivetrain thanks for all the help.