please help

[hopper]

Ive searched and searched and cannot find a specific answer. hope somebody here can help. I drive a 1978 Datsun 620. it has the z22 engine and 5 speed trans from a 1981 720. my 620 still has the original rear end. in 5th gear at 65mph im turning 32oo rpms. so here are my two questions: will a rear end from a 1984 2wd 720 be too wide to fit under my 620?, and will a 5speed trans from a 1984 2wd z24 720 bolt to my z22 engine? thanks for any and all help. and if wondering, I am swapping trans bc mine is losing reverse and whines pretty bad. the rear end swap is for better gearing to drop the rpms at highway speed. thanks again

[Jayden71]

Instaed of changing out the whole rearend just swap out the 3rd member for something a little longer legged.

 

z24 wil bolt to the z22. I'm sure Datsunmike will chime in here soon

[hopper]

and which clutch should I use? z22 or z24? what vehicle would I find a longer 3rd member? thanks

[Jayden71]

720s had all kinds of different ratios. I do believe there is a tag on the door jam that says what they had. The '79 620 had 411s. Your clutch would probly be the same Z22 and Z24

[hopper]

awesome thanks. im going to try and use the 3rd member out of the same 720, and its door jamb vin plate doesn't identify what its rear end has. thanks again

[datzenmike]

For info on what rear end and ratio is in the 720, simply look under the pass side hood hinge on the inner fender. There is an aluminum engine tag there that says what the factory installed when built. Axle info is the far right HF38 means 3.889 a 41 would be 4.11 a 35 would be 3.545 and so on. 

 

Your '620 will not have that info but a '78 manual or automatic will have a 4.375 axle.

 

To remove the 3rd member, remove the rear brake lines and possibly the emergency brake cables at the backing plate. The E brake cables may stretch enough. Loosen and remove the 4 X 17mm axle bolts behind the backing plates and pull the axle outwards from the differential to disengage the side gear splines. Mark and remove the driveshaft so it can be returned to it's original position. Drain the differential and inspect the bung. It has a magnet on it to collect metal. Clean it so you can compare it on the next oil change in 30K. Remove the 10 x 12mm bolts around the 3rd member and remove. Have a care as it weighs about 60 pounds or more.

 

Clean the mating surface and use a good quality gasket sealer like Permatex. The one I used was blueish like toothpaste gel and very thick and not at all like cheap RTV, let set for 10 min and join the parts. Reassemble and fill with half US quart of GL-5 80w90 gear oil.

 

Yes the '85s five speed will bolt to your Z22 as long as the length is the same. Either 31.5 or 26" long. But first I would check and probably fill my transmission oil. Use GL-4 (not GL-5) 90w gear oil. Noise is often lack of maintainance and needs oil.

[hopper]

thanks. the trans has new lucas gear oil. its getting harder and harder to get into reverse and is just worn out. im getting a complete 720 donor truck. so I will just swap trans and install a new clutch and be done with it. do you know if the 720 3rd member will bolt into my 620 housing? thanks for yalls help. I believe the 720 is missing the underhood id tag. ill double check, but is there another way to find the ratio? thanks again

[datzenmike]

its getting harder and harder to get into reverse and is just worn out

Grinding??? Check the clutch master has fluid in it. Likely low and air is no in the system. Fill and bleed it and you're back in action. Way cheaper than tranny swapping.

[hopper]

no it doesn't grind. it acts like it is still in neutral when I shift into the reverse position. the only codes I could find on the 720 was on the door jamb plate. trans code fs5w71b, and rear end h190m. the truck was manufactured in 1983 also. thanks again

[Farmer]

Farmer Joe just did a swap on his rear end. He use the third member from a 720 running a z24. Check out his thread in the truck section.

[hopper]

thanks, but I cant find the post

[datzenmike]

no it doesn't grind. it acts like it is still in neutral when I shift into the reverse position. the only codes I could find on the 720 was on the door jamb plate. trans code fs5w71b, and rear end h190m. the truck was manufactured in 1983 also. thanks again

.

The door jam only had a build date. Look on the passenger side inner fender just below the hood hinge. There is a credit card sized aluminum tag with the ratio on it.

[datzenmike]

thanks, but I cant find the post

 

thanks, but I cant find the post

Use Search function under the 510 top right of this page. Type Farmer Joe, google search... Farmer Joe profile comes up, hit FIND CONTENT and his topics come up. About 7 topics down is something about a king cab. Jump to the last page... post 424. Looks like a rear end swap. With practice you can find this in about 15 seconds.

[hopper]

thanks again for the help. ill try to get some pictures up soon