Hello all, i recently did the S5 13bt, engine and gearbox conversion, in my S3 85 rx7. When mounting the S5 turbo gearbox i felt like it was sitting alittle to high in the tunel. I used the original S5 gearbox mount and rubber V mounts. Had to adjust the 4 bolt up holes so i could bolt to under carage. All seemed to run ok, no bumping or grinding on stock suspension. I have since lowed the car about 1.5 inchs in the front and 2 inchs in the rear. Im now experancing "Tailshaft Grind" under full load or hitting bumps. Just wondering what would be the best way to over come this problem. Maybe a better gear box mount option to lower it in the tunel abit more??? Please share ur thoughts on this problem or post pics of ur S5 gearbox mounting setup in S3. I will try to post up pics of the setup soon... Thank all

 

2 items to check, driveshaft centerline alignment and free travel of the shaft at the tranny. The driveshaft should not have a centerline that lines up through the tranny, shaft and diff and the travel should have have at least 1/4" left under full rear suspension compression. U-joints are designed to have a slight offset of centerline for rotation. If they line up, the driveshft will tend to vibrate more. Since you probably had the shaft cutom made, it may be a tad long now that the suspension has been lowered.

 

Hi Trochid, thanks for ur feedback. Good info, I will definetly check it out, there is a slight vibration only when cruising at about 100kmph. Im running a 3" custom shaft, balanced and measured by engineer to fit for lowering. The bump and grind that im refering too, is from the tailshaft hitting and grinding itself against a small lug/pully for the handbrake cable, located in the tunnel. I think I've probably mounted the gearbox to high or incorrectly and thats the reason why the tailshaft is grinding in the tunnel. Im a first timer for this coversion. Not sure if i have mounted the S5 gearbox correctly, by using the S5 rubber V mounts. If anyone knows why my tailshaft would be grinding in the tunnel or how I could prevent this, please let me know. Thanks again :-)

 

I agree with your assesment, tranny's probably mounted too high. If you could take a pic of the rear mount, that might help. Your's is the first one I've run across that rubs in the tunnel, but then the Aussies tend to lower more than the States guys, usually with King springs too.

 

Yes ur correct, im running Kings superlow in the rear, Kings low in front and KYB shox alround. I will try and put some pics up soon.

 

Yes ur correct, im running Kings superlow in the rear, Kings low in front and KYB shox alround. I will try and put some pics up soon.

 

Yes ur correct, im running Kings superlow in the rear, Kings low in front and KYB shox alround. I will be puting some pics of the gearbox mount, alinement and hole car pics so u can see how shes sitting, posting up soon.

 

Sorry about the tripple reply it been happening to me abit lately. Admin please delete.

 

Hello all, i recently did the S5 13bt, engine and gearbox conversion, in my S3 85 rx7. When mounting the S5 turbo gearbox i felt like it was sitting alittle to high in the tunel. I used the original S5 gearbox mount and rubber V mounts. Had to adjust the 4 bolt up holes so i could bolt to under carage. All seemed to run ok, no bumping or grinding on stock suspension. I have since lowed the car about 1.5 inchs in the front and 2 inchs in the rear. Im now experancing "Tailshaft Grind" under full load or hitting bumps. Just wondering what would be the best way to over come this problem. Maybe a better gear box mount option to lower it in the tunel abit more??? Please share ur thoughts on this problem or post pics of ur S5 gearbox mounting setup in S3. I will try to post up pics of the setup soon... Thanks all

 

Simplest thing I can think of is to get longer cradle/crossmember bolts and shim the cradle down with washers. Shouldn't need much looking at the scratch on the driveshaft. Other option would be to see if the splayed U that mounts between the tranny and cradle/crossmember can be shifted down into the cradle more.

 

I have tried moving the box lower into the v mount, but the v taper wont alow it to move. With using shims, im thinking this might be deemed unsafe when trying to pass road worthy inspecting. So it needs to look stocko. What is the tipical way that most people mount the S5 gearbox. ie. What mounts are used.

 

I've tried moving the box lower into the v mount, but the v taper wont alow it to move. With using shims, im thinking this might be deemed unsafe when trying to pass road worthy inspecting. So it needs to look stocko. What is the tipical way that most people mount the S5 gearbox. ie. What mounts are used.

 

Once again sorry about the double reply, not sure why its happening. Admin please delet.

 

Ended up using 10mm shims to drop gearbox crossmember down, works good, no more grinding. Thanks again Trochid for the good info.

 

Here is what I did.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/13b-rew-write-up-764389/

 

Happy to help and glad it worked out for you.