Differential gearing

[Tony Radford]

How big a job is it to change the rear end gear ratio? I think I'm geared a bit low. I have a wide ratio toploader and I tach 4,000 RPMs at 80 MPH. Does that sound right?

[pgermond]

Tony,

What ratio are your rear gears? I have 3:31's with a wide-ratio top-loader and I spin 2,900 rpm @ 70 mph (BFG 295's). As for changing the gear ratio on the rear-end - I believe that is no small undertaking.

[TurnpikeBoy]

It will be far, far easier - and probably cheaper - to get a TKO 600 transmission with either of the two different 5th. gear ratios. If memory serves me (improbable.... :( ), those are either .82 or .68 - the .82 gives you less rpm drop from 4th, but with the torque you likely have in that stroker the .68 will give you far better cruise rpm. I've got 4.09 gearing, and (in 5th gear) 75 mph is 2500 rpm; 80 mph is 2700 rpm with the .68.

Changing out rear gearing is difficult and experience-dependent; don't know what size tires you have, but going to taller tires will help some.

[bstandley1]

Tony,

If your interested, you can use the following link to calculate you rear end ratio in a round about way

www.368s.com/tools_rpm.php

Just plug in the numbers for a wide ratio toploader (2.78, 1.93, 1.32, and 1.00) and the estimated rear end ratio (about 3.77?)along with your tire size and you'll be good to go...

Bob

[Tony Radford]

I'm figuring "why stop now?" Engine rebuild, new carb, new polish, new ceramic coating on headers and side pipes, new wheel bearings, new tires, new driveshaft yoke and as of today, new transmission (rebuild).

[will butterworth]

you are going a long route---how is new engine performing? I was surprised at bottom end torque of this 351w with 383 stroker set-up.No bogging now--have to be aimed right.We re-worked side pipes as well ,ceramic, look good too. Will-alabama

[Tony Radford]

Hey Will, I'm not really sure on the motor as I only put about a quarter mile or so on it before I realized that my vibration problem was still alive and well. With all the work Lyle did and that new PC carb, I'm sure it's better than before. We were almost there with getting her back on the road when this transmission issue jumped out yesterday. When the J3 Racing folks attempted a test drive following all the other things they did, the car didn't have third or fourth gear. I was sure it was a shifter linkage issue, but when they pulled the tranny and opend her up, they found that the main shaft was broken in two. It looks like one of the shifter forks came off and fell down into the case. I'm supposed to get the trans back from Vintage Mustangs today and I'll carry it back to J3 for re-installation. Then I suppose I'll rob a local bank to pay for this latest round of invoices as my lotto sucess hasn't worked according to plan.

[Slither]

:eek:, sorry to hear of your trials, Tony. Hope it works out well for you.

[scott h]

if anyone actually has some first hand exp. onchanging gears i too would like to hear about it. changing gears vs. changing cam, pro and cons. it seems the majority of the labor would be disassembling the rear end. i assume the stub shafts have to be pulled to change gears. lots of tedious wrenching be no real technical skills involved. as a money/labor bill saving would it be best to just bring the center section to a skilled gear changer?

[RJacobsen]

Changing the ring and pinion is not a job for the inexperienced. There are to many settings that need to be correct or you will end up with a noisy rear end. You can no doubt save some money by removing the unit yourself but the ring and pinion setup should be done by someone with experience.

[Tony Radford]

Got the tranny back from Vintage yesterday. Completely rebuilt. Don said he's never seen a main shaft snapped off like mine was, and at the beefiest part of the shaft no less. Well, it will be back at J3 first thing this morning and with any luck, back in the car this afternoon. Hopefully, this marks the end of a long saga.

[Naumoff]

Good luck Tony.

I would call Butch Capp and see if he would take your center section on trade for a new one with the gear you want. It is worth a dime to find out if he would.

I am lucky. My brother knows how to set up rears.

[Tony Radford]

Finally, she's back from months of surgery, both internal and cosmetic. Very nice. I'm looking forward to doing a bit of cruising. I'll invest a few hours of detailing this weekend.