What is involved in changing the rear gears
 

What is involved in a gear swap with the ford 8.8? My car is #1867.....do I need to pull the complete diff and take it to a shop or are there other options?

Diff has to come out.
Gear change will require pinion depth and backlash be reset.
Might not be a bad idea to change bearings while in there.

Thank you for the response. I wasn't sure if there were any short cuts or special tools required. I would like to prevent taking any components out or loose if it is not necessary. I have asked around for recommendation on shops that can provide the gear swap service. I would like to have this done by a professional and I want to make sure I don't get the dreaded gear whine.

I'm interested in doing this also. Why are you swapping gear ratios?

Please post costs and follow ups.

I am on the fence about going to a stroked 385 big block and right now I just want to put a patch on my current 427 Windsor setup. It is a great motor don't get me wrong it just does not have enough power for me I have 3:31 gears now and was looking to bump it to a 3:73 as well as put in the cam Brent specified for me. I looked at going more aggressive with the gearing but I think the 3:73's are about as much as I am willing to sacrifice as I do a lot of 70mph + cruising. With a big block in the future the 3:31's might even be too much gear I'm really not sure......regardless it is just something I am looking at doing.

A big block with 3.31 gears will be great. If you go with 3.73 in a stroked big block your first gear is going to be useless for anything but ruining tires.
With that kind of torque you don't need different gears. You want to match up the gear set to typical driving speed and make sure the final gear puts the engine at a comfortable RPM. 3.31 gear with typical OD 5th will put you around 2100-2300 at 75 MPH depending on tire size.
Here's a link to a calculator that you can play with gear selection and tire size. RICHMOND Street Performance Calculator

I did it in my spf. Gears were hard to find since my diff was from Australia not sure what diff they use now. Took forever.

Current diff used is a ZF, same as found in the current Camaro and the ratios are available from GM parts. The previous diff was the BTR (from Australia as used in the last gen GTO) and gears are also available from GM.

The current Camaro offers the following ratios that I can find: 3.91/3.73/3.45/3.27/2.77 so a 3.31 does not look likely but the 3.37 would b close.

The 3:73 would be for my current setup until I did the big block swap in the future. I run 315/35/17's and would probably use a 3.31 with an OD 5th with a big block. My current setup turns 2700 at 70mph and that is annoying. The .64 5th would give me 2000rpm at 70mph and with the torque of a big block that would be a great cruising rpm

What trans do you have now? Feels like you might be doing this out of sequence.

As far as a gear swap, don't think that there are any shortcuts. Gear whine comes from setting lash and centering properly.

I have a TKO-600 with the .82 5th gear. Its a great street setup but my issues are below. I mentioned going to a big block in the future and that is what through people off. This gearing conversation is about the current 427W setup.

*Current cam peaks to high so its not a lot of action below 4K. It still doesn't have enough power up top for me.

*I thought going to a 3:73 would be something I could live with for the time being as an inexpensive way to add some performance. It would improve the car now and would improve If we get around to throwing in the other cam.

Ace do you know what spline axles you have?

Coach bought a .62 main shaft to swap in TKO 600 (.84) Cost about $160 for parts and $200 labor. We pulled the trannie and let a local Ford mechanic swap the shafts. He also does our rear end rebuilds and gear swaps.

Dwight
Florence, Al

Dwight,
I do not know what spline axles my car has. I can tell you that there is a greater than average chance that they are stock. Pardon for the ignorance but you will have to explain to me what the .62 main shaft swap does. This isn't the 5th gear option that is always discussed when talking about TKO-600's is it? I've heard that it is possible to swap the .82 for the .64 but that it requires the tranny to be pulled apart. Sounds like you guys have a good source for the tranny and gear modifications.

Ace,

There are two commonly used techniques for setting up ring and pinion gears. One is the appearance of the drive and coasting tooth contact patterns and the other is the Master Housing Depth or MHD method. Advocates of a particular approach have an almost a religious loyalty to their preferred method.

Each approach has its advocates and detractors. The tooth contact pattern approach usually will find as many opinions about shallow, deep, loose, tight as you have people to look at it. The problem comes from the subjective quality that visual appraisals of the tooth contact pattern before your eyes (or theirs) are subject to.

The MHD approach uses a Master Housing Depth dimension from the differential carrier bearing center to specific location on the pinion gear to set pinion depth. This dimension is the same for all rear ends in a given family i.e. Ford 8.8 inch, Ford 9 inch etc. Once you have pinion depth set you can easily zero in on your backlash dimension using shims on either side of the carrier to get you where you need to be.

The MHD approach requires no subjective visual evaluations everything is measures in thousandths of an inch. The drawback to the MHD approach is you need to be able to read a micrometer and you will end up making a few pieces of simple tooling to do the job. BTW, MHD is the way Ford sets up the rear ends before they leave the factory.

In the tooling department you will need a case spreader. and a 1" thick plate for measuring pinion depth (I provided a drawing below) along with a dial indicator and stand for measuring backlash. I have attached pics of case spreader and a drawing of the plate for you to duplicate. The case spreader can be bought from Rotunda for lots of money or fabricated from plate, bar stock, dowel pins and a turn buckle form McMaster-Carr for lots less money.

Case Spreader
http://www.clubcobra.com/photopost/d...4010-T7071.jpg

Pinion Depth Plate

http://www.clubcobra.com/photopost/d...epth_Plate.jpg

The third item I wanted to attach is an excellent write up on setting up rear ends using the MHD approach for Chrysler, GM and Ford rear ends by Randy's Ring & Pinion but the pdf file exceeds the site file size limits so instead I will provide you the url to down load it from.

Click here => Ring & Pinion MHD setup for the booklet. This used to be a nicely printed pdf but the visual quality appears to have deteriorated a bit in recent years. The important thing is the information is still correct and the pdf is downloadable.

Just in case you are one of the folks that embrace the reading of the tooth contact pattern method for setting up rear ends but don't know what to look for in terms of tooth contact patterns, here is the link to Dana's tooth pattern guide, click here => Dana Tooth Contact Pattern Guide

By far and without any doubt whatsoever, the absolute quietest, longest lasting rear ends I have had over the last 40 years were the ones I set up myself using the MHD method.



Ed

I would check with your engine builder regarding how well your big block will like 2,000 rpms. Depending on the cam, it may not like it at all. With a mild cam that may be k, but an aggressive cam is going to want a higher rpm to run right.

I actually prefer the .82 5th gear; and your 3:31 rear gear sounds like it would be a good match. The KC 427w should actually be a delightful set up. Maybe you should think about changing the cam.

What kind of horsepower and torque are you putting out? It would be helpful to have it dynoed so we can see you power curves.

What kind of power are you shooting for? I would think you can easily get 450-500 hp out of your current setup. I personally would not like to go to 3.73 from a 3.31 and 2700 rpm at 70 is closer to ideal than 2000 rpm. If you are driving long highway distances I can see you wanting to bring it down to 2200-2300 but not lower.

If you want to go to big block than go for it but you have a great setup currently imo.

Yes this was a TKO 600 5 th gear .82 to .64 swap. You have to take the trannie completely apart. Takes a couple of hours to do after you have the trannie sitting on the table.

Coach had a 428 / 461 KC 601 hp motor in his Hurricane. It would cruise at 2000 rpms. .64 5 th gear and 3.25 nine inch. Tires, not sure but I think 26" - 27" range.

Then he build a Unique with a 482 KC 620 Hp. Bought a .84 TKO but that is the one we changed to .64 after a year. Then it would cruise 1800-2000 range with easy.
Next car I have driven a lot is Lainhart's Unique with a '65 s.o. punched to 487 620 hp by Keith Craft. It has a 3550 with .68 O.D. 27" tires.
It will cruise at 2000 or less with easy.

It's all in the cam or mostly the cam.

My little 354 would cruise at 1300 rpms for miles with no jerking. We would laugh at it while we cruising down the back roads. I do have videos of it.


Dwight

I forgot, which TKO do you have?

The 600 has a 2.87 first gear. That is why I picked it over the 500. Much better 1st gear for street use.

Most of the guys are running 3.25 to 3.55 rear ends. The few with 302s and 351s that run 3.73 turn high rpms on the hiway.

Right now I'm driving a 408 KC that will cruise below 2,000. 3550 (.68) 3.55 26" tires

found this in my files

http://www.corral.net/tech/drivetrain/gears.html

Ed, thanks for all the information. I will take some time later tonight and review this. Sure didn't realize there was more than one way to setup a rear gear set.

If the big block is the direction that is decided this would be something that is discussed. Based on how many cubes you are running you may be able run a milder cam with such large displacement and still have more than enough power.
I enjoy everything about the 3:31 except for when I'm out on the interstate and I'm turning 2800rpm in 5th.

The dyno sheet from when Keith built the motor was peak HP 590 north of 6600rpm and TQ was in the 570's. I had the car tuned by Wayne Presley and a new QF750 mechanical secondary carb put on the car. To my own fault I had really gone through the car and it needed some care. The rev limiter was sat at 6000rpm, the fuel pump was some tiny little unit and the fuel lines were ridiculously small. After the car made less than stellar numbers I talked to Brent and we upgraded the fuel lines, fuel pump and changed the MSD chip to 7000rpm as well as changed the springs in the distributor......this really woke it up but still not enough for me.

The car on a mustang dyno was making peak TQ the wheels of 350 at 4500rpm and the HP was 360 at 6000rpm. These power figures were before I got it home and we made the above adjustments. I have a local dynojet that I can go through it on and I should probably do that to see where it is at now. Something also to consider is the car has 2" headers......so you have a huge set of headers, no rear gear and a higher rpm cam.

Brent said in his opinion the current cam was not ideal and had way too much split in the duration with too much overlap. I have another cam he specified just have not stuck it in yet......the gearing change was just a cheap way to pick up some acceleration but would make the 5th gear situation worse and I would have to accept that.

Dwight,
I have the .82 5th gear TKO-600

I think you need to address your power issues before you make a change to the rear gear. You're current set 3:31 and .82 5th gear is fine! Figure out why you wheel hp is just 360 when it should be closer to 500...

At the end of the day, the 3:31 to 3:73 swap really isn't gonna change your life very much; I think you're setting yourself up for disappointment when you should be focused on your cam/balancing out your engine set up.

And don't junk the 427w; it's (arguably) perfect for your car - just make it run better.