Question on going from 2.73 to 3.55

Topic: Question on going from 2.73 to 3.55 (Read 6666 times) previous topic - next topic

Question on going from 2.73 to 3.55

Reply #15 – October 08, 2012, 07:40:12 PM

Quote from: 86cougar;400071

Sounds like 3.73 rear gears w/351 Cleveland, AOD transmission might be a good set up for me. Who knows, I might go with a 5 speed.

That would be killer!

Question on going from 2.73 to 3.55

Reply #16 – October 08, 2012, 09:00:01 PM

3.73 on the left and 2.73 on the right. I exclusively use ford gears on all my 8.8 builds. They are easy to set up and they are QUIET. Good luck

A crush sleeve eliminator is mandatory.

Everything has to be CLEAN and a good quality TORQUE WRENCH IS MANDATORY!!

And you need dozens of shims to set it up correctly

And all bearings AND RACES MUST BE REPLACED!!

A special torque wrench is needed to set up the pinion pre-load

Just posting for discussion on the change over!!

Question on going from 2.73 to 3.55

Reply #17 – October 09, 2012, 03:42:22 AM

good pictures Tom! Good incite on this procedure, I am pondering changing gearsets in the future.

Question on going from 2.73 to 3.55

Reply #18 – October 09, 2012, 05:50:51 AM

Thank YOU

Proper way to remove ring GEAR

Remove the bolts and use a flat punch with the HOG IN A VICE. use a heavy towel to not mess the gear up if you plan on REUSING IT!!!

Installing the ring gear is best dun with pulling it on. Here is a ring gear from my TYPHOON being installed with long bolts backed up with nuts. I thread the bolts in the ring gear all the way and use the installed back up nuts to pull the gear on the HOG. Some final drives have left handed threads so make sure when you remove the bolts you are in fact not tightening them!!! Then install the proper bolts with RED LOCK TITE and torque properly in a 180* pattern. Also make sure the ring gear and hog are free from nicks debree and gouges. Any dirt or material that winds up in between them will make the gear not sit flat together. And do not use oil or lubricants. It will fill the blind holes and you can break the bolts with HYDRAULIC LOCK UP.

Question on going from 2.73 to 3.55

Reply #19 – October 09, 2012, 06:10:23 AM

Also always use FACTORY BEARINGS AND SEALS!!!!

Here is a bearing from an axle that the customer bought a rebuild kit from the aftermarket. Note the lack of roller bearings compared to the factory one. I never use aftermarket or store bought bearings and seals. Other than GENUINE TIMKEN. Note the difference in the bearings and the number of rollers.

Also always pack the back side of the pinion seal or any seal for that matter. It prevents the GARTER SPRING FROM POPPING OFF WHEN YOU TAP IT IN. Ask me how i know this. The grease holds the spring in place nicely. I think i INVENTED THIS!!!

Also make sure you have the proper tools to install the races and seals. Never install a seal without the proper driver. Tapping around a seal with a hammer is a NO NO. Us the proper tools

Question on going from 2.73 to 3.55

Reply #20 – October 09, 2012, 06:54:21 AM

Good pic set. They taught us in school to pack the back of the seals with transgel, but I've seen lots of guys use vaseline for that.

Question on going from 2.73 to 3.55

Reply #21 – October 09, 2012, 09:46:18 AM

Like I said, I always learn a lot from this forum. Thanks, for the pictures! I have only watched a friend work on the differential on my jeep, I've never done one yet.

Question on going from 2.73 to 3.55

Reply #22 – October 09, 2012, 10:24:30 AM

Nice pics Tom, I was taught by a friend out in Chehalis Wa how to rebuild diffs. He did the vasiline trick as well. Like you, he was extremely buttstuff about cleanliness, proper tools, and proceedure. That rubbed off :D

Question on going from 2.73 to 3.55

Reply #23 – October 09, 2012, 12:10:37 PM

Tom, this subject would make a terrific in-depth tutorial to share your vast knowledge. Thank you for the pics, could you post more about the proper setup, tools, etc? Perhaps even recommendations as to where one might obtain the necessary tools and consumables like shims, dial indicator, seal installation tools, etc.

Thanks!

Question on going from 2.73 to 3.55

Reply #24 – October 09, 2012, 12:59:41 PM

Sure RANDYS RING AND PINION has tech support as well as tools and shims. You can access the web site by typing ringpinion .com. I probably set up more gears than most. Been doing it for many years. One thing you must understand is the 8.8 is a final drive that cant be spread. Case spreaders are a must on big axles but the 8.8 does not have the provisions. I made a home made one and it does not really work that good. The carrier shims must be selected and tapped in so it is a little more involved. Normally i do not use vasoline for garter retaining as it is to thin and does not hold as good as heavier grease. I actually have a 5 LB can of long fiber grease to hold cluster gear bearings and seal garter issues. Personally i think Vasoline is to thin but what the HECK!!! Thanks and i am glad you like the write up.

Question on going from 2.73 to 3.55

Reply #25 – October 10, 2012, 04:36:40 AM

I have just one thing to add. If you do a lot of freeway, I think the 2.73 gear is perfect for a commuter car. Around town, I think 3.55's or 3:73's are better.

The overall drop in economy is probably close to loosing your overdriver gear, at freeway speeds.

Drive around in "d" instead of od if your thinking about a gear swap.

My wagon with 3.55's shifts first at 35, second 55-60ish, and not sure on third, probably over 80mph.

The birds/cats I've had with 2.73's shifted at 42, second at 65-70, and again, not so sure on 3rd, for wot automatic shifts.

In a 75mph zone, the wagon requires a bit more throttle, and I would guess 600-800rpm's higher engine speed. My bird, if I drove 62mph over a 50 mile freeway commute, I would average 30mpg or higher. If I did 77mph(highway was 75mph, 77 was where the car liked to sit), mileage dropped to 25-27ish. If I did 75mph in drive(simulating 3.73 gears), I averaged 22mpg, which is what I get out of my wagon with 3.55's.

I hated doing less then 75mph though, because I would constantly get passed and have cars ride my rear end. 62mph was a good speed because then I could just cruise with the big rigs, and pass them on the uphills and overpasses.

Question on going from 2.73 to 3.55

Reply #26 – October 10, 2012, 05:55:40 AM

First thing is shift points are determined by line pressure and throttle opening. When line pressure equals throttle pressure the tranny shifts!!!

With that here is the tables on MPH @ RPM With a 28" Tire and a .68 OD!!!

2.73 @ 80 MPH 1782 RPM

3.55 @ 80 MPH 2317 RPM

3.73 @ 80 MPH 2435 RPM

Drive around in "d" instead of od if your thinking about a gear swap. NOPE!!!!

In drive the transmission would not lock out the converter adding another 300-350 RPM to your thinking!!!

So going to a 3.73 would increase mileage overall other then on the highway that is a given. But the overall fuel usage would be comparable

Engineers are designing transmissions with more gears to get better mileage. But with the parameters of the transmissions you are talking about just dont make it. So either stay with 2.73 which in my opinion are ATROCIOUS for overall performance and loss of acceleration and overall performance. Or change out to a 3.73 and bring that engine in to it's peak performance RPM BAND. YOUR CHOICE!!!

Using drive instead of OD 28" tire

@80 MPH 3.55 3708 RPM

@80 MPH 2.73 2921 RPM

this is one to one no lock up!!!

Question on going from 2.73 to 3.55

Reply #27 – October 10, 2012, 07:28:57 AM

In the AOD the direct clutch engages solidly to the torque converter housing (lockup) so whenever you shift into 3rd the connection to the motor is solid. And since 4th is just the further application of the OD band, 4th is a solid connection as well. With my setup, my WOT upshifts are about 6200 rpm or so. Before the gear change and the trans work my WOT upshifts would come around 5000 rpm.
My car has 3.73 and a .7 overdrive (a result of the wide-ratio mod), and I've got about 3000 rpm at 80 in 4th. I've got the full digital cluster, so that's as precise as I can get.

Question on going from 2.73 to 3.55

Reply #28 – October 10, 2012, 12:25:51 PM

According to B&M the converter they sell eliminated LOCK UP. I am not an auto guy by any means but releasing lock up is accomplished how in an AOD. Once again i am not an auto guy but their must be a way for lockup to disengage when applying the brakes. Please advise as once again i do not excel in auto transmissions. 6 speeders is my thing. With a 6 speeder i can run gears as tall as 4.88 on the street if desired. Just saying!!

Note driving an AOD as i remember had a distinct lock up. But it has been a very ling time since i have driven one. I will take you word for it FOE. Either way a set of 2.73 gears are best used as an anchor for a DINGY.

Question on going from 2.73 to 3.55

Reply #29 – October 10, 2012, 12:39:34 PM

A shop I worked at years ago had a horseshoes pit in the back they made with a pinion gear welded to a pipe and driven into the ground. The owner said he used the ring gears because in his book close was good enough for hand grenades, but didn't buy into the idea that close was good enough for horseshoes.

As far as the AOD goes, they can't lock in 1st and 2nd, and you're not likely to stop in 3rd or 4th. once you put your foot on the brake and start slowing, you downshift to an unlocked gear before even getting close to stopping. AOD, AODe and 4r70 are the only trans I ever heard of that are like this, anything else has an electro-hydraulic lockup clutch.

I'd love to have the cash to have a 6M, or even a 6A, I'd even like to have the money for a 5M swap. Unfortunately I'm stuck with a column shifted slushbox. All I can do is make what I have work as well for me as it can.