Take off with be good and highway will be good . I had 3.25 open and upgraded to a 3.50 posi on my 351w 4 speed. My rpm's were high on the freeway . Great take off tho. So i will go back to my 3.25. posi tho.

 

Should be good. Yes I have 3.55 (also got a good deal so couldn't pass it up) and wish I had went 3.4 which I think would be perfect.

 

I have 3.40's and I love them both freeway and streets. 3.25 you should be COMFORTABLE.

 

I love my 3.00's as well. IMHO you won't see THAT much of a difference going to 3.25's.

 

I just did this swap. 3.00 open, to 3.25 Eaton true track. Before the swap my 66 Ranchero could not really break the tires loose. Now, it is not a problem. I do wish I would have gone with 3.50 gears for better off the line response. The ranchero does way a lot more than a mustang though, about 1,000 pounds more. Yes, It was an improvement, but not as much as I had hoped for.
I know you didn't want to hear that. Sorry, but I thought I would give you an honest opinion.

 

I think you will be happy with the 3.25 with the 4 speed. I have 3.80 the last owner put in,I love the hole shot hate the highway. I am going the best of both worlds an stuffing a Tremec 5 in it. Then I will have a rebuilt toploader for sale.

 

Thank you everyone for the input. Next weekend I will do the install. If the weather here in Ohio is good? I will take her out for a drive and let you all know how the 3.25's feel.

 

Wife and I had to stop after an hour just to get out of the car.

hehehehe well I think you will find the 3.25s to be exactly what you are looking for then. It is a comfortable compromise.

 

I have 3.25 open at the moment and on highway I am pulling about 2600 rpm at 65 with a C4. I am going to 3.5 traction lock because of the C4, I have not got a AOD or T5 so pointless worrying about highway (don't do much highway miles any way) and will enjoy the around town cruising and hole shots.

 

It is an 8% difference. So look at you rpm at freeway speeds, say 2500 rpm. Now go to where the engine is spinning 8% faster, (2700 rpm in my example) and see if that is acceptable. Frankly 8% isn't a big change, so if you don't mind doing the work, I would swap it.

 

Im running 3.25 right now - love it. But.... I cant imagine too much of a change going from a 3.0 (yeah I know subjective)...but changing the pumpkin isnt too much of a hassle - If it were me - I'd change it out for the 3.25 also...let us know how you like it...

 

I run a T-5 with a 3.20 gear. When I swapped up to an 8" rear (after my 7.25" died), the donor axle came with a 2.80 gear. There was a huge difference between the two (which is why I went back to 3.20 gears).

Now I'm thinking of going up to a 3.55 (to get my cruising up into the power band in 5th gear).

If I find a 3rd member with the 3.55 gears already installed, is it just a matter of pulling the axles, then just swapping out the carrier? I'm further motivated, because we found a bit of play in the pinion casing when the 3.20 gears were installed.

Good luck with your swap!

 

It's all about ratios. I assume you have a wide ratio 4 speed. That would give you an SLR of 9.035 in 1st. Not bad but it won't be a barn burner. You basically want a ratio between 9 and 11 for decent take off and you have that. I have a t5 and 3.40. If I had it to do over again I'd change out the 3.35 1st gear for 2.95. 1st runs out a little quick for my liking and the 11.39 SLR makes tire spin on 1st almost inevitable. I'd prefer to be in the 10 range.

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I have a t5 and 3.40. If I had it to do over again I'd change out the 3.35 1st gear for 2.95. 1st runs out a little quick for my liking and the 11.39 SLR makes tire spin on 1st almost inevitable. I'd prefer to be in the 10 range.

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Im making this decision as this is being written about going 2.95 va 3.35 in a T5 with my 3.25 rear......

..... so would the 2.95 run longer but less tire spin or is that backwards (runs out quicker and more spin)?

Im looking for good take off yet nice highway performance (MPG)...

thanks - sorry for the hijack...

 

I am now wondering if I do indeed have a 3.00 in my car right now? It may be 2.79? I have to rev it up a lot to get it rolling. I counted tire rotations vs drive shaft and came up with 3 drive shaft turns for 1 tire rotation, thus my 3.00 rear. When I did his to the 3.25 rear end I came up with 3.5 turns. But when I counted ring and pinion gears 39 ring 12 pinion and divided it. I came up with 3.25.. I will only know for sure when I take the 3erd member out of my car.

 

Update!

irate:UPDATE!
Just pulled out the 3rd member in my car. 42 ring and 15 pinion. Math says that I have a 2.80 gear. Going to a 3.25 is going to be a big improvement.irate:

 

irate:UPDATE!
Just pulled out the 3rd member in my car. 42 ring and 15 pinion. Math says that I have a 2.80 gear. Going to a 3.25 is going to be a big improvement.irate:

I also swapped the 2.8 for a 3.25 tracloc and the difference was very nice. I also have a C4 with a 2200 Hughes stall converter.

 

Yep and 2.80s are common in automatic early cars.

 

Are you running a close or wide ratio 4 speed?..If its a close ratio toploader they are hard to get moving with a high rear end ratio like a 3.00..A t-5 trans or wide ratio toploader would also be good options to help get you underway better..

 

Close ratio toploader is a terrible trans for a street driven car.

Paul

 

I changed the 3.00 gears to 3.25 many years ago & it is very good. My mustang is a 1964 1/2 D code, 4 speed toploader.

 

2.80 to a 3.25 will be a nice improvement and is about the most gear I would run if you take the car on the highway much with the toploader. If you want more gear do the T5 swap.

I had a 65 coupe in the early 80's (highschool) and had a 351 Cleveland stuffed in it with a 4 speed toploader and 4.11 9 inch posi rearend..... that thing was buzzing 3200 at 55 on the highway which was the "maximum" speed limit then. It was fun around town but was terrible on the highway even for a hot rod teenager like me!

 

RE Update I Celebrated way to soon!

:crybaby: THe teat drive was BAD. Acceletion was fine. Once I lift off the gas the gears make so much noise! The gears are no good.
I want to buy new a new 3rd member and be done with it. It is just not in the budget.

 

If anyone with in a 5 hour drive of central Ohio has an 8 inch 3rd member, with an open 3.25 gear and you want to sell it. Please PM me.

Thanks.

 

The noise is only on coast? Did you check anything before you installed it?

 

I did not check anything. I dont know anything about rear ends to check. Maybe I even installed it wrong? I pulled the axles, then the 3rd member then put it back together with new 80-90 lube. Until I tried this swap I did not even know how to count the teeth to get the gearing. I took a shot on a used 3rd member. Becouse the 2.80 in my car that I was told was a 3.00 was so hard to get moving from a stop with my 4 speed. I made a mistake, now I want to learn from it!

I am hoping to pick up an other GOOD used 3.25 or maybe even a 3.00. It is just not in the budget to by new right now.

 

I ran a 3.25 Currie and thought it a nice upgrade with a C4. I later upgraded to a 3. 55 and my Rs at 70 were 3K (25.6 tires). It wasn't much fun. So, I swapped in a T5z and now, it's lots of fun!
Happy Trails....

 

My 66 still has the 2.8's. When I swapped in my WR Toploader I did have the money for 3.25's like I wanted but I kinda like the 2.8's. I'm not planning on changing them any time too soon. Yeah a little tall on take off but great on the highway. I can live with that.

 

Your 3rd member may be salvageable if the gears look good with either adjusting preloads at the least or new bearings at the most. Do some research on setting up gears, I don't care what your local shop tells you, there is no voodoo black magic for ring and pinions as long as you do your research and get the correct tools. The tools really aren't all that expensive either unless you go with super high end stuff. You probably just need to adjust something

 

I took my 3rd member to a guy to look at it yesterday. He noticed that the tabs that keep the u-joint centerd in the yoke going into the 3rd member were ground off. The only thing holding the drive saft centerd into place in the yoke was the u-bolts. He could not see any other problims with the gears or the bearings. He feels that puting the yoke from my 2.80 3rd member onto my 3.25 3rd member will solve my problim? He feels that if I did not get the u-joint centerd that that was the cause of my noise? I felt like I had it centerd? I hope he is right?