Given stock 302, 33" tires and 3.5 gears worth upgrading transmission?

[crutch]

I've been chipping away at projects on my first bronco resto and I've come to the point where I have to replace the clutch on my original 3 speed manual. Given that I have to drop the transmission and transfer case I started thinking about a possible upgrade on the transmission. Been researching all the threads and leaning towards AX15 or NV3550 given my driving habits (mostly city and highway).

I have a stock 302 which I will likely try and rebuild in a year or so with performance parts or possibly go with a 347 stroker.

I've read a number of the threads about engine, gear ratios, RPM's, tire sizes and if the system isn't designed to work together you get no value out of the OD. I'm very new to all of this so was looking for any advice on whether I should possibly do the trannsmission upgrade now or is it pointless unless I re-gear (which I want to avoid). Should I just do the clutch replace now and then maybe think about it once I do something with the motor down the road? My 3 speed isn't very smooth so this is part of why I was thinking about upgrading now.

Appreciate any recommendations.

Stock 302
3 speed manual
D20 transfer case
3.5 gears
33" tires

 

[DirtDonk]

Tough one. Sort of...
It's still a worthwhile upgrade for either of those, as you'll get a slightly lower first gear to start off from a standstill, which is already tough on a clutch with 3.50 gears and 33 inch tires.
Yes, with your current engine you'd be lucky to use overdrive going down hill. It might pull level ground at higher speeds if your engine is strong, but most would not.
Once it's been upgraded however, especially if you build a torquey 347 (especially if EFI), that can change. But what does not change is the fact that the gear ratios are completely out of synch with that tire size and an overdrive in an EB.
That same gear combo in a car? Much less of an issue. But pushing a brick through the air at 70mph at just 2000 rpm or whatever it ends up being, is just not in the happy spot for a stock EB engine.

Everybody's results may vary, but that's a pretty common thread hereabouts.
So it might still be worth the extra effort and money to do the work now, while you've got it apart. It won't be the happiest 5-speed around, but it might be a very cool 4-speed with an extra gear for after the engine work!

Paul

 

[DirtDonk]

Oh, I should add that the discussions of overdrive with 33's usually revolve around putting 4.11 to 4.56 gears in the diffs. With some using 4.88's if they wheel a lot.
But in my own experience, with 4.11's with 35's and a good running EFI engine, a Bronco can pull freeway speeds with just a little extra effort.
Not the same result with a stock engine.

So while you will always be at a disadvantage with that gear/tire combo, the engine can make a difference.
So can changing out to an automatic instead.

But the best result comes from a change of diff gears.

paul

 

[crutch]

So while you will always be at a disadvantage with that gear/tire combo, the engine can make a difference.
So can changing out to an automatic instead.

But the best result comes from a change of diff gears.

paul

Thanks Paul, what are the advantages of going with an automatic instead?

 

[DirtDonk]

Just more forgiving of too-tall a gear ratio with the tire size.
The torque multiplication and slip-ability of the torque converter helps you get off the line even with improper gearing.
It also means no more worn out clutches.

Well, except for the clutches inside the tranny, if you're a little hard on it.

Paul

 

[ChrisC74]

I've been chipping away at projects on my first bronco resto and I've come to the point where I have to replace the clutch on my original 3 speed manual. Given that I have to drop the transmission and transfer case I started thinking about a possible upgrade on the transmission. Been researching all the threads and leaning towards AX15 or NV3550 given my driving habits (mostly city and highway).

I have a stock 302 which I will likely try and rebuild in a year or so with performance parts or possibly go with a 347 stroker.

I've read a number of the threads about engine, gear ratios, RPM's, tire sizes and if the system isn't designed to work together you get no value out of the OD. I'm very new to all of this so was looking for any advice on whether I should possibly do the trannsmission upgrade now or is it pointless unless I re-gear (which I want to avoid). Should I just do the clutch replace now and then maybe think about it once I do something with the motor down the road? My 3 speed isn't very smooth so this is part of why I was thinking about upgrading now.

Appreciate any recommendations.

Stock 302
3 speed manual
D20 transfer case
3.5 gears
33" tires

I have a 97 stock explorer engine, 33s, 3.50 gears and a NV3550. The plan is to regear but for now it is a much more fun 4 speed to drive than the stock three speed was. I don't use the 5th gear at all yet but will someday after I put in my 4.33 gears.

 

[blubuckaroo]

Tdcrutch,
You might consider searching for a three speed tranny from a six cyl. Bronco. Those have a considerably lower first and second gear ratio, and so they work better with larger tires.

Bronco 3 spd (6 cyl) 3.41 1.86 1.00
Bronco 3 spd (8 cyl) 2.99 1.75 1.00

Lots of early Broncos were born as six cylinders and converted to V8. The ones I've driven just feel peppier than the V8 tranny.

Who knows, yours may be one of the six cylinder versions.

 

[trekgurl]

I got 302, NV3550, 235LT 85R/16, 4.56s

I freakn have so much fun it should be agin the law,,;D. That extra gear and the overdrive make it real nice in stop n go traffic and or cruising country roads. At 75mph it tacks about 2300 mph. I don't have big tires like the big boys but it's dialed in. That NV3550 is my second best mod.. the stereo being the first,, haha. You got love shifting them gears baby,,

49 degrees this morning,,,,top off and drove to work this morning,, It don't get no better

 

[crutch]

Thanks everyone. This helps explain why it is a little tough starting from a standstill with the larger 33" tires and 3.5 gears. I have bad clutch chatter and clutch seems worn out but its probably compounded by my setup.

I have been going back and forth on manual or auto. I want a manual but the traffic in southern California has gotten worse and I'll be cruising down to the beach so the auto might be more practical and worth researching a bit more.

Seems like 4R70W is highly recommended but a bit more costly. Since it's not going to see hard core off road use I wonder if the AOD is sufficient for my needs.

 

[bronconut73]

Thanks everyone. This helps explain why it is a little tough starting from a standstill with the larger 33" tires and 3.5 gears. I have bad clutch chatter and clutch seems worn out but its probably compounded by my setup.

I have been going back and forth on manual or auto. I want a manual but the traffic in southern California has gotten worse and I'll be cruising down to the beach so the auto might be more practical and worth researching a bit more.

Seems like 4R70W is highly recommended but a bit more costly. Since it's not going to see hard core off road use I wonder if the AOD is sufficient for my needs.

If you are going to go auto just go straight to the 4R70W. It is a great tranny. Lower first gear and overdrive
You will need a tranny controller like Bauman or US Shift unless you go oem fuel injection at the same time.

But don't go through the expense of an auto tranny swap without going all the way.

You will be glad you did.
You can re-gear later. Just keep it out of overdrive for now.

 

[needabronco]

I have an AOD with the 4r70W gearset (I believe) and I'm quite happy with it. Keep in mind if you swap in ANY overdrive transmission you will also need to change your gearing in your axles. My best advice there is 'don't fear the gear'! I originally planned on 4.56's and bumped to 4.88's and frankly wish I went straight to 5.13's! Yes it makes that much of a difference.

 

[OX1]

There is always the T-18/435. Some what clunky compared to modern trannies, but bulletproof, and way more gear in first than you could ever need. I have your same setup with engine/gears, and tires and 4th gear becomes sort of an overdrive. This setup works well if you are hitting the mountains a lot.

 

[needabronco]

You could always swap out your 9" ring and pinion to 4:11's and see how you like that? I'd even bet you could buy a used third member already set up with 4:11's fairly cheap.

 

[ugly74]

Itd be awful tempting and smart to throw a manual 5 speed in there now.
You can overcome the low RPMs at 70 mph, by driving 80-90 mph instead!

 

[broncnaz]

If you swap to a OD tranny then gears will be in your future. Dont fight it. Wouldnt hurt to swap now you just wont use OD. But on the same note waiting may be a better option you can shop for what you want and maybe even get a deal on it. Then you may be able to afford the gears at the same time. Meanwhile throw in a new clutch and drive it for awhile. Many of us have driven that combo for years with little issue other than less clutch life.

 

[Broncobowsher]

Thanks everyone. This helps explain why it is a little tough starting from a standstill with the larger 33" tires and 3.5 gears. I have bad clutch chatter and clutch seems worn out but its probably compounded by my setup.

I have been going back and forth on manual or auto. I want a manual but the traffic in southern California has gotten worse and I'll be cruising down to the beach so the auto might be more practical and worth researching a bit more.

Seems like 4R70W is highly recommended but a bit more costly. Since it's not going to see hard core off road use I wonder if the AOD is sufficient for my needs.

As stated above, got straight to the 4R70W if going that route. There are a lot of happy owners out there. AOD conversions are a lot more hit and miss at being happy. Some have even pulled them out not liking them. Never heard of a 4R70W being pulled out from being unhappy with it.

Also, don't fear the gear. Hard to imagine saying this, but 4.88s make good highway gears. That was with 33" tires.

Don't look one step at a time. Plan your build and work the plan. You need axle gearing. How much? Depends on the transmission that you eventually plan to use.

Non-overdrive transmission, small block V8, 33" tire; 4.11 gear has proven to be about as ideal as possible time and time again.

 

[crutch]

Thanks everyone for the info, already learned a ton. The 4r70w is mighty tempting. Some of the threads look a bit ambitious on all the customization to get it to fit. I'll search the forum a bit more.

 

[ntsqd]

'Bowsher said what I was going to say, make a goal for where you want to be and buy the parts that keep you moving in that direction. Lateral parts purchases are just wasted money.

Sounds like you need to decide on Auto or Manual first, then pick the trans you think that works best for how you want to use your Bronco.

As to AOD's, I had one in a street car with a 302. I thought it's OD ratio was too tall. The drop in RPM's between Drive and OD was too great and the engine would fall out of its powerband. I usually held it back in Drive until going at least 70. Not sure how that might translate into a truck with truck gearing and tire sizes, but I can say that I've also had a 700R4 in a truck (with a 350) and I thought it's OD ratio was much better - less RPM drop so the engine didn't fall out of it's powerband like it did with the AOD. Were I going auto in my Bronco it would be a 700R4.

 

[crutch]

Don't look one step at a time. Plan your build and work the plan. You need axle gearing. How much? Depends on the transmission that you eventually plan to use.

Couldn't agree more. This has been the first mechanic work I have done on a car or a Bronco so it's been a learning process typically one step forward two steps back but at least i'm having a Blast!!! Lets just say the second bronco I build will be dialed in.

You guys have inspired me to do it right and go with the auto now, I think I will be happier in the long run. Going to put together a parts list for the 4r70w and come up with a game plan. More question to come I'm sure...