anybody ever completed an rear axle swop?

[bisonfan]

Has anyone ever completed a rear axle swop on a pickup before? Appears pretty easy but...

The truck I am considering switching out the rear end on is a 1994 Dodge Ram 1500. The motor is the 3.9L V6 with a 5 speed manual. The transmission ratios are as follows:
1 2 3 4 5 R
4.02 2.32 1.40 1.00 0.73 3.55

The rear differental is 3.21.

Most would say buy a more powerful truck but this truck works good for running around and occassional light pulling (and it is paid for). The truck has 98,xxx miles on it so it is far from shot.

The reason I would like to change it out is that it is a doggy thing, plain and simple and could benefit from a better gearing ratio overall, not just for towing. (can't pull it's own weight in fifth gear againist a small wind)

I spoke to a dodge Dealer about a swop, they suggested a 3.90 rear end to give it more power. Per this http://www.4lo.com/calc/geartable.htm (wheel diamter is 28.5") a 3.90 rear would do ok, a bit on the power side. However a 3.55 appears to be a good balance but may not realize as much as I would like. 3.55 &3.90 were the OEM axles, so it would easy to do a swop theoritically.

If anybody has done this, what were your results? was it worth the change out?

Did you change the gears or is the axle route better? Just generally looking for some feedback on the idea...

 

[ph98223]

Re: anybody ever completed an rear axle swop?

You should go to www.dodgeforums.com they have a section for your gen. of ram and ask them questions you probably will get some good advice from the people there. Not that you wont get good advice here. but it doesnt hurt to look around

 

[dutchdog]

Re: anybody ever completed an rear axle swop?

Its a lot easier to swap the whole axle. 4 u-bolts, brake lines, and e-brake. takes about 2 hours with air tools. The 391 gear will give you a ton of pulling power but hurt your hiway milage. 355 will give you some pulling power but not hurt as bad at the pump. It depends on what you plan on doing the most. I put a 391 in a dodge pickup hot rod with a 727 3 speed auto. It would top out at 110 mph but it didn't take it long to get there. Since you have the 5 speed standard, I would go 391 if most of my driving was in town. 355 if more was hiway. Hope this helps.

 

[bisonfan]

Re: anybody ever completed an rear axle swop?

Thanks for the responses. I did post over at dodgeforum.com last night as well about the same question. Have recieved a few responses from some very knowledgable individuals.

We are looking for more power in general but the truck is more of a run around truck then a pulling truck. (We have a 7.3L PSD F350 for that.)

I am leaning towards the 3.55 gear set as the guys over at dodge forum thought that the 3.90 was probably too low as well.

 

[windsors03cobra]

Re: anybody ever completed an rear axle swop?

Going from a 3.2 to a 3.5 is going to be mostly unoticeable, the truck will still be doggy and you will have wasted your time and money.
You have overdrive, I would go 4.11 or 3.90 or go home.

Good luck

 

[109jb]

Re: anybody ever completed an rear axle swop?

I'd go with the 3.90 personally. Is this a 4 wheel drive or a 2 wheel drive. A 4 wheel drive you are also looking at a change in the front axle too. For now I'll assume it is a 2 wheel drive. It is much easier to just swap out complete axles rather than switching the gears in your existing axle. You might want to check around at the cost of having someone else put the gears in. I had a shop do that several years ago and I don't recall it costing a ton of money.

 

[Sixmark]

Re: anybody ever completed an rear axle swop?

Did anyone bother to mention that you can change your final drive ratio just by changing tire sizes , if you want a good idea of what your truck would pull like with some 3.50's instead of 3.20's just slap a set of smaller tires on it.

This will help you get an idea if you are going to have to use the 3.90's

 

[Yellow Yota]

Re: anybody ever completed an rear axle swop?

Much easier to swap complete housings than it is to change a ring and pinion. Especially if you don't have any specialized tools. I would certainly check with a couple of shops to see if it would be cost effective to have them just do a R/P swap unless you already have a donor complete axle. Probably under $200 for a set of gears, plus setup. I'd recommend either Yukon or Richmond gears. I've had problems with other brands not setting up well or failing early.
As far as ratio, I had a '99 Ram with the 5.2 and 3.55's with an auto tranny. With stock tires it sucked. It would drop out of OD just going over an overpass on the freeway. With no load in the truck.
I'd go with the 3.90 or 4.10 from an "offroad" packaged truck if possible. Especially if you tow anything.

 

[smokeonthewater]

Re: anybody ever completed an rear axle swop?

Well first off swapping gears WON'T give you ANY more power... instead it will just lower your gears..... The only real benefit in acceleration will be in first gear. After first gear you can get the same effect as a regear from just downshifting... For example if you have a hill that you climb now at full throttle in 3rd gear at 50 mph.... you could regear and end up climbing the same hill at full throttle in 4th gear at 50 mph.... If you currently do ok in first gear then just stop using 5th.... If you are having a hard time starting from a stop then I would consider a swap....

That said 4:10 manual and 4 cyls generally go well together and I have a 4.0 inline 6 cyl in a jeep with 4:10's and 31's and it is decent but uses alot more gas than it did with the 3.08's that were in it before and I doubt your tires are more the 29" tall

I'm thinking that 3.73 would likely be a good choice for you

 

[bisonfan]

Re: anybody ever completed an rear axle swop?

Well first off swapping gears WON'T give you ANY more power... instead it will just lower your gears..... The only real benefit in acceleration will be in first gear. After first gear you can get the same effect as a regear from just downshifting... For example if you have a hill that you climb now at full throttle in 3rd gear at 50 mph.... you could regear and end up climbing the same hill at full throttle in 4th gear at 50 mph.... If you currently do ok in first gear then just stop using 5th.... If you are having a hard time starting from a stop then I would consider a swap....

That said 4:10 manual and 4 cyls generally go well together and I have a 4.0 inline 6 cyl in a jeep with 4:10's and 31's and it is decent but uses alot more gas than it did with the 3.08's that were in it before and I doubt your tires are more the 29" tall

I'm thinking that 3.73 would likely be a good choice for you

The truck is 2wd with 225/75R16 tires. Right now 4th is the top gear, fifth gear is pretty much useless... The truck is owned by dad. He drives it work roughly 10 miles one way. His work requires him to occassionally haul small loads 1000 lbs or so I would say. A few years ago he pulled a ultra light camper with it (19' I believe). It did less than ok but didn't get much over 55mph with it. He bought a used F350 with a 7.3L power stroke in it. He has since upgraded campers He does pull other trailers with the "little" truck but they are 2000 lbs or less otherwise he just uses the Ford.

Starting out is ok by itself but you do have to give it a bit more gas then other manual tranny's. With a load you almost have to "slip it" a bit to get it rolling...

I currently have the truck at my house and am pulling his boat with it. The boat is 2500 lbs. It struggles with it, any hills are pretty much a 10-15 mph drop and a down shift to 3rd gear.

Any idea of what size of tire I would to switch to achieve the same affect as the gear swap?

 

[smokeonthewater]

Re: anybody ever completed an rear axle swop?

well sorry to say you likely will still lose the same 10-15 mph on the hills but be downshifting to 4th instead of 3rd... it would help you on the takeoff tho..

 

[jeeperman]

Re: anybody ever completed an rear axle swop?

The truck is 2wd with 225/75R16 tires.
Any idea of what size of tire I would to switch to achieve the same affect as the gear swap?

Those tires should be about 28.5" rolling diameter on average.
So with that tire and the 3.21 gear, your going 58.13mph in 4th gear with 2200 engine rpm.

A tire that is 23.4" diameter would give you an idea of what a 3.90 gear would feel like.
With that tire and the 3.90 gear, your going 39.28mph in 4th gear with 2200 engine rpm.

I cheated: http://www.izook.com/gearcalc.htm