7.25" Gear change HELP

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HotRod777

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I have a 66 Dart with an orginal open 7.25" 2.93 axle. I purchased a 3.55 Motive brand ring and pinion set that they spec for 63-up Dart. There are 2 problems:
1) The pinion nut/threaded end is bigger on the new pinion (needs a bigger nut)
2) The pinion appears to be a crush sleeve style, not the shim style that the original was. The front bearing shoulder is machined much deeper on the new pinion.

I plan to order Motive's install kit so get what I need... The question is is that they show 2 kits, one is spec'd for the older D/P/Chrysler and the other is spec'd for Dakotas. Which one do I order? I don't know if I need the newer Dakota set to match the R&P I have or if I should order the older application. (I don't want to end up with an install kit full of shims only)

Please help, and thanks in advance.
 
That sounds like too many differences. I believe you have the ring and pinion for the wrong application. You need to contact Motive Gear as mentioned above.
 
Yes, there were at least three different ring and pinion variations I know of and a lot of potential interchange with the Dana 30-35 series axles. The pre ‘72 9 bolt cover small bolt pattern 7-1/4s are the hardest to find parts for. It sounds like you have a crush sleeve unit for the ‘78 or so and up swaged axle tube units.
 
HotRod777 said:
I have a 66 Dart with an original open 7.25" 2.93 axle. .
Click to expand...
Post up pictures of what you have so far. My 69 used the crush sleeve

upload_2020-7-17_21-13-18.jpeg
 
Here’s where I am so far:
The ring gear bolted right on the case. I pulled the used pinion bearing and it pressed right onto the new pinion. The yoke fits the new pinion an the pinion seal. The only difference is the shoulder on the pinion for the shims/ crush collar. I emailed and heard right back from Motive. They claim the R&P I bought will fit a 1963 and up Dodge or Plymouth but I need to use a crush collar and nut from the newer application. They said that the shape/size/machining of the pinion stem is irrelevant being only the bearings seat and ride the races. The crush collar sets against the shoulder on the stem and the back of the front bearing. This all make sense to me... BUT we will see. My local Parts store was able to order a 7/8-14 pinion nut and a crush collar for a 7.25” ifs front out of a Dakota. They will have the parts by 2:30 tomorrow. For $12 I figure it’s worth a shot. Confidence level is 50/50 at best.
 
HotRod777 said:
Here’s where I am so far:
The ring gear bolted right on the case. I pulled the used pinion bearing and it pressed right onto the new pinion. The yoke fits the new pinion an the pinion seal. The only difference is the shoulder on the pinion for the shims/ crush collar. I emailed and heard right back from Motive. They claim the R&P I bought will fit a 1963 and up Dodge or Plymouth but I need to use a crush collar and nut from the newer application. They said that the shape/size/machining of the pinion stem is irrelevant being only the bearings seat and ride the races. The crush collar sets against the shoulder on the stem and the back of the front bearing. This all make sense to me... BUT we will see. My local Parts store was able to order a 7/8-14 pinion nut and a crush collar for a 7.25” ifs front out of a Dakota. They will have the parts by 2:30 tomorrow. For $12 I figure it’s worth a shot. Confidence level is 50/50 at best.
Click to expand...

They are probably right regarding the pinion shaft......but I would still run a crush sleeve eliminator anyway. That's just "another" area for a screw up. JMO.
 
I always like to post a result in case it helps anyone else in the future. To review, I have a 7.25” with the 9 bolt irregular shaped cover that is original to a 1966 A body. I purchased a Motive brand 3.55 gear set that they spec for 1963 and up A body. The first pic shows the difference in the pinion. The old pinion is shimmed, the new one uses a crush. After talking to Motive tech they said to use the newer parts and it will work. The second pic shows the crush sleeve and nut along with the 2 boxes/part numbers that I got from the parts store. Those parts were listed for a 1999 Dakota front 7.25” IFS. Everything bolted right in, crushed correctly and I have a very good pattern. Drove the car easy (which with a slant just means drove normally) and everything seems good... no noise and the change from 2.93 to 3.55 is a huge improvement for the slant.

CC7E9A4F-5602-433F-A9A9-BD4C1EC692B9.jpeg


58C45BC6-90F1-4DC3-BDE8-FF5120BEDEB9.jpeg
 
Thanks for the follow up on this HotRod777. I have a 7.25 and have considered a swap from the 2.76 gears. I don't race the car and I've got a mild 318 so I have considered just a gear swap and hoping it works. As opposed to rear end swap, because then it would be big bolt pattern, leafsprings, shocks, driveshaft, etc.. Hope it continues to work out for you.
 
HotRod777 said:
I always like to post a result in case it helps anyone else in the future. To review, I have a 7.25” with the 9 bolt irregular shaped cover that is original to a 1966 A body. I purchased a Motive brand 3.55 gear set that they spec for 1963 and up A body. The first pic shows the difference in the pinion. The old pinion is shimmed, the new one uses a crush. After talking to Motive tech they said to use the newer parts and it will work. The second pic shows the crush sleeve and nut along with the 2 boxes/part numbers that I got from the parts store. Those parts were listed for a 1999 Dakota front 7.25” IFS. Everything bolted right in, crushed correctly and I have a very good pattern. Drove the car easy (which with a slant just means drove normally) and everything seems good... no noise and the change from 2.93 to 3.55 is a huge improvement for the slant.

View attachment 1715565092

View attachment 1715565093
Click to expand...

Any chance you got the list of part numbers that you used to make this complete swap? I have the older 7 1/4 rear in my Dart and I am wanting to do a gear swap in my car as well. Leaning 3.55 or 3.23. Sounds like you made it work.
 
Other then the 2 part numbers on the boxes shown in my pic, I bought this:
https://www.ebay.com/itm/PLATINUM-TORQUE-3-55-RING-AND-PINION-GEARSET-FITS-DODGE-CHRYSLER-7-25-inch/261641412481?fits=Make:Dodge&hash=item3ceb0b1f81:g:Ei0AAOSwNF5eXUjt
This was a genuine Motive R&P set in the original Motive colorized factory box and part number... it was just double boxed in a bigger, plain white shipping box.
The only other thing I bought is a pinion seal (which I do not have a part number for) but the local Autozone had it on the shelf and it was like $7.
I do all my work myself and I’m a big fan of not fixing what isn’t broken. I never had a problem re-using bearings that are in good condition once you look over them. All these old cars have Timkens in then and unless someone really screws up (like running it dry or getting a lot of water in the diff For a long time) the bearing can/do last forever.

I’m just a diy-er... your mileage may vary.

1969VADart said:
Any chance you got the list of part numbers that you used to make this complete swap? I have the older 7 1/4 rear in my Dart and I am wanting to do a gear swap in my car as well. Leaning 3.55 or 3.23. Sounds like you made it work.
Click to expand...
 
I bet that was an improvement! That was a big jump.
 
HotRod777 said:
Other then the 2 part numbers on the boxes shown in my pic, I bought this:
https://www.ebay.com/itm/PLATINUM-TORQUE-3-55-RING-AND-PINION-GEARSET-FITS-DODGE-CHRYSLER-7-25-inch/261641412481?fits=Make:Dodge&hash=item3ceb0b1f81:g:Ei0AAOSwNF5eXUjt
This was a genuine Motive R&P set in the original Motive colorized factory box and part number... it was just double boxed in a bigger, plain white shipping box.
The only other thing I bought is a pinion seal (which I do not have a part number for) but the local Autozone had it on the shelf and it was like $7.
I do all my work myself and I’m a big fan of not fixing what isn’t broken. I never had a problem re-using bearings that are in good condition once you look over them. All these old cars have Timkens in then and unless someone really screws up (like running it dry or getting a lot of water in the diff For a long time) the bearing can/do last forever.

I’m just a diy-er... your mileage may vary.
Click to expand...

Better good used than new Chinees.
 
Didn't have any luck with that link. All I could find was 4.10 sets for a 7.25. Sounds like too much. I have my rear diff cover off now and will be checking for any issues and hopefully be able to confirm what is in my 63 GT. I'm assuming original gears were 2.76. If all looks good, I plan to just seal it back up for now.
 
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