diff question
 

Does any one know how to tell wich ring and pinion I have. Exe speedometer speed compared to rpm. I blew up my diff, and ordered it, used from a shop, Wich found it in a junkyard some where in texas. I stated that I have a 93 manual. I know the manual and automatic have different ratios. I've called the shop and they can't tell me wich one it is for sure. The car does seem to drive different than before. Any help would be great. I dont think HP should effect this question.

it requires some custom fabbing to get the auto in a manual

it's not a straight swap

thats good news. exept I didnt state that I replaced the whole pumpkin.

Well, did they charge you for a new bearing set and setup and installation of the auto 3.90 ring and pinion, or did they just drop in the differential assembly with the manual 4.10 ring gear already on it and just check the tooth engagement and replace the shims? Your bill should tell you what they did.

Short of that, jack up the back of the car and put a mark on the driveline with a piece of chalk or whatever. Have someone rotate a wheel to turn the driveline while you watch and have them count how many rotations the wheel makes until the mark comes back around to the starting point. If it's just over 4, you've got a 4.10 ring and pinion. If it's just less than 4, you've got 3.90s.

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Short of that, jack up the back of the car and put a mark on the driveline with a piece of chalk or whatever. Have someone rotate a wheel to turn the driveline while you watch and have them count how many rotations the wheel makes until the mark comes back around to the starting point. If it's just over 4, you've got a 4.10 ring and pinion. If it's just less than 4, you've got 3.90s.[/QUOTE]


thats what I needed to know. sounds prety simple to check. My diff case was cracked in 7 places. I receaved a diff fully assembled in a crate. Also the shop didn't deal with RX-7s but had a line on were to get junked parts. I do all my own work, and have owned the car since 96. this happened after I replaced the driver side motormount with a aluminum one that I fabricated, welded and reinforced the 4 places the power plant frame had cracked, kumo victoracers, and the newer tack at joliet dragway. P.S. I still beat the cavilerthat i was racing because he broke out. lol

Evidently I misunderstood your post.

"exept I didnt state that I replaced the whole pumpkin." looked to me like you were correcting 93BlackFD's assumption that you did, which is logical in response to his post saying the auto version is not a direct swap, and therefore if it bolted right in, you have a manual differential. Since you installed the case yourself and it evidently bolted right up, I would have expected an entirely different response... something like "thanks, that means I have a manual differential". :D

jimlab as you can see from my number of posts i am a newb to this forum and forums in general. so my wording may need some practice. allthough i am not new to the rx-7. so from what you and 93blackfd have stated i must have the manual. thanks.