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1G/2G Transmission/Driveline compatibility

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RadDsm

15+ Year Contributor
1,679
23
Apr 28, 2008
Eugene, Oregon
I'm pretty sure I know the answer to this, but I didn't really find a solid answer.

Can you use/swap 2G M/T parts (trans, xfer case, rear end, etc...) to a 1G A/T?
 
A 2G 1995-1999 AWD 5-speed transmission is usable on a 1G, but it requires a few modifications to do so; all requiring the transmission to be disassembled and modified.

*The shift lever/counterweight needs modification as the shape of the lever and the shifter counterweight gets in the way of the lower radiator hose. Ideally, you would swap out the shift lever assembly for a matching 1G unit to your vehicle (1990-early 1991 = MD735587 / mid 1991-1994 = MD738539), while swapping over and keeping the 2G shift selector to match the shift rails if you are using a 1990-early 1991 shift lever. If you do not swap out the shift lever or selector or cut off the shifter counterweight, you may have shifting issues due to the shift lever throw and you will require cutting off the shifter counterweight to clear the lower radiator hose if you are using a stock 1G main water pipe or 1G cylinder head/thermostat assembly.

*There is also an extra bellhousing mounting tab that is not used. The 2G has one extra mounting point on the front of the 1995-1999 blocks.

*You will require a 2G slave cylinder to match up the mounting points on the bellhousing.

*You will require a 1G passenger-side mount and will use the 1G front/rear block mounts.

*You will require the use of the 1G speed sensor to work properly with the OEM dash/tach, so swap over the speed sensor by removing the M6 fastener (10mm bolt head) and pulling out the 2G style speed sensor, then installing your 1G style speed sensor and shorter bolt. The 1G speed sensor uses a M6x14mm bolt (MF140004) and the 2G speed sensor uses a M6x22mm bolt (MF240029).

*The 1G DSM has the same final drive ratio as a 1995-1996 transmission and does not need adjustment. The 1997-1999 transmissions use a 57-tooth front differential ring gear that results in a final drive variation if not used with a 1997-1999 transfer case. If a 1997-1999 transmission is being used in a 1G with a 1991-1996 transfer case, then you must swap out the 57-tooth ring gear for a 1991-1996 58-tooth ring gear and make sure that the output pinion shaft gear pitch and tooth thickness and angle are the same as there were variations throughout the years of manufacturing.

Again, there is more to installing it than just bolting it in, so play close and careful attention to the differences between your existing transmission and a 2G transmission. It is doable, but you do need to change things to make it funciton properly.

The transfer case is the same dimensionally for 5-speed cars from 1991-1999; there were three variations from 1990-1999 for 5-speed transfer cases. 1990 units had a complete cast aluminum transfer case housing along with having a 22-spline input sleeve to match the 1990-early 1991 22-spline output shaft on transmissions. The 1991-1999 transfer cases share their similarities in a case upgrade to a cast iron main case and a cast aluminum tailshaft housing. The 1991-1996 transfer cases are the same internally while the 1997-1999 transfer cases use a different gear ratio ring and pinion shaft. Both style late 1991-1996 and 1997-1999 share the same input receiver sleeve (23-spline unit), bearings, shim sets, gaskets, end nut, bolts, etc. Just the drive gears are different and can be swapped out to work with other units.

As for the rear diffferential, I do not believe a 2G style works as a bolt-in unit, but this is something I do not have experience with swapping on a 1G AWD auto. I am sure someone else will chime in with a proper answer concerning the question.
 
Miliman13, since you already have the 2G shell w/ a 2G rear diff you should be fine to mount in a 1G trans. The FD for the transmissions are the same, what Twicks was mentioning is that he hasn't seen a 1G shell with a 2G rear diff installed in it.
 
This would depend on the final drive. Is this a 95 96 ot 97 up? Please do not consider fabricating mounts. Use the correvt trans/bellhousing for your 2g. Final drive is the same from 90 to 96 but of course the other differences between shifters, tcases, etc are well documented.
 
Thanks rs. I also have a 6bolt in the bay. Pauly you suggest the correct bell housing based on what mating the block or because the mounts are not there? Not for nothing but if no one ever ventured past the fence there would be no DSM or 6 bolt swaps or evo brake upgrades ect... Its simple when something is more abundant you adapt to utilized what is available. My question is not personal preference but rather what will it take.


To follow, its an LSD rear end of a 98.
2nd using 1g front axels are an option or not I've read the cups, splines don't match for the 2g.


And to those who are curios I have plans to purchase a mill/laht combo machine in the future, since I will need it for robotics. I thought if there is a way to build market one kit that allows for a 1g trans in 2g shells it would do great for the community. Since 1g trannys are abundant.
 
Unless you broke a bell housing I think it would be easier to fix a trans than fabricate mounts. Many internal parts interchange so you could take a 1g trans and put the stuff inside a 2nd housing
 
Unless you broke a bell housing I think it would be easier to fix a trans than fabricate mounts. Many internal parts interchange so you could take a 1g trans and put the stuff inside a 2nd housing
thanks paul, but i think your missing the point.
i welcome any other suggestions, as i lack experience with the 1G's so if some one knows if 1g axels will fit into 2g hubs let me know. besides that i dont see much more.
 
I cant answer your question but if memory serves the axles are different lengths. Now are you just wanting to use the 1g cups? If you cant find an answer id say just try it. The job isn't that big. You might also compare part numbers in asa or caps. That is how many ovvus founf out which parts were the same over the years.
 
^^ Im back again.
Like always 1g trans+Tcase are stupid cheap and abundant in Fl over 2g any day.
As an engineering student i have access to Cnc and lathes and ect. at my research / Racing team / University .

And im trying to gather info before i spend money on a 1g trans and t case and try to adapt it to a 2g ...

Please lets cut out the personal opinions on this thread, there is to many of that already on the site..!!

Anyone experienced in this?
 
1G and 2G axles have the same spline count (25) on the outer cups/at the hubs. While I can't personally prove that they are the exact same size and profile right now, I would seriously doubt they would change the aspects of the splines if they maintained the spline count.

But hey, when in doubt, find info from someone who's done it. From: FWD Axle Differences
Ive ran 95 axles in my 1g. The length is very minimal and no enough to do any damage... I am currently running a 2g front diff and axles in my 91 case. Only difference is the spider gears.
 
Werent you already in another thread?

There are numerous differences, especially to a 1990 trans. The big difference that makes a 1g trans not go on a 2g is the bellhousing flange is different from 6-bolt to 7-bolt. The other big thing is there are three different shift levers and three different shift selectors used throughout the years. If you want to go ahead and do it because you are stubborn, then go for it. A 2g trans can fit in a 1g, you cannot just jam a 1g trans into a 2g.

I can go into many details but it isn't warranting my time to give them all to you when you have already posted in another thread and have been told it doesn't work that way. Go please find a 2g transmission, then make sure you have the proper final drive depending on your transfer case used.
 
From My understanding 1g FWD and 2g FWD use different axels
1g AWD and 2gAwd use the same axels

1g AWD and 2g AWD M/T transmissions can be interchanged. The shifter brackets that correspond with the shifter and car its in should be used. The 2g shifter arm has to be flattened out to work on the 1g.

I will be swapping a 2g trans into my 1g today i will update with anything i find later.
 
From My understanding 1g FWD and 2g FWD use different axels
1g AWD and 2gAwd use the same axels

1g AWD and 2g AWD M/T transmissions can be interchanged. The shifter brackets that correspond with the shifter and car its in should be used. The 2g shifter arm has to be flattened out to work on the 1g.

I will be swapping a 2g trans into my 1g today i will update with anything i find later.
what about a 2g auto fwd trans into a 1g dwd manual what axles do I need to buy I think that a 2g fwd I'm right or no?
 
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